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Ogée J. A step forward in the study of photosynthetic limitation by CO 2 diffusion into the mesophyll. THE NEW PHYTOLOGIST 2024. [PMID: 38887143 DOI: 10.1111/nph.19910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2024]
Affiliation(s)
- Jérôme Ogée
- INRAE, Bordeaux Science Agro, UMR 1391 ISPA, Villenave d'Ornon, 33140, France
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2
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Rao S, Liu T, Cernusak LA, Song X. Harnessing photosynthetic C 18O 16O discrimination dynamics under leaf water nonsteady state to estimate mesophyll conductance: a new, regression-based method. THE NEW PHYTOLOGIST 2024. [PMID: 38634162 DOI: 10.1111/nph.19767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2023] [Accepted: 03/27/2024] [Indexed: 04/19/2024]
Abstract
Mesophyll conductance (gm) is a crucial plant trait that can significantly limit photosynthesis. Measurement of photosynthetic C18O16O discrimination (Δ18O) has proved to be the only viable means of resolving gm in both C3 and C4 plants. However, the currently available methods to exploit Δ18O for gm estimation are error prone due to their inadequacy in constraining the degree of oxygen isotope exchange (θ) during mesophyll CO2 hydration. Here, we capitalized on experimental manipulation of leaf water isotopic dynamics to establish a novel, nonsteady state, regression-based approach for simultaneous determination of gm and θ from online Δ18O measurements. We demonstrated the methodological and theoretical robustness of this new Δ18O-gm estimation approach and showed through measurements on several C3 and C4 species that this approach can serve as a benchmark method against which to identify previously-unrecognized biases of the existing Δ18O-gm methods. Our results highlight the unique value of this nonsteady state-based approach for contributing to ongoing efforts toward quantitative understanding of mesophyll conductance for crop yield improvement and carbon cycle modeling.
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Affiliation(s)
- Sen Rao
- College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060, China
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China
| | - Tao Liu
- College of Resources, Sichuan Agricultural University, Chengdu, 611130, China
| | - Lucas A Cernusak
- College of Science and Engineering, James Cook University, Cairns, Qld, 4878, Australia
| | - Xin Song
- College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060, China
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Diao H, Cernusak LA, Saurer M, Gessler A, Siegwolf RTW, Lehmann MM. Uncoupling of stomatal conductance and photosynthesis at high temperatures: mechanistic insights from online stable isotope techniques. THE NEW PHYTOLOGIST 2024; 241:2366-2378. [PMID: 38303410 DOI: 10.1111/nph.19558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 01/12/2024] [Indexed: 02/03/2024]
Abstract
The strong covariation of temperature and vapour pressure deficit (VPD) in nature limits our understanding of the direct effects of temperature on leaf gas exchange. Stable isotopes in CO2 and H2 O vapour provide mechanistic insight into physiological and biochemical processes during leaf gas exchange. We conducted combined leaf gas exchange and online isotope discrimination measurements on four common European tree species across a leaf temperature range of 5-40°C, while maintaining a constant leaf-to-air VPD (0.8 kPa) without soil water limitation. Above the optimum temperature for photosynthesis (30°C) under the controlled environmental conditions, stomatal conductance (gs ) and net photosynthesis rate (An ) decoupled across all tested species, with gs increasing but An decreasing. During this decoupling, mesophyll conductance (cell wall, plasma membrane and chloroplast membrane conductance) consistently and significantly decreased among species; however, this reduction did not lead to reductions in CO2 concentration at the chloroplast surface and stroma. We question the conventional understanding that diffusional limitations of CO2 contribute to the reduction in photosynthesis at high temperatures. We suggest that stomata and mesophyll membranes could work strategically to facilitate transpiration cooling and CO2 supply, thus alleviating heat stress on leaf photosynthetic function, albeit at the cost of reduced water-use efficiency.
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Affiliation(s)
- Haoyu Diao
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, 8903, Switzerland
| | - Lucas A Cernusak
- College of Science and Engineering, James Cook University, Cairns, Qld, 4879, Australia
| | - Matthias Saurer
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, 8903, Switzerland
| | - Arthur Gessler
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, 8903, Switzerland
- Institute of Terrestrial Ecosystems, ETH Zurich, Zurich, 8092, Switzerland
| | - Rolf T W Siegwolf
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, 8903, Switzerland
| | - Marco M Lehmann
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, 8903, Switzerland
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Ubierna N, Holloway-Phillips MM, Wingate L, Ogée J, Busch FA, Farquhar GD. Using Carbon Stable Isotopes to Study C 3 and C 4 Photosynthesis: Models and Calculations. Methods Mol Biol 2024; 2790:163-211. [PMID: 38649572 DOI: 10.1007/978-1-0716-3790-6_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2024]
Abstract
Stable carbon isotopes are a powerful tool to study photosynthesis. Initial applications consisted of determining isotope ratios of plant biomass using mass spectrometry. Subsequently, theoretical models relating C isotope values to gas exchange characteristics were introduced and tested against instantaneous online measurements of 13C photosynthetic discrimination. Beginning in the twenty-first century, laser absorption spectroscopes with sufficient precision for determining isotope mixing ratios became commercially available. This has allowed collection of large data sets at lower cost and with unprecedented temporal resolution. More data and accompanying knowledge have permitted refinement of 13C discrimination model equations, but often at the expense of increased model complexity and difficult parametrization. This chapter describes instantaneous online measurements of 13C photosynthetic discrimination, provides recommendations for experimental setup, and presents a thorough compilation of equations available to researchers. We update our previous 2018 version of this chapter by including recently improved descriptions of (photo)respiratory processes and associated fractionations. We discuss the capabilities and limitations of the diverse 13C discrimination model equations and provide guidance for selecting the model complexity needed for different applications.
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Affiliation(s)
- Nerea Ubierna
- Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE), Unité Mixte de Recherche (UMR)1391 ISPA, Villenave D'Ornon, France
| | - Meisha-Marika Holloway-Phillips
- Research Unit of Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmendsorf, Switzerland
| | - Lisa Wingate
- Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE), Unité Mixte de Recherche (UMR)1391 ISPA, Villenave D'Ornon, France
| | - Jérôme Ogée
- Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE), Unité Mixte de Recherche (UMR)1391 ISPA, Villenave D'Ornon, France
| | - Florian A Busch
- School of Biosciences and The Birmingham Institute of Forest Research, University of Birmingham, Birmingham, UK
| | - Graham D Farquhar
- Research School of Biology, Australian National University, Canberra, ACT, Australia
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Yang Y, Ma X, Yan L, Li Y, Wei S, Teng Z, Zhang H, Tang W, Peng S, Li Y. Soil-root interface hydraulic conductance determines responses of photosynthesis to drought in rice and wheat. PLANT PHYSIOLOGY 2023; 194:376-390. [PMID: 37706538 DOI: 10.1093/plphys/kiad498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Revised: 07/28/2023] [Accepted: 08/22/2023] [Indexed: 09/15/2023]
Abstract
Rice (Oryza sativa) production consumes a huge amount of fresh water, and improvement of drought tolerance in rice is important to conserve water resources and minimize yield loss under drought. However, processes to improve drought tolerance in rice have not been fully explored, and a comparative study between rice and wheat (Triticum aestivum) is an effective method to understand the mechanisms determining drought tolerance capacity. In the present study, we applied short-term drought stress to Shanyou 63 rice and Yannong 19 wheat to create a range of water potentials and investigated the responses of gas exchange, plant hydraulic conductance, and root morphological and anatomical traits to soil drought. We found that photosynthesis in rice was more sensitive to drought stress than that in wheat, which was related to differences in the decline of stomatal conductance and plant hydraulic conductance (Kplant). The decline of Kplant under drought was mainly driven by the decrease of soil-root interface hydraulic conductance (Ki) because Ki was more sensitive to drought than root and shoot hydraulic conductance and the soil-root interface contributed to >40% of whole-plant hydraulic resistance in both crops. Root shrinkage in response to drought was more severe in rice than that in wheat, which explains the larger depression of Ki and Kplant under drought stress in rice. We concluded that the decline of Ki drives the depression of Kplant and photosynthesis in both crops, and the plasticity of root morphology and anatomy is important in determining drought tolerance capacity.
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Affiliation(s)
- Yuhan Yang
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Xiaolin Ma
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Lu Yan
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Yingchao Li
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Suhan Wei
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Zhipeng Teng
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Hong Zhang
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Wei Tang
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Shaobing Peng
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Yong Li
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, Hubei 430070, China
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
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Luo D, Huang G, Zhang Q, Zhou G, Peng S, Li Y. Plasticity of mesophyll cell density and cell wall thickness and composition play a pivotal role in regulating plant growth and photosynthesis under shading in rapeseed. ANNALS OF BOTANY 2023; 132:963-978. [PMID: 37739395 PMCID: PMC10808032 DOI: 10.1093/aob/mcad140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Accepted: 09/20/2023] [Indexed: 09/24/2023]
Abstract
BACKGROUND AND AIMS Plasticity of leaf growth and photosynthesis is an important strategy of plants to adapt to shading stress; however, their strategy of leaf development to achieve a simultaneous increase in leaf area and photosynthesis under shading remains unknown. METHODS In the present study, a pot experiment was conducted using three rapeseed genotypes of Huayouza 50 (HYZ50), Zhongshuang 11 (ZS11) and Huayouza 62 (HYZ62), and the responses of plant growth, leaf morphoanatomical traits, cell wall composition and photosynthesis to shading were investigated. KEY RESULTS Shading significantly increased leaf area per plant (LAplant) in all genotypes, but the increase in HYZ62 was greater than that in HYZ50 and ZS11. The greater increment of LAplant in HYZ62 was related to the larger decrease in leaf mass per area (LMA) and leaf density (LD), which were in turn related to less densely packed mesophyll cells and thinner cell walls (Tcw). Moreover, shading significantly increased photosynthesis in HYZ62 but significantly decreased it in HYZ50. The enhanced photosynthesis in HYZ62 was related to increased mesophyll conductance (gm) due primarily to thinner cell walls. CONCLUSIONS The data presented indicate that the different plasticity of mesophyll cell density, cell wall thickness and cell wall composition in response to shading can dramatically affect leaf growth and photosynthesis.
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Affiliation(s)
- Dongxu Luo
- Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Guanjun Huang
- Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Qiangqiang Zhang
- Rice Ecophysiology and Precise Management Laboratory, College of Agronomy, Anhui Agricultural University, Anhui 230036, China
| | - Guangsheng Zhou
- Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Shaobing Peng
- Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Yong Li
- Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
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Shu Y, Huang G, Zhang Q, Peng S, Li Y. Reduction of photosynthesis under P deficiency is mainly caused by the decreased CO 2 diffusional capacities in wheat (Triticum aestivum L.). PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2023; 198:107680. [PMID: 37031546 DOI: 10.1016/j.plaphy.2023.107680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 03/13/2023] [Accepted: 04/03/2023] [Indexed: 05/07/2023]
Abstract
Phosphorus is one of the most important essential mineral elements for plant growth and development. It has been widely recognized that phosphorus deficiency can lead to the significant declines in leaf photosynthetic rate and leaf area. However, the internal mechanism associated with the leaf anatomical traits has not been well understood. In present study, a hydroponic experiment was conducted to study the effect of phosphorus deficiency on leaf growth and photosynthesis in Jimai 22 (JM22, Triticum aestivum L.) and Suk Landarace 26 (SL26, Triticum aestivum L.). With the decrease in phosphorus concentration, leaf photosynthetic rate and leaf area in SL26 and JM22 all decreased significantly, but the decrease in leaf area occurred earlier than that in leaf photosynthetic rate. The thresholds of phosphorus concentration to maintain a high photosynthesis were 145.5 and 138.7 mg m-2, respectively, in SL26 and JM22; and they were 197.5 and 212.0 mg m-2, respectively, for leaf growth. The decrease in leaf photosynthetic rate under low P conditions was mainly caused by the lowered stomatal conductance and mesophyll conductance, and to a less extent by the decrease in biochemical capacities. The decrease in stomatal conductance was attributed to the smaller vascular bundle area, xylem conduits area and the lower leaf hydraulic conductance. However, the reduction in mesophyll conductance was not related to either the cell wall thickness or the development of chloroplast.
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Affiliation(s)
- Yu Shu
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China.
| | - Guanjun Huang
- Key Laboratory of Crop Physiology, Ecology and Genetic Breeding, Ministry of Education, School of Agricultural Sciences, Jiangxi Agricultural University, Nanchang, 330045, Jiangxi, China.
| | - Qiangqiang Zhang
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China.
| | - Shaobing Peng
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China.
| | - Yong Li
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China.
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Wang S, Han Y, Jia Y, Chen Z, Wang G. Addressing the Relationship between Leaf Nitrogen and Carbon Isotope Discrimination from the Three Levels of Community, Population and Individual. PLANTS (BASEL, SWITZERLAND) 2023; 12:1551. [PMID: 37050177 PMCID: PMC10097192 DOI: 10.3390/plants12071551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 03/30/2023] [Accepted: 03/30/2023] [Indexed: 06/19/2023]
Abstract
The carbon, nitrogen and water cycles of terrestrial ecosystems are important biogeochemical cycles. Addressing the relationship of leaf nitrogen (N) and carbon isotope discrimination (Δ) will enhance the understanding of the links between these three cycles in plant leaves because Δ can reflect time-integrated leaf-level water-use efficiency (WUE) over the period when the leaf material is produced. Previous studies have paid considerable attention to the relationship. However, these studies have not effectively eliminated the interference of environmental factors, inter-species, and inter-individual differences in this relationship, so new research is necessary. To minimize these interferences, the present work explored the relationship at the three levels of community, population, and plant individual. Three patterns of positive, negative and no relationship were observed across communities, populations, and individuals, which is dependent on environmental conditions, species, and plant individuals. The results strongly suggested that there is no general pattern for the relationship between leaf N and Δ. Furthermore, the results indicated that there is often no coupling between leaf-level long-term WUE and leaf N in the metabolic process of carbon, N and water in leaves. The main reason for the lack of this relationship is that most plants do not invest large amounts of nitrogen into photosynthesis. In addition, the present study also observed that, for most plant species, leaf N was not related to photosynthetic rate, and that variations in photosynthetic rates are mainly driven by stomatal conductance.
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Affiliation(s)
- Shuhan Wang
- Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China
- Department of Biotechonology, College of Biotechonology and Pharmceutical Engineering, Nanjing Tech University, Nanjing 211816, China
| | - Yaowen Han
- Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China
| | - Yufu Jia
- Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, China
| | - Zixun Chen
- Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China
| | - Guoan Wang
- Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China
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Xiong D. Leaf anatomy does not explain the large variability of mesophyll conductance across C 3 crop species. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2023; 113:1035-1048. [PMID: 36602006 DOI: 10.1111/tpj.16098] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Revised: 12/29/2022] [Accepted: 01/02/2023] [Indexed: 06/17/2023]
Abstract
Increasing mesophyll conductance of CO2 (gm ) is a strategy to improve photosynthesis in C3 crops. However, the relative importance of different anatomical traits in determining gm in crops is unclear. Mesophyll conductance measurements were performed on 10 crops using the online carbon isotope discrimination method and the 'variable J' method in parallel. The influences of crucial leaf anatomical traits on gm were evaluated using a one-dimensional anatomical CO2 diffusion model. The gm values measured using two independent methods were compatible, although significant differences were observed in their absolute values. Quantitative analysis showed that cell wall thickness and chloroplast stroma thickness are the most important elements along the diffusion pathway. Unexpectedly, the large variability of gm across crops was not associated with any investigated leaf anatomical traits except chloroplast thickness. The gm values estimated using the anatomical model differed remarkably from the values measured in vivo in most species. However, when the species-specific effective porosity of the cell wall and the species-specific facilitation effect of CO2 diffusion across the membrane and chloroplast stoma were taken into account, the model could output gm values very similar to those measured in vivo. These results indicate that gm variation across crops is probably also driven by the effective porosity of the cell wall and effects of facilitation of CO2 transport across the membrane and chloroplast stroma in addition to the thicknesses of the elements.
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Affiliation(s)
- Dongliang Xiong
- National Key Laboratory of Crop Genetic Improvement, Hubei Hongshan Laboratory, MOA Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
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10
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Pathare VS, DiMario RJ, Koteyeva N, Cousins AB. Mesophyll conductance response to short-term changes in pCO 2 is related to leaf anatomy and biochemistry in diverse C 4 grasses. THE NEW PHYTOLOGIST 2022; 236:1281-1295. [PMID: 35959528 PMCID: PMC9825963 DOI: 10.1111/nph.18427] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 07/31/2022] [Indexed: 06/15/2023]
Abstract
Mesophyll CO2 conductance (gm ) in C3 species responds to short-term (minutes) changes in environment potentially due to changes in leaf anatomical and biochemical properties and measurement artefacts. Compared with C3 species, there is less information on gm responses to short-term changes in environmental conditions such as partial pressure of CO2 (pCO2 ) across diverse C4 species and the potential determinants of these responses. Using 16 C4 grasses we investigated the response of gm to short-term changes in pCO2 and its relationship with leaf anatomy and biochemistry. In general, gm increased as pCO2 decreased (statistically significant increase in 12 species), with percentage increases in gm ranging from +13% to +250%. Greater increase in gm at low pCO2 was observed in species exhibiting relatively thinner mesophyll cell walls along with greater mesophyll surface area exposed to intercellular air spaces, leaf N, photosynthetic capacity and activities of phosphoenolpyruvate carboxylase and Rubisco. Species with greater CO2 responses of gm were also able to maintain their leaf water-use efficiencies (TEi ) under low CO2 . Our study advances understanding of CO2 response of gm in diverse C4 species, identifies the key leaf traits related to this response and has implications for improving C4 photosynthetic models and TEi through modification of gm .
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Affiliation(s)
- Varsha S. Pathare
- School of Biological SciencesWashington State UniversityPullmanWA99164‐4236USA
| | - Robert J. DiMario
- School of Biological SciencesWashington State UniversityPullmanWA99164‐4236USA
| | - Nuria Koteyeva
- School of Biological SciencesWashington State UniversityPullmanWA99164‐4236USA
- Laboratory of Anatomy and MorphologyV.L. Komarov Botanical Institute of the Russian Academy of Sciences197376St PetersburgRussia
| | - Asaph B. Cousins
- School of Biological SciencesWashington State UniversityPullmanWA99164‐4236USA
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11
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Huang G, Zhang Q, Yang Y, Shu Y, Ren X, Peng S, Li Y. Interspecific variation in the temperature response of mesophyll conductance is related to leaf anatomy. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 112:221-234. [PMID: 35962704 DOI: 10.1111/tpj.15942] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2022] [Revised: 07/22/2022] [Accepted: 08/10/2022] [Indexed: 06/15/2023]
Abstract
Although mesophyll conductance (gm ) is known to be sensitive to temperature (T), the mechanisms underlying the temperature response of gm are not fully understood. In particular, it has yet to be established whether interspecific variation in gm -T relationships is associated with mesophyll anatomy and vein traits. In the present study, we measured the short-term response of gm in eight crop species, and leaf water potential (Ψleaf ) in five crop species over a temperature range of 15-35°C. The considered structural parameters are surface areas of mesophyll cells and chloroplasts facing intercellular airspaces per unit leaf area (Sm and Sc ), cell wall thickness (Tcw ), and vein length per area (VLA). We detected large interspecific variations in the temperature responses of gm and Ψleaf . The activation energy for gm (Ea,gm ) was found to be positively correlated with Sc , although it showed no correlation with Tcw . In contrast, VLA was positively correlated with the slope of the linear model of Ψleaf -T (a), whereas Ea,gm was marginally correlated with VLA and a. A two-component model was subsequently used to model gm -T relationships, and the mechanisms underlying the temperature response of gm are discussed. The data presented here indicate that leaf anatomy is a major determinant of the interspecific variation in gm -T relationships.
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Affiliation(s)
- Guanjun Huang
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River
| | - Qiangqiang Zhang
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River
| | - Yuhan Yang
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River
| | - Yu Shu
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River
| | - Xifeng Ren
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Shaobing Peng
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River
| | - Yong Li
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River
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12
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Sharwood RE, Quick WP, Sargent D, Estavillo GM, Silva-Perez V, Furbank RT. Mining for allelic gold: finding genetic variation in photosynthetic traits in crops and wild relatives. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:3085-3108. [PMID: 35274686 DOI: 10.1093/jxb/erac081] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 02/28/2022] [Indexed: 06/14/2023]
Abstract
Improvement of photosynthetic traits in crops to increase yield potential and crop resilience has recently become a major breeding target. Synthetic biology and genetic technologies offer unparalleled opportunities to create new genetics for photosynthetic traits driven by existing fundamental knowledge. However, large 'gene bank' collections of germplasm comprising historical collections of crop species and their relatives offer a wealth of opportunities to find novel allelic variation in the key steps of photosynthesis, to identify new mechanisms and to accelerate genetic progress in crop breeding programmes. Here we explore the available genetic resources in food and fibre crops, strategies to selectively target allelic variation in genes underpinning key photosynthetic processes, and deployment of this variation via gene editing in modern elite material.
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Affiliation(s)
- Robert E Sharwood
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, Australia
- ARC Centre of Excellence for Translational Photosynthesis, Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - W Paul Quick
- ARC Centre of Excellence for Translational Photosynthesis, Research School of Biology, Australian National University, Canberra, ACT, Australia
- International Rice Research Institute, Los Baños, Laguna, Philippines
| | - Demi Sargent
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, Australia
| | | | | | - Robert T Furbank
- ARC Centre of Excellence for Translational Photosynthesis, Research School of Biology, Australian National University, Canberra, ACT, Australia
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13
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Huang G, Shu Y, Peng S, Li Y. Leaf photosynthesis is positively correlated with xylem and phloem areas in leaf veins in rice (Oryza sativa) plants. ANNALS OF BOTANY 2022; 129:619-631. [PMID: 35143609 PMCID: PMC9007091 DOI: 10.1093/aob/mcac020] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 02/09/2022] [Indexed: 05/23/2023]
Abstract
BACKGROUND AND AIMS Leaf structure is an important determinant of leaf photosynthesis; however, the impacts of leaf structural traits on gas exchange parameters are still not fully understood. In the present study, 11 rice genotypes were grown in pots to investigate the influence of leaf structural traits on leaf photosynthesis and hydraulic conductance (Kleaf). METHODS In this study, leaf photosynthetic rate (A), stomatal conductance (gs), mesophyll conductance and Kleaf were measured. In addition, leaf structural traits including leaf thickness (LT), leaf mass per area and leaf xylem and phloem sizes were also measured to investigate their impacts on rice photosynthesis. KEY RESULTS We found that the total area of xylem conduits per major vein (Xmajor), leaf phloem area per minor vein (Pminor) and LT were positively correlated with Kleaf, gs and A. The path analysis suggested that, however, only Pminor had a direct impact on A; Xmajor had an indirect impact on A via gs and Pminor, while LT did not show any direct or indirect impact on A. CONCLUSION This study highlighted the importance of manipulations in Xmajor and Pminor, two previously overlooked leaf traits, to improve leaf photosynthesis in rice plants.
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Affiliation(s)
- Guanjun Huang
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Yu Shu
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Shaobing Peng
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Yong Li
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
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14
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Huang G, Fang Q, Peng S, Li Y. Genotypic variation of plant biomass under nitrogen deficiency is positively correlated with conservative economic traits in wheat. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:2175-2189. [PMID: 34897456 DOI: 10.1093/jxb/erab546] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 12/11/2021] [Indexed: 06/14/2023]
Abstract
Plant functional traits, including leaf and root economic traits, are important for understanding the composition and function of ecosystems. However, plant functional traits of crop species and the relationships between them, and their responses to environmental variations are not fully understood. In the present study, the traits in the leaf and root economics spectrum (LES and RES) and plant biomass were investigated in 14 wheat genotypes grown with sufficient or limited nitrogen (N) supply. We found that N had significant impacts on the LES and RES traits and on the relationships among them. Our results generally supported the hypothesized LES, but did not support the RES or plant economics spectrum concept among wheat plants regardless of N treatment. More importantly, we found that more conservative leaf and root economic traits are beneficial for shoot biomass accumulation in wheat plants grown with limited N supply, and for the improvement in the tolerance of wheat to N stress. The data presented suggest that growth conditions should be accounted for when studying trait-to-trait relationships, and that more conservative resource use strategies could be used as promising targets for wheat breeding programs with limited N input.
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Affiliation(s)
- Guanjun Huang
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Qing Fang
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Shaobing Peng
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Yong Li
- National Key Laboratory of Crop Genetic Improvement, Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
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15
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Crawford JD, Cousins AB. Limitation of C4 photosynthesis by low carbonic anhydrase activity increases with temperature but does not influence mesophyll CO2 conductance. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:927-938. [PMID: 34698863 DOI: 10.1093/jxb/erab464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 10/23/2021] [Indexed: 06/13/2023]
Abstract
The CO2-concentrating mechanism (CCM) in C4 plants is initiated by the uptake of bicarbonate (HCO3-) via phosphoenolpyruvate carboxylase (PEPC). Generation of HCO3- for PEPC is determined by the interaction between mesophyll CO2 conductance and the hydration of CO2 to HCO3- by carbonic anhydrase (CA). Genetic reduction of CA was previously shown not to limit C4 photosynthesis under ambient atmospheric partial pressures of CO2 (pCO2). However, CA activity varies widely across C4 species and it is unknown if there are specific environmental conditions (e.g. high temperature) where CA may limit HCO3- production for C4 photosynthesis. Additionally, CA activity has been suggested to influence mesophyll conductance, but this has not been experimentally tested. We hypothesize that CA activity can limit PEPC at high temperatures, particularly at low pCO2, but does not directly influence gm. Here we tested the influence of genetically reduced CA activity on photosynthesis and gm in the C4 plant Zea mays under a range of pCO2 and temperatures. Reduced CA activity limited HCO3- production for C4 photosynthesis at low pCO2 as temperatures increased, but did not influence mesophyll conductance. Therefore, high leaf CA activity may enhance C4 photosynthesis under high temperature when stomatal conductance restricts the availability of atmospheric CO2.
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Affiliation(s)
- Joseph D Crawford
- School of Biological Sciences, Washington State University, Pullman, WA, USA
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA, USA
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16
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Liu T, Barbour MM, Yu D, Rao S, Song X. Mesophyll conductance exerts a significant limitation on photosynthesis during light induction. THE NEW PHYTOLOGIST 2022; 233:360-372. [PMID: 34601732 DOI: 10.1111/nph.17757] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 09/24/2021] [Indexed: 06/13/2023]
Abstract
Past studies have established mesophyll diffusion conductance to CO2 (gm ) as a variable and significant limitation to plant photosynthesis under steady-state conditions. However, the role of gm in influencing photosynthesis (A) during the transient period of light induction is largely unknown. We combined gas exchange measurements with laser-enabled carbon isotope discrimination measurements to assess gm during photosynthetic induction, using Arabidopsis as the measurement species. Our measurements revealed three key findings: (1) we found that the rate at which gm approached steady state during induction was not necessarily faster than the induction rate of the carboxylation process, contradictory to what has been suggested in previous studies; (2) gm displayed a strong and consistent coordination with A under both induction and steady-state settings, hinting that the mechanism driving gm -A coupling does not require physiological stability as a prerequisite; and (3) photosynthetic limitation analysis of our data revealed that when integrated over the entire induction period, the relative limitation of A imposed by gm can be as high as > 35%. The present study provides the first demonstration of the important role of gm in limiting CO2 assimilation during photosynthetic induction, thereby pointing to a need for more research attention to be devoted to gm in future induction studies.
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Affiliation(s)
- Tao Liu
- College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060, China
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China
| | - Margaret M Barbour
- Te Aka Mātuatua - School of Science, The University of Waikato, Hamilton, 3240, New Zealand
| | - Dashi Yu
- College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060, China
| | - Sen Rao
- College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060, China
| | - Xin Song
- College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060, China
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17
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Ermakova M, Osborn H, Groszmann M, Bala S, Bowerman A, McGaughey S, Byrt C, Alonso-Cantabrana H, Tyerman S, Furbank RT, Sharwood RE, von Caemmerer S. Expression of a CO 2-permeable aquaporin enhances mesophyll conductance in the C 4 species Setaria viridis. eLife 2021; 10:70095. [PMID: 34842138 PMCID: PMC8648302 DOI: 10.7554/elife.70095] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Accepted: 11/23/2021] [Indexed: 02/02/2023] Open
Abstract
A fundamental limitation of photosynthetic carbon fixation is the availability of CO2. In C4 plants, primary carboxylation occurs in mesophyll cytosol, and little is known about the role of CO2 diffusion in facilitating C4 photosynthesis. We have examined the expression, localization, and functional role of selected plasma membrane intrinsic aquaporins (PIPs) from Setaria italica (foxtail millet) and discovered that SiPIP2;7 is CO2-permeable. When ectopically expressed in mesophyll cells of Setaria viridis (green foxtail), SiPIP2;7 was localized to the plasma membrane and caused no marked changes in leaf biochemistry. Gas exchange and C18O16O discrimination measurements revealed that targeted expression of SiPIP2;7 enhanced the conductance to CO2 diffusion from the intercellular airspace to the mesophyll cytosol. Our results demonstrate that mesophyll conductance limits C4 photosynthesis at low pCO2 and that SiPIP2;7 is a functional CO2 permeable aquaporin that can improve CO2 diffusion at the airspace/mesophyll interface and enhance C4 photosynthesis.
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Affiliation(s)
- Maria Ermakova
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, Canberra, Australia
| | - Hannah Osborn
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, Canberra, Australia
| | - Michael Groszmann
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, Canberra, Australia
| | - Soumi Bala
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, Canberra, Australia
| | - Andrew Bowerman
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, Canberra, Australia
| | - Samantha McGaughey
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, Canberra, Australia
| | - Caitlin Byrt
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, Canberra, Australia
| | - Hugo Alonso-Cantabrana
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, Canberra, Australia
| | - Steve Tyerman
- ARC Centre of Excellence in Plant Energy Biology, School of Agriculture Food and Wine, University of Adelaide, Adelaide, Australia
| | - Robert T Furbank
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, Canberra, Australia
| | - Robert E Sharwood
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, Canberra, Australia.,Hawkesbury Institute for the Environment, Western Sydney University, Richmond, Australia
| | - Susanne von Caemmerer
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, Canberra, Australia
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18
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von Caemmerer S. Updating the steady-state model of C4 photosynthesis. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:6003-6017. [PMID: 34173821 PMCID: PMC8411607 DOI: 10.1093/jxb/erab266] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 06/06/2021] [Indexed: 05/22/2023]
Abstract
C4 plants play a key role in world agriculture. For example, C4 crops such as maize and sorghum are major contributors to food production in both developed and developing countries, and the C4 grasses sugarcane, miscanthus, and switchgrass are major plant sources of bioenergy. In the challenge to manipulate and enhance C4 photosynthesis, steady-state models of leaf photosynthesis provide an important tool for gas exchange analysis and thought experiments that can explore photosynthetic pathway changes. Here a previous C4 photosynthetic model developed by von Caemmerer and Furbank has been updated with new kinetic parameterization and temperature dependencies added. The parameterization was derived from experiments on the C4 monocot, Setaria viridis, which for the first time provides a cohesive parameterization. Mesophyll conductance and its temperature dependence have also been included, as this is an important step in the quantitative correlation between the initial slope of the CO2 response curve of CO2 assimilation and in vitro phosphoenolpyruvate carboxylase activity. Furthermore, the equations for chloroplast electron transport have been updated to include cyclic electron transport flow, and equations have been added to calculate the electron transport rate from measured CO2 assimilation rates.
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Affiliation(s)
- Susanne von Caemmerer
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, The Australian National University, Acton, ACT 2601, Australia
- Correspondence:
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19
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Farquhar GD, Griffani DS, Barbour MM. The effects on isotopic composition of leaf water and transpiration of adding a gas-exchange cuvette. PLANT, CELL & ENVIRONMENT 2021; 44:2844-2857. [PMID: 33938016 DOI: 10.1111/pce.14076] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 04/24/2021] [Accepted: 04/26/2021] [Indexed: 06/12/2023]
Abstract
An expression was earlier derived for the non-steady state isotopic composition of a leaf when the composition of the water entering the leaf was not necessarily the same as that of the water being transpired (Farquhar and Cernusak 2005). This was relevant to natural conditions because the associated time constant is typically sufficiently long to ensure that the leaf water composition and fluxes of the isotopologues are rarely steady. With the advent of laser-based measurements of isotopologues, leaves have been enclosed in cuvettes and time courses of fluxes recorded. The enclosure modifies the time constant by effectively increasing the resistance to the one-way gross flux out of the stomata because transpiration increases the vapour concentration within the chamber. The resistance is increased from stomatal and boundary layer in series, to stomata, boundary layer and chamber resistance, where the latter is given by the ratio of leaf area to the flow rate out of the chamber. An apparent change in concept from one-way to net flux, introduced by Song, Simonin, Loucos and Barbour (2015) is resolved, and shown to be unnecessary, but the value of their data is reinforced.
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Affiliation(s)
- Graham D Farquhar
- Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Danielle S Griffani
- Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Margaret M Barbour
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
- Te Aka Mātuatua-School of Science, The University of Waikato, Hamilton, New Zealand
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20
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Yin X, Busch FA, Struik PC, Sharkey TD. Evolution of a biochemical model of steady-state photosynthesis. PLANT, CELL & ENVIRONMENT 2021; 44:2811-2837. [PMID: 33872407 PMCID: PMC8453732 DOI: 10.1111/pce.14070] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 04/10/2021] [Accepted: 04/12/2021] [Indexed: 05/29/2023]
Abstract
On the occasion of the 40th anniversary of the publication of the landmark model by Farquhar, von Caemmerer & Berry on steady-state C3 photosynthesis (known as the "FvCB model"), we review three major further developments of the model. These include: (1) limitation by triose phosphate utilization, (2) alternative electron transport pathways, and (3) photorespiration-associated nitrogen and C1 metabolisms. We discussed the relation of the third extension with the two other extensions, and some equivalent extensions to model C4 photosynthesis. In addition, the FvCB model has been coupled with CO2 -diffusion models. We review how these extensions and integration have broadened the use of the FvCB model in understanding photosynthesis, especially with regard to bioenergetic stoichiometries associated with photosynthetic quantum yields. Based on the new insights, we present caveats in applying the FvCB model. Further research needs are highlighted.
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Affiliation(s)
- Xinyou Yin
- Centre for Crop Systems AnalysisWageningen University & ResearchWageningenThe Netherlands
| | - Florian A. Busch
- School of Biosciences and Birmingham Institute of Forest ResearchUniversity of BirminghamBirminghamUK
| | - Paul C. Struik
- Centre for Crop Systems AnalysisWageningen University & ResearchWageningenThe Netherlands
| | - Thomas D. Sharkey
- MSU‐DOE Plant Research Laboratory, Plant Resilience InstituteMichigan State UniversityEast LansingMichiganUSA
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21
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Adnew GA, Hofmann MEG, Pons TL, Koren G, Ziegler M, Lourens LJ, Röckmann T. Leaf scale quantification of the effect of photosynthetic gas exchange on Δ 47 of CO 2. Sci Rep 2021; 11:14023. [PMID: 34234170 PMCID: PMC8263724 DOI: 10.1038/s41598-021-93092-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 06/15/2021] [Indexed: 11/30/2022] Open
Abstract
The clumped isotope composition (Δ47, the anomaly of the mass 47 isotopologue relative to the abundance expected from a random isotope distribution) of CO2 has been suggested as an additional tracer for gross CO2 fluxes. However, the effect of photosynthetic gas exchange on Δ47 has not been directly determined and two indirect/conceptual studies reported contradicting results. In this study, we quantify the effect of photosynthetic gas exchange on Δ47 of CO2 using leaf cuvette experiments with one C4 and two C3 plants. The experimental results are supported by calculations with a leaf cuvette model. Our results demonstrate the important roles of the Δ47 value of CO2 entering the leaf, kinetic fractionation as CO2 diffuses into, and out of the leaf and CO2–H2O isotope exchange with leaf water. We experimentally confirm the previously suggested dependence of Δ47 of CO2 in the air surrounding a leaf on the stomatal conductance and back-diffusion flux. Gas exchange can enrich or deplete the Δ47 of CO2 depending on the Δ47 of CO2 entering the leaf and the fraction of CO2 exchanged with leaf water and diffused back to the atmosphere, but under typical ambient conditions, it will lead to a decrease in Δ47.
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Affiliation(s)
- Getachew Agmuas Adnew
- Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, The Netherlands.
| | - Magdalena E G Hofmann
- Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, The Netherlands.,Picarro B.V., 's-Hertogenbosch, The Netherlands
| | - Thijs L Pons
- Institute of Environmental Biology, Utrecht University, Utrecht, The Netherlands
| | - Gerbrand Koren
- Meteorology and Air Quality Group, Wageningen University, Wageningen, The Netherlands
| | - Martin Ziegler
- Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands
| | - Lucas J Lourens
- Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands
| | - Thomas Röckmann
- Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, The Netherlands
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22
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Sonawane BV, Koteyeva NK, Johnson DM, Cousins AB. Differences in leaf anatomy determines temperature response of leaf hydraulic and mesophyll CO 2 conductance in phylogenetically related C 4 and C 3 grass species. THE NEW PHYTOLOGIST 2021; 230:1802-1814. [PMID: 33605441 DOI: 10.1111/nph.17287] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 02/02/2021] [Indexed: 06/12/2023]
Abstract
Leaf hydraulic and mesophyll CO2 conductance are both influenced by leaf anatomical traits, however it is poorly understood how the temperature response of these conductances differs between C4 and C3 species with distinct leaf anatomy. This study investigated the temperature response of leaf hydraulic conductance (Kleaf ), stomatal (gs ) and mesophyll (gm ) conductance to CO2 , and leaf anatomical traits in phylogenetically related Panicum antidotale (C4 ) and P. bisulcatum (C3 ) grasses. The C4 species had lower hydraulic conductance outside xylem (Kox ) and Kleaf compared with the C3 species. However, the C4 species had higher gm compared with the C3 species. Traits associated with leaf water movement, Kleaf and Kox , increased with temperature more in the C3 than in the C4 species, whereas traits related to carbon uptake, Anet and gm , increased more with temperature in the C4 than the C3 species. Our findings demonstrate that, in addition to a CO2 concentrating mechanism, outside-xylem leaf anatomy in the C4 species P. antidotale favours lower water movement through the leaf and stomata that provides an additional advantage for greater leaf carbon uptake relative to water loss with increasing leaf temperature than in the C3 species P. bisulcatum.
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Affiliation(s)
- Balasaheb V Sonawane
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Nuria K Koteyeva
- Laboratory of Anatomy and Morphology, V. L. Komarov Botanical Institute of Russian Academy of Sciences, Prof. Popov Street 2, St Petersburg, 197376, Russia
| | - Daniel M Johnson
- Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30602, USA
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
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Elferjani R, Benomar L, Momayyezi M, Tognetti R, Niinemets Ü, Soolanayakanahally RY, Théroux-Rancourt G, Tosens T, Ripullone F, Bilodeau-Gauthier S, Lamhamedi MS, Calfapietra C, Lamara M. A meta-analysis of mesophyll conductance to CO2 in relation to major abiotic stresses in poplar species. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:4384-4400. [PMID: 33739415 PMCID: PMC8163042 DOI: 10.1093/jxb/erab127] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 03/17/2021] [Indexed: 05/16/2023]
Abstract
Mesophyll conductance (gm) determines the diffusion of CO2 from the substomatal cavities to the site of carboxylation in the chloroplasts and represents a critical component of the diffusive limitation of photosynthesis. In this study, we evaluated the average effect sizes of different environmental constraints on gm in Populus spp., a forest tree model. We collected raw data of 815 A-Ci response curves from 26 datasets to estimate gm, using a single curve-fitting method to alleviate method-related bias. We performed a meta-analysis to assess the effects of different abiotic stresses on gm. We found a significant increase in gm from the bottom to the top of the canopy that was concomitant with the increase of maximum rate of carboxylation and light-saturated photosynthetic rate (Amax). gm was positively associated with increases in soil moisture and nutrient availability, but was insensitive to increasing soil copper concentration and did not vary with atmospheric CO2 concentration. Our results showed that gm was strongly related to Amax and to a lesser extent to stomatal conductance (gs). Moreover, a negative exponential relationship was obtained between gm and specific leaf area, which may be used to scale-up gm within the canopy.
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Affiliation(s)
- Raed Elferjani
- Quebec Network for Reforestation and Intensive Silviculture, TELUQ University, Montreal, QC, H2S 3L5, Canada
| | - Lahcen Benomar
- Forest Research Institute, University of Quebec in Abitibi-Temiscamingue, Rouyn-Noranda, QC, J9X 5E4, Canada
- Correspondence:
| | - Mina Momayyezi
- Department of Viticulture and Enology, University of California, Davis, CA 95616, USA
| | - Roberto Tognetti
- Università degli Studi del Molise, Via De Sanctis, 86100 Campobasso, Italy
| | - Ülo Niinemets
- Estonian University of Life Sciences, Kreutzwaldi 1, 51006 Tartu, Estonia
| | | | - Guillaume Théroux-Rancourt
- Institute of Botany, University of Natural Resources and Life Sciences, Gregor-Mendel-Strasse 33, 1180 Vienna, Austria
| | - Tiina Tosens
- Estonian University of Life Sciences, Kreutzwaldi 1, 51006 Tartu, Estonia
| | | | | | - Mohammed S Lamhamedi
- Direction de la Recherche Forestière, 2700 rue Einstein, Québec, QC, G1P 3W8, Canada
| | - Carlo Calfapietra
- Institute of Agro-Environmental & Forest Biology (IBAF), National Research Council (CNR), Via Marconi 2, Porano (TR) 05010, Italy
| | - Mebarek Lamara
- Forest Research Institute, University of Quebec in Abitibi-Temiscamingue, Rouyn-Noranda, QC, J9X 5E4, Canada
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24
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Clarke VC, Danila FR, von Caemmerer S. CO 2 diffusion in tobacco: a link between mesophyll conductance and leaf anatomy. Interface Focus 2021; 11:20200040. [PMID: 33628426 PMCID: PMC7898150 DOI: 10.1098/rsfs.2020.0040] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/09/2020] [Indexed: 12/28/2022] Open
Abstract
The partial pressure of CO2 at the sites of carboxylation within chloroplasts depends on the conductance to CO2 diffusion from intercellular airspace to the sites of carboxylation, termed mesophyll conductance (gm). We investigated how gm varies with leaf age and through a tobacco (Nicotiana tabacum) canopy by combining gas exchange and carbon isotope measurements using tunable diode laser spectroscopy. We combined these measurements with the anatomical characterization of leaves. CO2 assimilation rate, A, and gm decreased as leaves aged and moved lower in the canopy and were linearly correlated. This was accompanied by large anatomical changes including an increase in leaf thickness. Chloroplast surface area exposed to the intercellular airspace per unit leaf area (Sc) also decreased lower in the canopy. Older leaves had thicker mesophyll cell walls and gm was inversely proportional to cell wall thickness. We conclude that reduced gm of older leaves lower in the canopy was associated with a reduction in Sc and a thickening of mesophyll cell walls.
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Affiliation(s)
- Victoria C Clarke
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, The Australian National University, Acton, Australian Capital Territory 2601, Australia
| | - Florence R Danila
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, The Australian National University, Acton, Australian Capital Territory 2601, Australia
| | - Susanne von Caemmerer
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, The Australian National University, Acton, Australian Capital Territory 2601, Australia
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25
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Gimeno TE, Campany CE, Drake JE, Barton CVM, Tjoelker MG, Ubierna N, Marshall JD. Whole-tree mesophyll conductance reconciles isotopic and gas-exchange estimates of water-use efficiency. THE NEW PHYTOLOGIST 2021; 229:2535-2547. [PMID: 33217000 DOI: 10.1111/nph.17088] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Accepted: 11/07/2020] [Indexed: 06/11/2023]
Abstract
Photosynthetic water-use efficiency (WUE) describes the link between terrestrial carbon (C) and water cycles. Estimates of intrinsic WUE (iWUE) from gas exchange and C isotopic composition (δ13 C) differ due to an internal conductance in the leaf mesophyll (gm ) that is variable and seldom computed. We present the first direct estimates of whole-tree gm , together with iWUE from whole-tree gas exchange and δ13 C of the phloem (δ13 Cph ). We measured gas exchange, online 13 C-discrimination, and δ13 Cph monthly throughout spring, summer, and autumn in Eucalyptus tereticornis grown in large whole-tree chambers. Six trees were grown at ambient temperatures and six at a 3°C warmer air temperature; a late-summer drought was also imposed. Drought reduced whole-tree gm . Warming had few direct effects, but amplified drought-induced reductions in whole-tree gm . Whole-tree gm was similar to leaf gm for these same trees. iWUE estimates from δ13 Cph agreed with iWUE from gas exchange, but only after incorporating gm . δ13 Cph was also correlated with whole-tree 13 C-discrimination, but offset by -2.5 ± 0.7‰, presumably due to post-photosynthetic fractionations. We conclude that δ13 Cph is a good proxy for whole-tree iWUE, with the caveats that post-photosynthetic fractionations and intrinsic variability of gm should be incorporated to provide reliable estimates of this trait in response to abiotic stress.
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Affiliation(s)
- Teresa E Gimeno
- Basque Centre for Climate Change (BC3), Leioa, 48940, Spain
- IKERBASQUE, Basque Foundation for Science, Bilbao, 48008, Spain
| | - Courtney E Campany
- Department of Biology, Shepherd University, Shepherdstown, WV, 25443, USA
| | - John E Drake
- Forest and Natural Resources Management, SUNY-ESF, Syracuse, NY, 132110, USA
| | - Craig V M Barton
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, 2751, Australia
| | - Mark G Tjoelker
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, 2751, Australia
| | - Nerea Ubierna
- Research School of Biology, The Australian National University, Acton, ACT, 2601, Australia
| | - John D Marshall
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Skogsmarksgränd 17, 907 36, Umeå, Sweden
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26
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Evans JR. Mesophyll conductance: walls, membranes and spatial complexity. THE NEW PHYTOLOGIST 2021; 229:1864-1876. [PMID: 33135193 DOI: 10.1111/nph.16968] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 08/28/2020] [Indexed: 06/11/2023]
Abstract
A significant resistance to CO2 diffusion is imposed by mesophyll tissue inside leaves. Mesophyll resistance, rm (or its reciprocal, mesophyll conductance, gm ), reduces the rate at which Rubisco can fix CO2 , increasing the water and nitrogen costs of carbon acquisition. gm varies in proportion to the surface area of chloroplasts exposed to intercellular airspace per unit leaf area. It also depends on the thickness and effective porosity of the cell wall and the CO2 permeabilities of membranes. As no measurements exist for the effective porosity of mesophyll cell walls, and CO2 permeability values are too low to account for observed rates of CO2 assimilation, conclusions from modelling must be treated with caution. There is great variation in the mesophyll resistance per unit chloroplast area for a given cell wall thickness, which may reflect differences in effective porosity. While apparent gm can vary with CO2 and irradiance, the underlying conductance at the cellular level may remain unchanged. Dynamic changes in apparent gm arise for spatial reasons and because chloroplasts differ in their photosynthetic composition and operate in different light environments. Measurements of the temperature sensitivity of membrane CO2 permeability are urgently needed to explain variation in temperature responses of gm .
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Affiliation(s)
- John R Evans
- ARC Centre of Excellence for Translational Photosynthesis, Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
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27
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Pignon CP, Long SP. Retrospective analysis of biochemical limitations to photosynthesis in 49 species: C 4 crops appear still adapted to pre-industrial atmospheric [CO 2 ]. PLANT, CELL & ENVIRONMENT 2020; 43:2606-2622. [PMID: 32743797 DOI: 10.1111/pce.13863] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2020] [Revised: 06/23/2020] [Accepted: 07/24/2020] [Indexed: 06/11/2023]
Abstract
Leaf CO2 uptake (A) in C4 photosynthesis is limited by the maximum apparent rate of PEPc carboxylation (Vpmax ) at low intercellular [CO2 ] (ci ) with a sharp transition to a ci -saturated rate (Vmax ) due to co-limitation by ribulose-1:5-bisphosphate carboxylase/oxygenase (Rubisco) and regeneration of PEP. The response of A to ci has been widely used to determine these two parameters. Vmax and Vpmax depend on different enzymes but draw on a shared pool of leaf resources, such that resource distribution is optimized, and A maximized, when Vmax and Vpmax are co-limiting. We collected published A/ci curves in 49 C4 species and assessed variation in photosynthetic traits between phylogenetic groups, and as a function of atmospheric [CO2 ]. The balance of Vmax -Vpmax varied among evolutionary lineages and C4 subtypes. Operating A was strongly Vmax -limited, such that re-allocation of resources from Vpmax towards Vmax was predicted to improve A by 12% in C4 crops. This would not require additional inputs but rather altered partitioning of existing leaf nutrients, resulting in increased water and nutrient-use efficiency. Optimal partitioning was achieved only in plants grown at pre-industrial atmospheric [CO2 ], suggesting C4 crops have not adjusted to the rapid increase in atmospheric [CO2 ] of the past few decades.
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Affiliation(s)
- Charles P Pignon
- Carl Woese Institute for Genomic Biology and Departments of Crop Sciences and Plant Biology, University of Illinois, Urbana, Illinois, USA
| | - Stephen P Long
- Carl Woese Institute for Genomic Biology and Departments of Crop Sciences and Plant Biology, University of Illinois, Urbana, Illinois, USA
- Lancaster Environment Centre, University of Lancaster, UK
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28
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Crous KY, Campany C, Lopez R, Cano FJ, Ellsworth DS. Canopy position affects photosynthesis and anatomy in mature Eucalyptus trees in elevated CO2. TREE PHYSIOLOGY 2020; 41:tpaa117. [PMID: 32918811 DOI: 10.1093/treephys/tpaa117] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Revised: 08/26/2020] [Accepted: 09/10/2020] [Indexed: 06/11/2023]
Abstract
Leaves are exposed to different light conditions according to their canopy position, resulting in structural and anatomical differences with consequences for carbon uptake. While these structure-function relationships have been thoroughly explored in dense forest canopies, such gradients may be diminished in open canopies, and they are often ignored in ecosystem models. We tested within-canopy differences in photosynthetic properties and structural traits in leaves in a mature Eucalyptus tereticornis canopy exposed to long-term elevated CO2 for up to three years. We explored these traits in relation to anatomical variation and diffusive processes for CO2 (i.e., stomatal conductance, gs and mesophyll conductance, gm) in both upper and lower portions of the canopy receiving ambient and elevated CO2. While shade resulted in 13% lower leaf mass per area ratio (MA) in lower versus upper canopy leaves, there was no relationship between leaf Nmass and canopy gap fraction. Both maximum carboxylation capacity (Vcmax) and maximum electron transport (Jmax) were ~ 18% lower in shaded leaves and were also reduced by ~ 22% with leaf aging. In mature leaves, we found no canopy differences for gm or gs, despite anatomical differences in MA, leaf thickness and mean mesophyll thickness between canopy positions. There was a positive relationship between net photosynthesis and gm or gs in mature leaves. Mesophyll conductance was negatively correlated with mean parenchyma length, suggesting that long palisade cells may contribute to a longer CO2 diffusional pathway and more resistance to CO2 transfer to chloroplasts. Few other relationships between gm and anatomical variables were found in mature leaves, which may be due to the open crown of Eucalyptus. Consideration of shade effects and leaf-age dependent responses to photosynthetic capacity and mesophyll conductance are critical to improve canopy photosynthesis models and will improve understanding of long-term responses to elevated CO2 in tree canopies.
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Affiliation(s)
- K Y Crous
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith NSW 2751, Australia
| | - C Campany
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith NSW 2751, Australia
- Department of Biology, Shepherd University, P.O. Box 5000, Shepherdstown, West Virginia, 25443, USA
| | - R Lopez
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith NSW 2751, Australia
- Departamento de Sistemas y Recursos Naturales, Universidad Politécnica de Madrid, 28040 Madrid, Spain
| | - F J Cano
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith NSW 2751, Australia
- ARC Centre of Excellence for Translational Photosynthesis, Western Sydney University, Locked Bag 1797, Penrith NSW 2751, Australia
| | - D S Ellsworth
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith NSW 2751, Australia
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29
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Pathare VS, Sonawane BV, Koteyeva N, Cousins AB. C 4 grasses adapted to low precipitation habitats show traits related to greater mesophyll conductance and lower leaf hydraulic conductance. PLANT, CELL & ENVIRONMENT 2020; 43:1897-1910. [PMID: 32449181 DOI: 10.1111/pce.13807] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 05/18/2020] [Indexed: 06/11/2023]
Abstract
In habitats with low water availability, a fundamental challenge for plants will be to maximize photosynthetic C-gain while minimizing transpirational water-loss. This trade-off between C-gain and water-loss can in part be achieved through the coordination of leaf-level photosynthetic and hydraulic traits. To test the relationship of photosynthetic C-gain and transpirational water-loss, we grew, under common growth conditions, 18 C4 grasses adapted to habitats with different mean annual precipitation (MAP) and measured leaf-level structural and anatomical traits associated with mesophyll conductance (gm ) and leaf hydraulic conductance (Kleaf ). The C4 grasses adapted to lower MAP showed greater mesophyll surface area exposed to intercellular air spaces (Smes ) and adaxial stomatal density (SDada ) which supported greater gm . These grasses also showed greater leaf thickness and vein-to-epidermis distance, which may lead to lower Kleaf . Additionally, grasses with greater gm and lower Kleaf also showed greater photosynthetic rates (Anet ) and leaf-level water-use efficiency (WUE). In summary, we identify a suite of leaf-level traits that appear important for adaptation of C4 grasses to habitats with low MAP and may be useful to identify C4 species showing greater Anet and WUE in drier conditions.
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Affiliation(s)
- Varsha S Pathare
- School of Biological Sciences, Washington State University, Pullman, Washington, USA
| | - Balasaheb V Sonawane
- School of Biological Sciences, Washington State University, Pullman, Washington, USA
| | - Nouria Koteyeva
- School of Biological Sciences, Washington State University, Pullman, Washington, USA
- Laboratory of Anatomy and Morphology, V.L. Komarov Botanical Institute of the Russian Academy of Sciences, St. Petersburg, Russia
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, Washington, USA
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30
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Sonawane BV, Cousins AB. Mesophyll CO 2 conductance and leakiness are not responsive to short- and long-term soil water limitations in the C 4 plant Sorghum bicolor. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 103:1590-1602. [PMID: 32438487 DOI: 10.1111/tpj.14849] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 04/30/2020] [Accepted: 05/05/2020] [Indexed: 05/13/2023]
Abstract
Breeding economically important C4 crops for enhanced whole-plant water-use efficiency (WUEplant ) is needed for sustainable agriculture. WUEplant is a complex trait and an efficient phenotyping method that reports on components of WUEplant , such as intrinsic water-use efficiency (WUEi , the rate of leaf CO2 assimilation relative to water loss via stomatal conductance), is needed. In C4 plants, theoretical models suggest that leaf carbon isotope composition (δ13 C), when the efficiency of the CO2 -concentrating mechanism (leakiness, ϕ) remains constant, can be used to screen for WUEi . The limited information about how ϕ responds to water limitations confines the application of δ13 C for WUEi screening of C4 crops. The current research aimed to test the response of ϕ to short- or long-term moderate water limitations, and the relationship of δ13 C with WUEi and WUEplant , by addressing potential mesophyll CO2 conductance (gm ) and biochemical limitations in the C4 plant Sorghum bicolor. We demonstrate that gm and ϕ are not responsive to short- or long-term water limitations. Additionally, δ13 C was not correlated with gas-exchange estimates of WUEi under short- and long-term water limitations, but showed a significant negative relationship with WUEplant . The observed association between the δ13 C and WUEplant suggests an intrinsic link of δ13 C with WUEi in this C4 plant, and can potentially be used as a screening tool for WUEplant in sorghum.
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Affiliation(s)
- Balasaheb V Sonawane
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
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31
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Serrano-Romero EA, Cousins AB. Cold acclimation of mesophyll conductance, bundle-sheath conductance and leakiness in Miscanthus × giganteus. THE NEW PHYTOLOGIST 2020; 226:1594-1606. [PMID: 32112409 DOI: 10.1111/nph.16503] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 02/16/2020] [Indexed: 06/10/2023]
Abstract
The cold acclimations of mesophyll conductance (gm ), bundle-sheath conductance (gbs ) and the CO2 concentrating mechanism (CCM) of C4 plants have not been well studied. Here, we estimated the temperature response of gm , gbs and leakiness (ϕ), the amount of concentrated CO2 that escapes the bundle-sheath cells, for the chilling-tolerant C4 plant Miscanthus × giganteus grown at 14 and 25°C. To estimate these parameters, we combined the C4 -enzyme-limited photosynthesis model and the Δ13 C discrimination model. These combined models were parameterised using in vitro activities of carbonic anhydrase (CA), pyruvate, phosphate dikinase (PPDK), ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), and phosphoenolpyruvate carboxylase (PEPc). Cold-grown Miscanthus plants increased in vitro activities of RuBisCO and PPDK but decreased PEPc activity compared with warm-grown plants. Mesophyll conductance and gbs responded strongly to measurement temperatures but did not differ between plants from the two growth temperatures. Furthermore, modelling showed that ϕ increased with measurement temperatures for both cold-grown and warm-grown plants, but was only marginally larger in cold-grown compared with warm-grown plants. Our results in Miscanthus support that gm and gbs are unresponsive to growth temperature and that the CCM is able to acclimate to cold through increased activity of PPDK and RuBisCO.
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Affiliation(s)
| | - Asaph B Cousins
- Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA
- School of Biological Sciences, Washington State University, Pullman, WA, 99164-4236, USA
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32
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Zhu XG, Ort DR, Parry MAJ, von Caemmerer S. A wish list for synthetic biology in photosynthesis research. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:2219-2225. [PMID: 32060550 PMCID: PMC7134917 DOI: 10.1093/jxb/eraa075] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2019] [Accepted: 02/12/2020] [Indexed: 05/02/2023]
Abstract
This perspective summarizes the presentations and discussions at the ' International Symposium on Synthetic Biology in Photosynthesis Research', which was held in Shanghai in 2018. Leveraging the current advanced understanding of photosynthetic systems, the symposium brain-stormed about the redesign and engineering of photosynthetic systems for translational goals and evaluated available new technologies/tools for synthetic biology as well as technological obstacles and new tools that would be needed to overcome them. Four major research areas for redesigning photosynthesis were identified: (i) mining natural variations of photosynthesis; (ii) coordinating photosynthesis with pathways utilizing photosynthate; (iii) reconstruction of highly efficient photosynthetic systems in non-host species; and (iv) development of new photosynthetic systems that do not exist in nature. To expedite photosynthesis synthetic biology research, an array of new technologies and community resources need to be developed, which include expanded modelling capacities, molecular engineering toolboxes, model species, and phenotyping tools.
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Affiliation(s)
- Xin-Guang Zhu
- Institute of Plant Physiology and Ecology and Center for Excellence for Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Donald R Ort
- Departments of Plant Biology and Crop Sciences, University of Illinois at Urbana Champaign, Urbana, IL, USA
| | - Martin A J Parry
- Lancaster Environment Centre, Lancaster University, Lancaster, UK
| | - Susanne von Caemmerer
- Research School of Biological Sciences, Australian National University, Acton, Australia
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33
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Yin X, van der Putten PEL, Belay D, Struik PC. Using photorespiratory oxygen response to analyse leaf mesophyll resistance. PHOTOSYNTHESIS RESEARCH 2020; 144:85-99. [PMID: 32040701 PMCID: PMC7113236 DOI: 10.1007/s11120-020-00716-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 01/27/2020] [Indexed: 05/12/2023]
Abstract
Classical approaches to estimate mesophyll conductance ignore differences in resistance components for CO2 from intercellular air spaces (IAS) and CO2 from photorespiration (F) and respiration (Rd). Consequently, mesophyll conductance apparently becomes sensitive to (photo)respiration relative to net photosynthesis, (F + Rd)/A. This sensitivity depends on several hard-to-measure anatomical properties of mesophyll cells. We developed a method to estimate the parameter m (0 ≤ m ≤ 1) that lumps these anatomical properties, using gas exchange and chlorophyll fluorescence measurements where (F + Rd)/A ratios vary. This method was applied to tomato and rice leaves measured at five O2 levels. The estimated m was 0.3 for tomato but 0.0 for rice, suggesting that classical approaches implying m = 0 work well for rice. The mesophyll conductance taking the m factor into account still responded to irradiance, CO2, and O2 levels, similar to response patterns of stomatal conductance to these variables. Largely due to different m values, the fraction of (photo)respired CO2 being refixed within mesophyll cells was lower in tomato than in rice. But that was compensated for by the higher fraction via IAS, making the total re-fixation similar for both species. These results, agreeing with CO2 compensation point estimates, support our method of effectively analysing mesophyll resistance.
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Affiliation(s)
- Xinyou Yin
- Centre for Crop Systems Analysis, Wageningen University & Research, P.O. Box 430, 6700 AK, Wageningen, The Netherlands.
| | - Peter E L van der Putten
- Centre for Crop Systems Analysis, Wageningen University & Research, P.O. Box 430, 6700 AK, Wageningen, The Netherlands
| | - Daniel Belay
- Selale University, P.O. Box 245, Fiche, Ethiopia
| | - Paul C Struik
- Centre for Crop Systems Analysis, Wageningen University & Research, P.O. Box 430, 6700 AK, Wageningen, The Netherlands
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34
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Mesophyll conductance: the leaf corridors for photosynthesis. Biochem Soc Trans 2020; 48:429-439. [DOI: 10.1042/bst20190312] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 01/25/2020] [Accepted: 01/30/2020] [Indexed: 12/15/2022]
Abstract
Besides stomata, the photosynthetic CO2 pathway also involves the transport of CO2 from the sub-stomatal air spaces inside to the carboxylation sites in the chloroplast stroma, where Rubisco is located. This pathway is far to be a simple and direct way, formed by series of consecutive barriers that the CO2 should cross to be finally assimilated in photosynthesis, known as the mesophyll conductance (gm). Therefore, the gm reflects the pathway through different air, water and biophysical barriers within the leaf tissues and cell structures. Currently, it is known that gm can impose the same level of limitation (or even higher depending of the conditions) to photosynthesis than the wider known stomata or biochemistry. In this mini-review, we are focused on each of the gm determinants to summarize the current knowledge on the mechanisms driving gm from anatomical to metabolic and biochemical perspectives. Special attention deserve the latest studies demonstrating the importance of the molecular mechanisms driving anatomical traits as cell wall and the chloroplast surface exposed to the mesophyll airspaces (Sc/S) that significantly constrain gm. However, even considering these recent discoveries, still is poorly understood the mechanisms about signaling pathways linking the environment a/biotic stressors with gm responses. Thus, considering the main role of gm as a major driver of the CO2 availability at the carboxylation sites, future studies into these aspects will help us to understand photosynthesis responses in a global change framework.
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35
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Li Y, Song X, Li S, Salter WT, Barbour MM. The role of leaf water potential in the temperature response of mesophyll conductance. THE NEW PHYTOLOGIST 2020; 225:1193-1205. [PMID: 31545519 DOI: 10.1111/nph.16214] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 09/14/2019] [Indexed: 06/10/2023]
Abstract
Variation in temperature (T) is usually accompanied by changes in leaf water potential (Ψleaf ), which may influence mesophyll conductance (gm ). However, the effects of Ψleaf on gm have not yet been considered in models of the gm response to temperature. Temperature responses of gm and Ψleaf and the response of gm to Ψleaf were studied in rice (Oryza sativa) and wheat (Triticum aestivum), and then an empirical model of Ψleaf was incorporated into an existing gm -T model. In wheat, Ψleaf was dramatically decreased with increasing T, whereas in rice Ψleaf was less sensitive or insensitive to T. Without taking Ψleaf into account, gm for wheat showed no response to T. However, at a given Ψleaf , gm was significantly higher at high temperature compared with low. After incorporating the function of Ψleaf into the gm -T model, we suggest that the gm -T relationship can be influenced by the activation and deactivation energy for membrane permeability, Ψleaf gradient between temperatures, and the sensitivity of gm to Ψleaf , below a threshold (Ψleaf,0 ). The data presented here suggest that Ψleaf plays an important role in the gm -T relationship and should be considered in future studies related to the temperature response of gm and photosynthesis.
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Affiliation(s)
- Yong Li
- Ministry of Agriculture Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Xin Song
- College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong, 518000, China
| | - Si Li
- School of Life and Environmental Sciences, Sydney Institute of Agriculture, The University of Sydney, Sydney, 2570, NSW, Australia
| | - William T Salter
- School of Life and Environmental Sciences, Sydney Institute of Agriculture, The University of Sydney, Sydney, 2570, NSW, Australia
| | - Margaret M Barbour
- School of Life and Environmental Sciences, Sydney Institute of Agriculture, The University of Sydney, Sydney, 2570, NSW, Australia
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36
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Lundgren MR, Fleming AJ. Cellular perspectives for improving mesophyll conductance. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 101:845-857. [PMID: 31854030 PMCID: PMC7065256 DOI: 10.1111/tpj.14656] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 12/11/2019] [Indexed: 05/04/2023]
Abstract
After entering the leaf, CO2 faces an intricate pathway to the site of photosynthetic fixation embedded within the chloroplasts. The efficiency of CO2 flux is hindered by a number of structural and biochemical barriers which, together, define the ease of flow of the gas within the leaf, termed mesophyll conductance. Previous authors have identified the key elements of this pathway, raising the prospect of engineering the system to improve CO2 flux and, thus, to increase leaf photosynthetic efficiency. In this review, we provide a perspective on the potential for improving the individual elements that contribute to this complex parameter. We lay particular emphasis on generation of the cellular architecture of the leaf which sets the initial boundaries of a number of mesophyll conductance parameters, incorporating an overview of the molecular transport processes which have been proposed as major facilitators of CO2 flux across structural boundaries along the pathway. The review highlights the research areas where future effort might be invested to increase our fundamental understanding of mesophyll conductance and leaf function and, consequently, to enable translation of these findings to improve the efficiency of crop photosynthesis.
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Affiliation(s)
| | - Andrew J. Fleming
- Department of Animal and Plant SciencesUniversity of SheffieldWestern BankSheffieldS10 2TNUK
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37
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Cousins AB, Mullendore DL, Sonawane BV. Recent developments in mesophyll conductance in C3, C4, and crassulacean acid metabolism plants. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 101:816-830. [PMID: 31960507 DOI: 10.1111/tpj.14664] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Accepted: 12/19/2019] [Indexed: 05/24/2023]
Abstract
The conductance of carbon dioxide (CO2 ) from the substomatal cavities to the initial sites of CO2 fixation (gm ) can significantly reduce the availability of CO2 for photosynthesis. There have been many recent reviews on: (i) the importance of gm for accurately modelling net rates of CO2 assimilation, (ii) on how leaf biochemical and anatomical factors influence gm , (iii) the technical limitation of estimating gm , which cannot be directly measured, and (iv) how gm responds to long- and short-term changes in growth and measurement environmental conditions. Therefore, this review will highlight these previous publications but will attempt not to repeat what has already been published. We will instead initially focus on the recent developments on the two-resistance model of gm that describe the potential of photorespiratory and respiratory CO2 released within the mitochondria to diffuse directly into both the chloroplast and the cytosol. Subsequently, we summarize recent developments in the three-dimensional (3-D) reaction-diffusion models and 3-D image analysis that are providing new insights into how the complex structure and organization of the leaf influences gm . Finally, because most of the reviews and literature on gm have traditionally focused on C3 plants we review in the final sections some of the recent developments, current understanding and measurement techniques of gm in C4 and crassulacean acid metabolism (CAM) plants. These plants have both specialized leaf anatomy and either a spatially or temporally separated CO2 concentrating mechanisms (C4 and CAM, respectively) that influence how we interpret and estimate gm compared with a C3 plants.
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Affiliation(s)
- Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Daniel L Mullendore
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Balasaheb V Sonawane
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
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38
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Knauer J, Zaehle S, De Kauwe MG, Haverd V, Reichstein M, Sun Y. Mesophyll conductance in land surface models: effects on photosynthesis and transpiration. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 101:858-873. [PMID: 31659806 DOI: 10.1111/tpj.14587] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 10/10/2019] [Accepted: 10/17/2019] [Indexed: 05/08/2023]
Abstract
The CO2 transfer conductance within plant leaves (mesophyll conductance, gm ) is currently not considered explicitly in most land surface models (LSMs), but instead treated implicitly as an intrinsic property of the photosynthetic machinery. Here, we review approaches to overcome this model deficiency by explicitly accounting for gm , which comprises the re-adjustment of photosynthetic parameters and a model describing the variation of gm in dependence of environmental conditions. An explicit representation of gm causes changes in the response of photosynthesis to environmental factors, foremost leaf temperature, and ambient CO2 concentration, which are most pronounced when gm is small. These changes in leaf-level photosynthesis translate into a stronger climate and CO2 response of gross primary productivity (GPP) and transpiration at the global scale. The results from two independent studies show consistent latitudinal patterns of these effects with biggest differences in GPP in the boreal zone (up to ~15%). Transpiration and evapotranspiration show spatially similar, but attenuated, changes compared with GPP. These changes are indirect effects of gm caused by the assumed strong coupling between stomatal conductance and photosynthesis in current LSMs. Key uncertainties in these simulations are the variation of gm with light and the robustness of its temperature response across plant types and growth conditions. Future research activities focusing on the response of gm to environmental factors and its relation to other plant traits have the potential to improve the representation of photosynthesis in LSMs and to better understand its present and future role in the Earth system.
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Affiliation(s)
- Jürgen Knauer
- CSIRO Oceans and Atmosphere, Canberra, ACT, 2601, Australia
- Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, 07745, Jena, Germany
| | - Sönke Zaehle
- Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, 07745, Jena, Germany
- Michael-Stifel Center Jena for Data-Driven and Simulation Science, 07745, Jena, Germany
| | - Martin G De Kauwe
- ARC Centre of Excellence for Climate Extremes and the Climate Change Research Centre, University of New South Wales, Sydney, 2052, NSW, Australia
| | - Vanessa Haverd
- CSIRO Oceans and Atmosphere, Canberra, ACT, 2601, Australia
| | - Markus Reichstein
- Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, 07745, Jena, Germany
- Michael-Stifel Center Jena for Data-Driven and Simulation Science, 07745, Jena, Germany
| | - Ying Sun
- School of Integrative Plant Science, Soil and Crop Sciences Section, Cornell University, Ithaca, NY, 14850, USA
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Pathare VS, Koteyeva N, Cousins AB. Increased adaxial stomatal density is associated with greater mesophyll surface area exposed to intercellular air spaces and mesophyll conductance in diverse C 4 grasses. THE NEW PHYTOLOGIST 2020; 225:169-182. [PMID: 31400232 DOI: 10.1111/nph.16106] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Accepted: 08/01/2019] [Indexed: 05/21/2023]
Abstract
Mesophyll conductance (gm ) is the diffusion of CO2 from intercellular air spaces (IAS) to the first site of carboxylation in the mesophyll cells. In C3 species, gm is influenced by diverse leaf structural and anatomical traits; however, little is known about traits affecting gm in C4 species. To address this knowledge gap, we used online oxygen isotope discrimination measurements to estimate gm and microscopy techniques to measure leaf structural and anatomical traits potentially related to gm in 18 C4 grasses. In this study, gm scaled positively with photosynthesis and intrinsic water-use efficiency (TEi ), but not with stomatal conductance. Also, gm was not determined by a single trait but was positively correlated with adaxial stomatal densities (SDada ), stomatal ratio (SR), mesophyll surface area exposed to IAS (Smes ) and leaf thickness. However, gm was not related to abaxial stomatal densities (SDaba ) and mesophyll cell wall thickness (TCW ). Our study suggests that greater SDada and SR increased gm by increasing Smes and creating additional parallel pathways for CO2 diffusion inside mesophyll cells. Thus, SDada , SR and Smes are important determinants of C4 -gm and could be the target traits selected or modified for achieving greater gm and TEi in C4 species.
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Affiliation(s)
- Varsha S Pathare
- School of Biological Sciences, Washington State University, Pullman, WA, 99164-4236, USA
| | - Nuria Koteyeva
- School of Biological Sciences, Washington State University, Pullman, WA, 99164-4236, USA
- Laboratory of Anatomy and Morphology, V.L. Komarov Botanical Institute of the Russian Academy of Sciences, 197376, St Petersburg, Russia
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA, 99164-4236, USA
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40
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Giuliani R, Karki S, Covshoff S, Lin HC, Coe RA, Koteyeva NK, Evans MA, Quick WP, von Caemmerer S, Furbank RT, Hibberd JM, Edwards GE, Cousins AB. Transgenic maize phosphoenolpyruvate carboxylase alters leaf-atmosphere CO 2 and 13CO 2 exchanges in Oryza sativa. PHOTOSYNTHESIS RESEARCH 2019; 142:153-167. [PMID: 31325077 PMCID: PMC6848035 DOI: 10.1007/s11120-019-00655-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 06/11/2019] [Indexed: 05/07/2023]
Abstract
The engineering process of C4 photosynthesis into C3 plants requires an increased activity of phosphoenolpyruvate carboxylase (PEPC) in the cytosol of leaf mesophyll cells. The literature varies on the physiological effect of transgenic maize (Zea mays) PEPC (ZmPEPC) leaf expression in Oryza sativa (rice). Therefore, to address this issue, leaf-atmosphere CO2 and 13CO2 exchanges were measured, both in the light (at atmospheric O2 partial pressure of 1.84 kPa and at different CO2 levels) and in the dark, in transgenic rice expressing ZmPEPC and wild-type (WT) plants. The in vitro PEPC activity was 25 times higher in the PEPC overexpressing (PEPC-OE) plants (~20% of maize) compared to the negligible activity in WT. In the PEPC-OE plants, the estimated fraction of carboxylation by PEPC (β) was ~6% and leaf net biochemical discrimination against 13CO2[Formula: see text] was ~ 2‰ lower than in WT. However, there were no differences in leaf net CO2 assimilation rates (A) between genotypes, while the leaf dark respiration rates (Rd) over three hours after light-dark transition were enhanced (~ 30%) and with a higher 13C composition [Formula: see text] in the PEPC-OE plants compared to WT. These data indicate that ZmPEPC in the PEPC-OE rice plants contributes to leaf carbon metabolism in both the light and in the dark. However, there are some factors, potentially posttranslational regulation and PEP availability, which reduce ZmPEPC activity in vivo.
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Affiliation(s)
- Rita Giuliani
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA
| | - Shanta Karki
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
| | - Sarah Covshoff
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Hsiang-Chun Lin
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
| | - Robert A Coe
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
| | - Nuria K Koteyeva
- Laboratory of Anatomy and Morphology, V.L. Komarov Botanical Institute of the Russian Academy of Sciences, Prof. Popov Street 2, St. Petersburg, Russia, 197376
| | - Marc A Evans
- Department of Mathematics and Statistics, Washington State University, Pullman, WA, 99164-3113, USA
| | - W Paul Quick
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK
| | - Susanne von Caemmerer
- Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, ACT, 0200, Australia
| | - Robert T Furbank
- Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, ACT, 0200, Australia
| | - Julian M Hibberd
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Gerald E Edwards
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA
| | - Asaph B Cousins
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA.
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41
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Zhou H, Akçay E, Helliker BR. Estimating C 4 photosynthesis parameters by fitting intensive A/C i curves. PHOTOSYNTHESIS RESEARCH 2019; 141:181-194. [PMID: 30758752 DOI: 10.1007/s11120-019-00619-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 01/21/2019] [Indexed: 06/09/2023]
Abstract
Measurements of photosynthetic assimilation rate as a function of intercellular CO2 (A/Ci curves) are widely used to estimate photosynthetic parameters for C3 species, yet few parameters have been reported for C4 plants, because of a lack of estimation methods. Here, we extend the framework of widely used estimation methods for C3 plants to build estimation tools by exclusively fitting intensive A/Ci curves (6-8 more sampling points) for C4 using three versions of photosynthesis models with different assumptions about carbonic anhydrase processes and ATP distribution. We use simulation analysis, out of sample tests, existing in vitro measurements and chlorophyll-fluorescence measurements to validate the new estimation methods. Of the five/six photosynthetic parameters obtained, sensitivity analyses show that maximal-Rubisco-carboxylation-rate, electron-transport-rate, maximal-PEP-carboxylation-rate, and carbonic-anhydrase were robust to variation in the input parameters, while day respiration and mesophyll conductance varied. Our method provides a way to estimate carbonic anhydrase activity, a new parameter, from A/Ci curves, yet also shows that models that do not explicitly consider carbonic anhydrase yield approximate results. The two photosynthesis models, differing in whether ATP could freely transport between RuBP and PEP regeneration processes yielded consistent results under high light, but they may diverge under low light intensities. Modeling results show selection for Rubisco of low specificity and high catalytic rate, low leakage of bundle sheath, and high PEPC affinity, which may further increase C4 efficiency.
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Affiliation(s)
- Haoran Zhou
- Department of Biology, University of Pennsylvania, 433 S University Ave., 314 Leidy Labs, Philadelphia, PA, 19104, USA.
| | - Erol Akçay
- Department of Biology, University of Pennsylvania, 433 S University Ave., 314 Leidy Labs, Philadelphia, PA, 19104, USA
| | - Brent R Helliker
- Department of Biology, University of Pennsylvania, 433 S University Ave., 314 Leidy Labs, Philadelphia, PA, 19104, USA
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42
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Cano FJ, Sharwood RE, Cousins AB, Ghannoum O. The role of leaf width and conductances to CO 2 in determining water use efficiency in C 4 grasses. THE NEW PHYTOLOGIST 2019; 223:1280-1295. [PMID: 31087798 DOI: 10.1111/nph.15920] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 04/28/2019] [Indexed: 05/26/2023]
Abstract
C4 plants achieve higher photosynthesis (An ) and intrinsic water use efficiency (iWUE) than C3 plants, but processes underpinning the variability in An and iWUE across the three C4 subtypes remain unclear, partly because we lack an integrated framework for quantifying the contribution of diffusional and biochemical limitations to C4 photosynthesis. We exploited the natural diversity among C4 grasses to develop an original mathematical approach for estimating eight key processes of C4 photosynthesis and their relative limitations to An . We also developed a new formulation to estimate mesophyll conductance (gm ) based on actual hydration rates of CO2 by carbonic anhydrases. We found a positive relationship between gm and iWUE and an inverse correlation with gsw among C4 grasses. We also revealed subtype-specific regulatory processes of iWUE that may be related to known anatomical traits characterising each C4 subtype. Leaf width was an important determinant of iWUE and showed significant correlations with key limitations of An , especially among NADP-ME species. In conclusion, incorporating leaf width in breeding trials may unlock new opportunities for C4 crops because the revealed negative relationship between leaf width and iWUE may translate into higher crop and canopy WUE.
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Affiliation(s)
- Francisco Javier Cano
- ARC Centre of Translational Photosynthesis and Hawkesbury Institute for the Environment, Western Sydney University, Sydney, NSW, 2753, Australia
| | - Robert E Sharwood
- ARC Centre of Translational Photosynthesis and Australian National University, Research School of Biology, Acton, ACT, 2601, Australia
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA 99164, USA
| | - Oula Ghannoum
- ARC Centre of Translational Photosynthesis and Hawkesbury Institute for the Environment, Western Sydney University, Sydney, NSW, 2753, Australia
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43
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Shrestha A, Song X, Barbour MM. The temperature response of mesophyll conductance, and its component conductances, varies between species and genotypes. PHOTOSYNTHESIS RESEARCH 2019; 141:65-82. [PMID: 30771063 DOI: 10.1007/s11120-019-00622-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Accepted: 01/25/2019] [Indexed: 05/08/2023]
Abstract
The temperature response of mesophyll conductance to CO2 diffusion (gm) has been shown to vary considerably between species but remains poorly understood. Here, we tested the hypothesis that increases in chloroplast surface area with increasing temperature, due to the formation of chloroplast protrusions, caused observed positive responses of gm to temperature. We found no evidence of chloroplast protrusions. Using simultaneous measurements of carbon and oxygen isotope discrimination during photosynthesis to separate total gm (gm13) into cell wall and plasma membrane conductance (gm18) and chloroplast membrane conductance (gcm) components, we explored the temperature response in genotypes of soybean and barley, and sunflower plants grown at differing CO2 concentrations. Differences in the temperature sensitivity of gm18 were found between genotypes and between plants grown at differing CO2 concentration but did not relate to measured anatomical features such as chloroplast surface area or cell wall thickness. The closest fit of modelled gm13 to estimated values was found when cell wall thickness was allowed to decline at higher temperatures and transpiration rates, but it remains to be tested if this decline is realistic. The temperature response of gcm (calculated from the difference between 1/gm13 and 1/gm18) varied between barley genotypes, and was best fitted by an optimal response in sunflower. Taken together, these results indicate that gm is a highly complex trait with unpredictable sensitivity to temperature that varies between species, between genotypes within a single species, with growth environment, between replicate leaves, and even with age for an individual leaf.
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Affiliation(s)
- Arjina Shrestha
- School of Life and Environmental Sciences, The University of Sydney, 380 Werombi Road, Brownlow Hill, NSW, 2570, Australia
| | - Xin Song
- School of Life and Environmental Sciences, The University of Sydney, 380 Werombi Road, Brownlow Hill, NSW, 2570, Australia
- School of Life Sciences and Oceanography, Shenzhen University, 3688 Nanhai Ave, Shenzhen, Guangdong, 518060, China
| | - Margaret M Barbour
- School of Life and Environmental Sciences, The University of Sydney, 380 Werombi Road, Brownlow Hill, NSW, 2570, Australia.
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44
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Ubierna N, Cernusak LA, Holloway-Phillips M, Busch FA, Cousins AB, Farquhar GD. Critical review: incorporating the arrangement of mitochondria and chloroplasts into models of photosynthesis and carbon isotope discrimination. PHOTOSYNTHESIS RESEARCH 2019; 141:5-31. [PMID: 30955143 DOI: 10.1007/s11120-019-00635-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2018] [Accepted: 03/07/2019] [Indexed: 06/09/2023]
Abstract
The arrangement of mitochondria and chloroplasts, together with the relative resistances of cell wall and chloroplast, determine the path of diffusion out of the leaf for (photo)respired CO2. Traditional photosynthesis models have assumed a tight arrangement of chloroplasts packed together against the cell wall with mitochondria located behind the chloroplasts, deep inside the cytosol. Accordingly, all (photo)respired CO2 must cross the chloroplast before diffusing out of the leaf. Different arrangements have recently been considered, where all or part of the (photo)respired CO2 diffuses through the cytosol without ever entering the chloroplast. Assumptions about the path for the (photo)respiratory flux are particularly relevant for the calculation of mesophyll conductance (gm). If (photo)respired CO2 can diffuse elsewhere besides the chloroplast, apparent gm is no longer a mere physical resistance but a flux-weighted variable sensitive to the ratio of (photo)respiration to net CO2 assimilation. We discuss existing photosynthesis models in conjunction with their treatment of the (photo)respiratory flux and present new equations applicable to the generalized case where (photo)respired CO2 can diffuse both into the chloroplast and through the cytosol. Additionally, we present a new generalized Δ13C model that incorporates this dual diffusion pathway. We assess how assumptions about the fate of (photo)respired CO2 affect the interpretation of photosynthetic data and the challenges it poses for the application of different models.
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Affiliation(s)
- Nerea Ubierna
- Research School of Biology, Australian National University, Acton, ACT, 2601, Australia.
| | - Lucas A Cernusak
- College of Science and Engineering, James Cook University, Cairns, QLD, Australia
| | | | - Florian A Busch
- Research School of Biology, Australian National University, Acton, ACT, 2601, Australia
| | - Asaph B Cousins
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA
| | - Graham D Farquhar
- Research School of Biology, Australian National University, Acton, ACT, 2601, Australia
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45
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Lu Z, Xie K, Pan Y, Ren T, Lu J, Wang M, Shen Q, Guo S. Potassium mediates coordination of leaf photosynthesis and hydraulic conductance by modifications of leaf anatomy. PLANT, CELL & ENVIRONMENT 2019; 42:2231-2244. [PMID: 30938459 DOI: 10.1111/pce.13553] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 03/22/2019] [Accepted: 03/26/2019] [Indexed: 06/09/2023]
Abstract
Typical symptoms of potassium deficiency, characterized as chlorosis or withered necrosis, occur concomitantly with downregulated photosynthesis and impaired leaf water transport. However, the prominent limitations and mechanisms underlying the concerted decreases of leaf photosynthesis and hydraulic conductance are poorly understood. Monocots and dicots were investigated based on responses of photosynthesis and hydraulic conductance and their components and the correlated anatomical determinants to potassium deficiency. We found a conserved pattern in which leaf photosynthesis and hydraulic conductance concurrently decreased under potassium starvation. However, monocots and dicots showed two different hydraulic-redesign strategies: Dicots tended to show a decreased minor vein density, whereas monocots reduced the size of the bundle sheath and its extensions, rather than the minor vein density; both of these strategies may restrain xylem and outside-xylem hydraulic conductance. Additionally, potassium-deprived leaves developed with fewer mesophyll cell-to-cell connections, leading to a reduced area being available for liquid-phase flow. Further quantitative analysis revealed that mesophyll conductance to CO2 and outside-xylem hydraulic resistance were the major contributors to photosynthetic limitation and increased hydraulic resistance, at more than 50% and 60%, respectively. These results emphasize the importance of potassium in the coordinated regulation of leaf photosynthesis and hydraulic conductance through modifications of leaf anatomy.
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Affiliation(s)
- Zhifeng Lu
- Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing, 210095, China
| | - Kailiu Xie
- Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing, 210095, China
| | - Yonghui Pan
- Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing, 210095, China
| | - Tao Ren
- College of Resources and Environment, Huazhong Agricultural University, Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River) Ministry of Agriculture, Wuhan, 430070, China
| | - Jianwei Lu
- College of Resources and Environment, Huazhong Agricultural University, Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River) Ministry of Agriculture, Wuhan, 430070, China
| | - Min Wang
- Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing, 210095, China
| | - Qirong Shen
- Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing, 210095, China
| | - Shiwei Guo
- Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing, 210095, China
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46
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Knauer J, Zaehle S, De Kauwe MG, Bahar NHA, Evans JR, Medlyn BE, Reichstein M, Werner C. Effects of mesophyll conductance on vegetation responses to elevated CO 2 concentrations in a land surface model. GLOBAL CHANGE BIOLOGY 2019; 25:1820-1838. [PMID: 30809890 PMCID: PMC6487956 DOI: 10.1111/gcb.14604] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 01/26/2019] [Indexed: 05/13/2023]
Abstract
Mesophyll conductance (gm ) is known to affect plant photosynthesis. However, gm is rarely explicitly considered in land surface models (LSMs), with the consequence that its role in ecosystem and large-scale carbon and water fluxes is poorly understood. In particular, the different magnitudes of gm across plant functional types (PFTs) are expected to cause spatially divergent vegetation responses to elevated CO2 concentrations. Here, an extensive literature compilation of gm across major vegetation types is used to parameterize an empirical model of gm in the LSM JSBACH and to adjust photosynthetic parameters based on simulated An - Ci curves. We demonstrate that an explicit representation of gm changes the response of photosynthesis to environmental factors, which cannot be entirely compensated by adjusting photosynthetic parameters. These altered responses lead to changes in the photosynthetic sensitivity to atmospheric CO2 concentrations which depend both on the magnitude of gm and the climatic conditions, particularly temperature. We then conducted simulations under ambient and elevated (ambient + 200 μmol/mol) CO2 concentrations for contrasting ecosystems and for historical and anticipated future climate conditions (representative concentration pathways; RCPs) globally. The gm -explicit simulations using the RCP8.5 scenario resulted in significantly higher increases in gross primary productivity (GPP) in high latitudes (+10% to + 25%), intermediate increases in temperate regions (+5% to + 15%), and slightly lower to moderately higher responses in tropical regions (-2% to +5%), which summed up to moderate GPP increases globally. Similar patterns were found for transpiration, but with a lower magnitude. Our results suggest that the effect of an explicit representation of gm is most important for simulated carbon and water fluxes in the boreal zone, where a cold climate coincides with evergreen vegetation.
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Affiliation(s)
- Jürgen Knauer
- Department of Biogeochemical IntegrationMax Planck Institute for BiogeochemistryJenaGermany
- International Max Planck Research School for Global Biogeochemical Cycles (IMPRS gBGC)JenaGermany
| | - Sönke Zaehle
- Department of Biogeochemical IntegrationMax Planck Institute for BiogeochemistryJenaGermany
- Michael‐Stifel Center Jena for Data‐Driven and Simulation ScienceJenaGermany
| | - Martin G. De Kauwe
- ARC Centre of Excellence for Climate Extremes and the Climate Change Research CentreUniversity of New South WalesSydneyNSWAustralia
| | - Nur H. A. Bahar
- ARC Centre of Excellence in Plant Energy Biology, Division of Plant SciencesResearch School of Biology, Australian National UniversityCanberraACTAustralia
| | - John R. Evans
- ARC Centre of Excellence for Translational Photosynthesis, Division of Plant SciencesResearch School of Biology, Australian National UniversityCanberraACTAustralia
| | - Belinda E. Medlyn
- Hawkesbury Institute for the EnvironmentWestern Sydney UniversityRichmondNSWAustralia
| | - Markus Reichstein
- Department of Biogeochemical IntegrationMax Planck Institute for BiogeochemistryJenaGermany
- Michael‐Stifel Center Jena for Data‐Driven and Simulation ScienceJenaGermany
| | - Christiane Werner
- Department of Ecosystem PhysiologyUniversity of FreiburgFreiburgGermany
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47
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Sonawane BV, Cousins AB. Uncertainties and limitations of using carbon-13 and oxygen-18 leaf isotope exchange to estimate the temperature response of mesophyll CO 2 conductance in C 3 plants. THE NEW PHYTOLOGIST 2019; 222:122-131. [PMID: 30394538 DOI: 10.1111/nph.15585] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 10/28/2018] [Indexed: 06/08/2023]
Abstract
The internal CO2 gradient imposed by mesophyll conductance (gm ) reduces substrate availability for C3 photosynthesis. With several assumptions, estimates of gm can be made from coupled leaf gas exchange with isoflux analysis of carbon ∆13 C-gm and oxygen in CO2 , coupled with transpired water (H2 O) ∆18 O-gm to partition gm into its biochemical and anatomical components. However, these assumptions require validation under changing leaf temperatures. To test these assumptions, we measured and modeled the temperature response (15-40°C) of ∆13 C-gm and ∆18 O-gm along with leaf biochemistry in the C3 grass Panicum bisulcatum, which has naturally low carbonic anhydrase activity. Our study suggests that assumptions regarding the extent of isotopic equilibrium (θ) between CO2 and H2 O at the site of exchange, and that the isotopic composition of the H2 O at the sites of evaporation ( δw-e18 ) and at the site of exchange ( δw-ce18 ) are similar, may lead to errors in estimating the ∆18 O-gm temperature response. The input parameters for ∆13 C-gm appear to be less sensitive to temperature. However, this needs to be tested in species with diverse carbonic anhydrase activity. Additional information on the temperature dependency of cytosolic and chloroplastic pH may clarify uncertainties used for ∆18 O-gm under changing leaf temperatures.
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Affiliation(s)
- Balasaheb V Sonawane
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
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48
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Gimeno TE, Saavedra N, Ogée J, Medlyn BE, Wingate L. A novel optimization approach incorporating non-stomatal limitations predicts stomatal behaviour in species from six plant functional types. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:1639-1651. [PMID: 30715494 PMCID: PMC6411372 DOI: 10.1093/jxb/erz020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 01/14/2019] [Indexed: 05/23/2023]
Abstract
The primary function of stomata is to minimize plant water loss while maintaining CO2 assimilation. Stomatal water loss incurs an indirect cost to photosynthesis in the form of non-stomatal limitations (NSL) via reduced carboxylation capacity (CAP) and/or mesophyll conductance (MES). Two optimal formulations for stomatal conductance (gs) arise from the assumption of each type of NSL. In reality, both NSL could coexist, but one may prevail for a given leaf ontogenetic stage or plant functional type, depending on leaf morphology. We tested the suitability of two gs formulations (CAP versus MES) on species from six plant functional types (C4 crop, C3 grass, fern, conifer, evergreen, and deciduous angiosperm trees). MES and CAP parameters (the latter proportional to the marginal water cost to carbon gain) decreased with water availability only in deciduous angiosperm trees, while there were no clear differences between leaf ontogenetic stages. Both CAP and MES formulations fit our data in most cases, particularly under low water availability. For ferns, stomata appeared to operate optimally only when subjected to water stress. Overall, the CAP formulation provided a better fit across all species, suggesting that sub-daily stomatal responses minimize NSL by reducing carboxylation capacity predominantly, regardless of leaf morphology and ontogenetic stage.
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Affiliation(s)
- Teresa E Gimeno
- INRA, UMR ISPA, Villenave d’Ornon, France
- Basque Centre for Climate Change (BC3), Leioa, Spain
- IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
| | - Noelia Saavedra
- INRA, UMR ISPA, Villenave d’Ornon, France
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
| | | | - Belinda E Medlyn
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia
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49
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Earles JM, Buckley TN, Brodersen CR, Busch FA, Cano FJ, Choat B, Evans JR, Farquhar GD, Harwood R, Huynh M, John GP, Miller ML, Rockwell FE, Sack L, Scoffoni C, Struik PC, Wu A, Yin X, Barbour MM. Embracing 3D Complexity in Leaf Carbon-Water Exchange. TRENDS IN PLANT SCIENCE 2019; 24:15-24. [PMID: 30309727 DOI: 10.1016/j.tplants.2018.09.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 09/06/2018] [Accepted: 09/11/2018] [Indexed: 06/08/2023]
Abstract
Leaves are a nexus for the exchange of water, carbon, and energy between terrestrial plants and the atmosphere. Research in recent decades has highlighted the critical importance of the underlying biophysical and anatomical determinants of CO2 and H2O transport, but a quantitative understanding of how detailed 3D leaf anatomy mediates within-leaf transport has been hindered by the lack of a consensus framework for analyzing or simulating transport and its spatial and temporal dynamics realistically, and by the difficulty of measuring within-leaf transport at the appropriate scales. We discuss how recent technological advancements now make a spatially explicit 3D leaf analysis possible, through new imaging and modeling tools that will allow us to address long-standing questions related to plant carbon-water exchange.
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Affiliation(s)
- J Mason Earles
- School of Forestry & Environmental Studies, Yale University, New Haven, CT 06511, USA; Equal contribution
| | - Thomas N Buckley
- Department of Plant Sciences, University of California Davis, CA 95916, USA; Equal contribution
| | - Craig R Brodersen
- School of Forestry & Environmental Studies, Yale University, New Haven, CT 06511, USA
| | - Florian A Busch
- Research School of Biology, Australian National University, Action, ACT 0200, Australia
| | - F Javier Cano
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW 2753, Australia
| | - Brendan Choat
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW 2753, Australia
| | - John R Evans
- Research School of Biology, Australian National University, Action, ACT 0200, Australia
| | - Graham D Farquhar
- Research School of Biology, Australian National University, Action, ACT 0200, Australia
| | | | - Minh Huynh
- University of Sydney, Sydney, NSW 2006, Australia
| | - Grace P John
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, CA 90095, USA
| | - Megan L Miller
- College of Natural Resources, University of Idaho, Moscow, ID 83844, USA
| | - Fulton E Rockwell
- Department of Organism and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Lawren Sack
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, CA 90095, USA
| | - Christine Scoffoni
- Department of Biological Sciences, California State University Los Angeles, CA 90032, USA
| | - Paul C Struik
- Department of Plant Sciences, Wageningen University, Centre for Crop Systems Analysis, 6700 AK Wageningen, The Netherlands
| | - Alex Wu
- Centre for Plant Science, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Xinyou Yin
- Department of Plant Sciences, Wageningen University, Centre for Crop Systems Analysis, 6700 AK Wageningen, The Netherlands
| | - Margaret M Barbour
- University of Sydney, Sydney, NSW 2006, Australia; www.sydney.edu.au/science/people/margaret.barbour.
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50
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Salesse-Smith CE, Sharwood RE, Busch FA, Kromdijk J, Bardal V, Stern DB. Overexpression of Rubisco subunits with RAF1 increases Rubisco content in maize. NATURE PLANTS 2018; 4:802-810. [PMID: 30287949 DOI: 10.1038/s41477-018-0252-4] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 08/15/2018] [Indexed: 05/21/2023]
Abstract
Rubisco catalyses a rate-limiting step in photosynthesis and has long been a target for improvement due to its slow turnover rate. An alternative to modifying catalytic properties of Rubisco is to increase its abundance within C4 plant chloroplasts, which might increase activity and confer a higher carbon assimilation rate. Here, we overexpress the Rubisco large (LS) and small (SS) subunits with the Rubisco assembly chaperone RUBISCO ASSEMBLY FACTOR 1 (RAF1). While overexpression of LS and/or SS had no discernable impact on Rubisco content, addition of RAF1 overexpression resulted in a >30% increase in Rubisco content. Gas exchange showed a 15% increase in CO2 assimilation (ASAT) in UBI-LSSS-RAF1 transgenic plants, which correlated with increased fresh weight and in vitro Vcmax calculations. The divergence of Rubisco content and assimilation could be accounted for by the Rubisco activation state, which decreased up to 23%, suggesting that Rubisco activase may be limiting Vcmax, and impinging on the realization of photosynthetic potential from increased Rubisco content.
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Affiliation(s)
| | - Robert E Sharwood
- Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Florian A Busch
- Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Johannes Kromdijk
- Carl R. Woese Institute for Genomic Biology, University of Illinois, Urbana, IL, USA
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