1
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Sun W, Maseyk K, Lett C, Seibt U. Restricted internal diffusion weakens transpiration-photosynthesis coupling during heatwaves: Evidence from leaf carbonyl sulphide exchange. PLANT, CELL & ENVIRONMENT 2024; 47:1813-1833. [PMID: 38321806 DOI: 10.1111/pce.14840] [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: 04/19/2023] [Revised: 11/13/2023] [Accepted: 01/22/2024] [Indexed: 02/08/2024]
Abstract
Increasingly frequent and intense heatwaves threaten ecosystem health in a warming climate. However, plant responses to heatwaves are poorly understood. A key uncertainty concerns the intensification of transpiration when heatwaves suppress photosynthesis, known as transpiration-photosynthesis decoupling. Field observations of such decoupling are scarce, and the underlying physiological mechanisms remain elusive. Here, we use carbonyl sulphide (COS) as a leaf gas exchange tracer to examine potential mechanisms leading to transpiration-photosynthesis decoupling on a coast live oak in a southern California woodland in spring 2013. We found that heatwaves suppressed both photosynthesis and leaf COS uptake but increased transpiration or sustained it at non-heatwave levels throughout the day. Despite statistically significant decoupling between transpiration and photosynthesis, stomatal sensitivity to environmental factors did not change during heatwaves. Instead, midday photosynthesis during heatwaves was restricted by internal diffusion, as indicated by the lower internal conductance to COS. Thus, increased evaporative demand and nonstomatal limitation to photosynthesis act jointly to decouple transpiration from photosynthesis without altering stomatal sensitivity. Decoupling offered limited potential cooling benefits, questioning its effectiveness for leaf thermoregulation in xeric ecosystems. We suggest that adding COS to leaf and ecosystem flux measurements helps elucidate diverse physiological mechanisms underlying transpiration-photosynthesis decoupling.
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Affiliation(s)
- Wu Sun
- Department of Global Ecology, Carnegie Institution for Science, Stanford, California, USA
| | - Kadmiel Maseyk
- School of Environment, Earth and Ecosystem Sciences, The Open University, Milton Keynes, UK
| | - Céline Lett
- Department of Environmental Research and Innovation, Luxembourg Institute of Science and Technology, Belvaux, Luxembourg
| | - Ulli Seibt
- Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, California, USA
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2
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Pathare VS, Panahabadi R, Sonawane BV, Apalla AJ, Koteyeva N, Bartley LE, Cousins AB. Altered cell wall hydroxycinnamate composition impacts leaf- and canopy-level CO2 uptake and water use in rice. PLANT PHYSIOLOGY 2023; 194:190-208. [PMID: 37503807 DOI: 10.1093/plphys/kiad428] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 06/21/2023] [Accepted: 07/11/2023] [Indexed: 07/29/2023]
Abstract
Cell wall properties play a major role in determining photosynthetic carbon uptake and water use through their impact on mesophyll conductance (CO2 diffusion from substomatal cavities into photosynthetic mesophyll cells) and leaf hydraulic conductance (water movement from xylem, through leaf tissue, to stomata). Consequently, modification of cell wall (CW) properties might help improve photosynthesis and crop water use efficiency (WUE). We tested this using 2 independent transgenic rice (Oryza sativa) lines overexpressing the rice OsAT10 gene (encoding a "BAHD" CoA acyltransferase), which alters CW hydroxycinnamic acid content (more para-coumaric acid and less ferulic acid). Plants were grown under high and low water levels, and traits related to leaf anatomy, CW composition, gas exchange, hydraulics, plant biomass, and canopy-level water use were measured. Alteration of hydroxycinnamic acid content led to statistically significant decreases in mesophyll CW thickness (-14%) and increased mesophyll conductance (+120%) and photosynthesis (+22%). However, concomitant increases in stomatal conductance negated the increased photosynthesis, resulting in no change in intrinsic WUE (ratio of photosynthesis to stomatal conductance). Leaf hydraulic conductance was also unchanged; however, transgenic plants showed small but statistically significant increases in aboveground biomass (AGB) (+12.5%) and canopy-level WUE (+8.8%; ratio of AGB to water used) and performed better under low water levels than wild-type plants. Our results demonstrate that changes in CW composition, specifically hydroxycinnamic acid content, can increase mesophyll conductance and photosynthesis in C3 cereal crops such as rice. However, attempts to improve photosynthetic WUE will need to enhance mesophyll conductance and photosynthesis while maintaining or decreasing stomatal conductance.
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Affiliation(s)
- Varsha S Pathare
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
| | - Rahele Panahabadi
- College of Agricultural. Human, and Natural Resource Sciences, Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA
| | - Balasaheb V Sonawane
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
| | - Anthony Jude Apalla
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
| | - Nuria Koteyeva
- Laboratory of Anatomy and Morphology, V.L. Komarov Botanical Institute of the Russian Academy of Sciences, 197376 St. Petersburg, Russia
| | - Laura E Bartley
- College of Agricultural. Human, and Natural Resource Sciences, Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
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3
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Montes CM, Fox C, Sanz-Sáez Á, Serbin SP, Kumagai E, Krause MD, Xavier A, Specht JE, Beavis WD, Bernacchi CJ, Diers BW, Ainsworth EA. High-throughput characterization, correlation, and mapping of leaf photosynthetic and functional traits in the soybean (Glycine max) nested association mapping population. Genetics 2022; 221:iyac065. [PMID: 35451475 PMCID: PMC9157091 DOI: 10.1093/genetics/iyac065] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Accepted: 04/03/2022] [Indexed: 11/14/2022] Open
Abstract
Photosynthesis is a key target to improve crop production in many species including soybean [Glycine max (L.) Merr.]. A challenge is that phenotyping photosynthetic traits by traditional approaches is slow and destructive. There is proof-of-concept for leaf hyperspectral reflectance as a rapid method to model photosynthetic traits. However, the crucial step of demonstrating that hyperspectral approaches can be used to advance understanding of the genetic architecture of photosynthetic traits is untested. To address this challenge, we used full-range (500-2,400 nm) leaf reflectance spectroscopy to build partial least squares regression models to estimate leaf traits, including the rate-limiting processes of photosynthesis, maximum Rubisco carboxylation rate, and maximum electron transport. In total, 11 models were produced from a diverse population of soybean sampled over multiple field seasons to estimate photosynthetic parameters, chlorophyll content, leaf carbon and leaf nitrogen percentage, and specific leaf area (with R2 from 0.56 to 0.96 and root mean square error approximately <10% of the range of calibration data). We explore the utility of these models by applying them to the soybean nested association mapping population, which showed variability in photosynthetic and leaf traits. Genetic mapping provided insights into the underlying genetic architecture of photosynthetic traits and potential improvement in soybean. Notably, the maximum Rubisco carboxylation rate mapped to a region of chromosome 19 containing genes encoding multiple small subunits of Rubisco. We also mapped the maximum electron transport rate to a region of chromosome 10 containing a fructose 1,6-bisphosphatase gene, encoding an important enzyme in the regeneration of ribulose 1,5-bisphosphate and the sucrose biosynthetic pathway. The estimated rate-limiting steps of photosynthesis were low or negatively correlated with yield suggesting that these traits are not influenced by the same genetic mechanisms and are not limiting yield in the soybean NAM population. Leaf carbon percentage, leaf nitrogen percentage, and specific leaf area showed strong correlations with yield and may be of interest in breeding programs as a proxy for yield. This work is among the first to use hyperspectral reflectance to model and map the genetic architecture of the rate-limiting steps of photosynthesis.
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Affiliation(s)
| | - Carolyn Fox
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Álvaro Sanz-Sáez
- Department of Crop, Soil, and Environmental Sciences, Auburn, AL 36849, USA
| | - Shawn P Serbin
- Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Etsushi Kumagai
- Institute of Agro-environmental Sciences, National Agriculture and Food Research Organization, Tsukuba, Ibaraki 305-8604, Japan
| | - Matheus D Krause
- Department of Agronomy, Iowa State University, Agronomy Hall, Ames, IA 50011, USA
| | - Alencar Xavier
- Department of Agronomy, Purdue University, West Lafayette, IN 47907, USA
- Department of Biostatistics, Corteva Agrisciences, Johnston, IA 50131, USA
| | - James E Specht
- Department of Agronomy and Horticulture, University of Nebraska, Lincoln, NE 68583, USA
| | - William D Beavis
- Department of Agronomy, Iowa State University, Agronomy Hall, Ames, IA 50011, USA
| | - Carl J Bernacchi
- Global Change and Photosynthesis Research Unit, USDA ARS, Urbana, IL 61801, USA
- Carl R. Woese Institute for Genomic Biology, Urbana, IL 61801, USA
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Brian W Diers
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Elizabeth A Ainsworth
- Global Change and Photosynthesis Research Unit, USDA ARS, Urbana, IL 61801, USA
- Carl R. Woese Institute for Genomic Biology, Urbana, IL 61801, USA
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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4
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Yin X, Gu J, Dingkuhn M, Struik PC. A model-guided holistic review of exploiting natural variation of photosynthesis traits in crop improvement. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:3173-3188. [PMID: 35323898 PMCID: PMC9126731 DOI: 10.1093/jxb/erac109] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 03/22/2022] [Indexed: 05/18/2023]
Abstract
Breeding for improved leaf photosynthesis is considered as a viable approach to increase crop yield. Whether it should be improved in combination with other traits has not been assessed critically. Based on the quantitative crop model GECROS that interconnects various traits to crop productivity, we review natural variation in relevant traits, from biochemical aspects of leaf photosynthesis to morpho-physiological crop characteristics. While large phenotypic variations (sometimes >2-fold) for leaf photosynthesis and its underlying biochemical parameters were reported, few quantitative trait loci (QTL) were identified, accounting for a small percentage of phenotypic variation. More QTL were reported for sink size (that feeds back on photosynthesis) or morpho-physiological traits (that affect canopy productivity and duration), together explaining a much greater percentage of their phenotypic variation. Traits for both photosynthetic rate and sustaining it during grain filling were strongly related to nitrogen-related traits. Much of the molecular basis of known photosynthesis QTL thus resides in genes controlling photosynthesis indirectly. Simulation using GECROS demonstrated the overwhelming importance of electron transport parameters, compared with the maximum Rubisco activity that largely determines the commonly studied light-saturated photosynthetic rate. Exploiting photosynthetic natural variation might significantly improve crop yield if nitrogen uptake, sink capacity, and other morpho-physiological traits are co-selected synergistically.
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Affiliation(s)
- Xinyou Yin
- Centre for Crop Systems Analysis, Wageningen University & Research, PO Box 430, 6700 AK Wageningen, The Netherlands
| | - Junfei Gu
- College of Agriculture, Yangzhou University, 48 Wenhui East Road, Yangzhou, Jiangsu 225009, China
| | | | - Paul C Struik
- Centre for Crop Systems Analysis, Wageningen University & Research, PO Box 430, 6700 AK Wageningen, The Netherlands
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Lei Z, Liu F, Wright IJ, Carriquí M, Niinemets Ü, Han J, Jia M, Atwell BJ, Cai X, Zhang W, Zhou Z, Zhang Y. Comparisons of photosynthetic and anatomical traits between wild and domesticated cotton. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:873-885. [PMID: 34153103 DOI: 10.1093/jxb/erab293] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 06/19/2021] [Indexed: 06/13/2023]
Abstract
Mesophyll conductance (gm) is a crucial leaf trait contributing to the photosynthetic rate (AN). Plant domestication typically leads to an enhancement of AN that is often associated with profound anatomical modifications, but it is unclear which of these structural alterations influence gm. We analyzed the implication of domestication on leaf anatomy and its effect on gm in 26 wild and 31 domesticated cotton genotypes (Gossypium sp.) grown under field conditions. We found that domesticated genotypes had higher AN but similar gm to wild genotypes. Consistent with this, domestication did not translate into significant differences in the fraction of mesophyll occupied by intercellular air spaces (fias) or mesophyll and chloroplast surface area exposed to intercellular air space (Sm/S and Sc/S, respectively). However, leaves of domesticated genotypes were significantly thicker, with larger but fewer mesophyll cells with thinner cell walls. Moreover, domesticated genotypes had higher cell wall conductance (gcw) but smaller cytoplasmic conductance (gcyt) than wild genotypes. It appears that domestication in cotton has not generally led to significant improvement in gm, in part because their thinner mesophyll cell walls (increasing gcw) compensate for their lower gcyt, itself due to larger distance between plasmalemma and chloroplast envelopes.
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Affiliation(s)
- Zhangying Lei
- The Key Laboratory of Oasis Eco-agriculture, Xinjiang Production and Construction Group, Shihezi University, Shihezi, 832003, PR China
- Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia
| | - Fang Liu
- State Key Laboratory of Cotton Biology, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, 455000, PR China
| | - Ian J Wright
- Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia
| | - Marc Carriquí
- School of Natural Sciences, University of Tasmania, Bag 55, 7001 Hobart, Tasmania, Australia
| | - Ülo Niinemets
- Chair of Crop Science and Plant Biology, Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Kreutzwaldi 1, 51006 Tartu, Estonia
| | - Jimei Han
- School of Integrative Plant Science, Soil and Crop Science Section, Cornell University, Ithaca, NY 14850, USA
| | - Mengmeng Jia
- The Key Laboratory of Oasis Eco-agriculture, Xinjiang Production and Construction Group, Shihezi University, Shihezi, 832003, PR China
| | - Brian J Atwell
- Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia
| | - Xiaoyan Cai
- State Key Laboratory of Cotton Biology, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, 455000, PR China
| | - Wangfeng Zhang
- The Key Laboratory of Oasis Eco-agriculture, Xinjiang Production and Construction Group, Shihezi University, Shihezi, 832003, PR China
| | - Zhongli Zhou
- State Key Laboratory of Cotton Biology, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, 455000, PR China
| | - Yali Zhang
- The Key Laboratory of Oasis Eco-agriculture, Xinjiang Production and Construction Group, Shihezi University, Shihezi, 832003, PR China
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6
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Zait Y, Ferrero‐Serrano Á, Assmann SM. The α subunit of the heterotrimeric G protein regulates mesophyll CO 2 conductance and drought tolerance in rice. THE NEW PHYTOLOGIST 2021; 232:2324-2338. [PMID: 34515342 PMCID: PMC9293471 DOI: 10.1111/nph.17730] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 09/01/2021] [Indexed: 05/03/2023]
Abstract
Mesophyll conductance gm determines CO2 diffusion rates from mesophyll intercellular air spaces to the chloroplasts and is an important factor limiting photosynthesis. Increasing gm in cultivated plants is a potential strategy to increase photosynthesis and intrinsic water use efficiency (WUEi ). The anatomy of the leaf and metabolic factors such as aquaporins and carbonic anhydrases have been identified as important determinants of gm . However, genes involved in the regulation and modulation of gm remain largely unknown. In this work, we investigated the role of heterotrimeric G proteins in gm and drought tolerance in rice d1 mutants, which harbor a null mutation in the Gα subunit gene, RGA1. d1 mutants in both cv Nipponbare and cv Taichung 65 exhibited increased gm , fostering improvement in photosynthesis, WUEi , and drought tolerance compared with wild-type. The increased surface area of mesophyll cells and chloroplasts exposed to intercellular airspaces and the reduced cell wall and chloroplast thickness in the d1 mutant are evident contributors to the increase in gm . Our results indicate that manipulation of heterotrimeric G protein signaling has the potential to improve crop WUEi and productivity under drought.
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Affiliation(s)
- Yotam Zait
- Biology DepartmentPenn State University208 Mueller LaboratoryUniversity ParkPA16802USA
| | - Ángel Ferrero‐Serrano
- Biology DepartmentPenn State University208 Mueller LaboratoryUniversity ParkPA16802USA
| | - Sarah M. Assmann
- Biology DepartmentPenn State University208 Mueller LaboratoryUniversity ParkPA16802USA
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7
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Hameed A, Ahmed MZ, Hussain T, Aziz I, Ahmad N, Gul B, Nielsen BL. Effects of Salinity Stress on Chloroplast Structure and Function. Cells 2021; 10:2023. [PMID: 34440792 PMCID: PMC8395010 DOI: 10.3390/cells10082023] [Citation(s) in RCA: 61] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 08/05/2021] [Indexed: 02/07/2023] Open
Abstract
Salinity is a growing problem affecting soils and agriculture in many parts of the world. The presence of salt in plant cells disrupts many basic metabolic processes, contributing to severe negative effects on plant development and growth. This review focuses on the effects of salinity on chloroplasts, including the structures and function of these organelles. Chloroplasts house various important biochemical reactions, including photosynthesis, most of which are considered essential for plant survival. Salinity can affect these reactions in a number of ways, for example, by changing the chloroplast size, number, lamellar organization, lipid and starch accumulation, and interfering with cross-membrane transportation. Research has shown that maintenance of the normal chloroplast physiology is necessary for the survival of the entire plant. Many plant species have evolved different mechanisms to withstand the harmful effects of salt-induced toxicity on their chloroplasts and its machinery. The differences depend on the plant species and growth stage and can be quite different between salt-sensitive (glycophyte) and salt-tolerant (halophyte) plants. Salt stress tolerance is a complex trait, and many aspects of salt tolerance in plants are not entirely clear yet. In this review, we discuss the different mechanisms of salt stress tolerance in plants with a special focus on chloroplast structure and its functions, including the underlying differences between glycophytes and halophytes.
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Affiliation(s)
- Abdul Hameed
- Dr. M. Ajmal Khan Institute for Sustainable Halophyte Utilization, University of Karachi, Sindh 75270, Pakistan; (A.H.); (M.Z.A.); (T.H.); (I.A.); (B.G.)
| | - Muhammad Zaheer Ahmed
- Dr. M. Ajmal Khan Institute for Sustainable Halophyte Utilization, University of Karachi, Sindh 75270, Pakistan; (A.H.); (M.Z.A.); (T.H.); (I.A.); (B.G.)
| | - Tabassum Hussain
- Dr. M. Ajmal Khan Institute for Sustainable Halophyte Utilization, University of Karachi, Sindh 75270, Pakistan; (A.H.); (M.Z.A.); (T.H.); (I.A.); (B.G.)
| | - Irfan Aziz
- Dr. M. Ajmal Khan Institute for Sustainable Halophyte Utilization, University of Karachi, Sindh 75270, Pakistan; (A.H.); (M.Z.A.); (T.H.); (I.A.); (B.G.)
| | - Niaz Ahmad
- Agricultural Biotechnology Division, National Institute for Biotechnology & Genetic Engineering (NIBGE), Faisalabad 44000, Pakistan;
- Department of Biotechnology, Pakistan Institute of Engineering and Applied Science (PIEAS), Islamabad 44000, Pakistan
| | - Bilquees Gul
- Dr. M. Ajmal Khan Institute for Sustainable Halophyte Utilization, University of Karachi, Sindh 75270, Pakistan; (A.H.); (M.Z.A.); (T.H.); (I.A.); (B.G.)
| | - Brent L. Nielsen
- Department of Microbiology & Molecular Biology, Brigham Young University, Provo, UT 84602, USA
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8
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Pignon CP, Leakey ADB, Long SP, Kromdijk J. Drivers of Natural Variation in Water-Use Efficiency Under Fluctuating Light Are Promising Targets for Improvement in Sorghum. FRONTIERS IN PLANT SCIENCE 2021; 12:627432. [PMID: 33597965 PMCID: PMC7882533 DOI: 10.3389/fpls.2021.627432] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 01/05/2021] [Indexed: 05/20/2023]
Abstract
Improving leaf intrinsic water-use efficiency (iWUE), the ratio of photosynthetic CO2 assimilation to stomatal conductance, could decrease crop freshwater consumption. iWUE has primarily been studied under steady-state light, but light in crop stands rapidly fluctuates. Leaf responses to these fluctuations substantially affect overall plant performance. Notably, photosynthesis responds faster than stomata to decreases in light intensity: this desynchronization results in substantial loss of iWUE. Traits that could improve iWUE under fluctuating light, such as faster stomatal movement to better synchronize stomata with photosynthesis, show significant natural diversity in C3 species. However, C4 crops have been less closely investigated. Additionally, while modification of photosynthetic or stomatal traits independent of one another will theoretically have a proportionate effect on iWUE, in reality these traits are inter-dependent. It is unclear how interactions between photosynthesis and stomata affect natural diversity in iWUE, and whether some traits are more tractable drivers to improve iWUE. Here, measurements of photosynthesis, stomatal conductance and iWUE under steady-state and fluctuating light, along with stomatal patterning, were obtained in 18 field-grown accessions of the C4 crop sorghum. These traits showed significant natural diversity but were highly correlated, with important implications for improvement of iWUE. Some features, such as gradual responses of photosynthesis to decreases in light, appeared promising for improvement of iWUE. Other traits showed tradeoffs that negated benefits to iWUE, e.g., accessions with faster stomatal responses to decreases in light, expected to benefit iWUE, also displayed more abrupt losses in photosynthesis, resulting in overall lower iWUE. Genetic engineering might be needed to break these natural tradeoffs and achieve optimal trait combinations, e.g., leaves with fewer, smaller stomata, more sensitive to changes in photosynthesis. Traits describing iWUE at steady-state, and the change in iWUE following decreases in light, were important contributors to overall iWUE under fluctuating light.
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Affiliation(s)
- Charles P. Pignon
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Andrew D. B. Leakey
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- *Correspondence: Andrew D. B. Leakey,
| | - Stephen P. Long
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Lancaster Environment Centre, Lancaster University, Lancaster, United Kingdom
| | - Johannes Kromdijk
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
- Johannes Kromdijk, ;
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9
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Batnini M, Fernández Del-Saz N, Fullana-Pericàs M, Palma F, Haddoudi I, Mrabet M, Ribas-Carbo M, Mhadhbi H. The alternative oxidase pathway is involved in optimizing photosynthesis in Medicago truncatula infected by Fusarium oxysporum and Rhizoctonia solani. PHYSIOLOGIA PLANTARUM 2020; 169:600-611. [PMID: 32108952 DOI: 10.1111/ppl.13080] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 02/13/2020] [Accepted: 02/25/2020] [Indexed: 06/10/2023]
Abstract
Phytopathogen infection alters primary metabolism status and plant development. The alternative oxidase (AOX) has been hypothesized to increase under pathogen attack preventing reductions, thus optimizing photosynthesis and growth. In this study, two genotypes of Medicago truncatula, one relatively resistant (Jemalong A17) and one susceptible (TN1.11), were infected with Fusarium oxysporum and Rhizoctonia solani. The in vivo foliar respiratory activities of the cytochrome oxidase pathway (COP) and the alternative oxidase pathway (AOP) were measured using the oxygen isotope fractionation. Gas exchange and photosynthesis-related parameters were measured and calculated together with antioxidant enzymes activities and organic acids contents. Our results show that the in vivo activity of AOX (valt ) plays a role under fungal infection. When infected with R. solani, the increase of valt in A17 was concomitant to an increase in net assimilation, in mesophyll conductance, to an improvement in the maximum velocity of Rubisco carboxylation and to unchanged malate content. However, under F. oxysporum infection, the induced valt was accompanied by an enhancement in the antioxidant enzymes, superoxide dismutase (SOD; EC1.15.1.1), catalase (CAT; EC1.11.1.6) and guaiacol peroxidase (GPX; EC1.11.1.7), activities and to an unchanged tricarboxylic acid cycle intermediates. These results provide new insight into the role of the in vivo activity of AOX in coordinating primary metabolism interactions that, partly, modulate the relative resistance of M. truncatula to diseases caused by soil-borne pathogenic fungi.
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Affiliation(s)
- Marwa Batnini
- Laboratory of Legumes, Center of Biotechnology of Borj Cedria, Hammamlif, Tunisia
- Faculty of Sciences of Tunis, University Tunis El Manar, Tunis, 2092, Tunisia
| | - Néstor Fernández Del-Saz
- Departamento de Botánica, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Concepción, Chile
| | - Mateu Fullana-Pericàs
- Grup de Recerca en Biologia de les Plantes en Condicions Mediterranies, Departament de Biologia, Universitat de les Illes Balears, Palma de Mallorca, 07122, Spain
| | - Francisco Palma
- Department of Plant Physiology, Faculty of sciences, University of Granada, Granada, 18071, Spain
| | - Imen Haddoudi
- Laboratory of Legumes, Center of Biotechnology of Borj Cedria, Hammamlif, Tunisia
- Faculty of Sciences of Tunis, University Tunis El Manar, Tunis, 2092, Tunisia
| | - Moncef Mrabet
- Laboratory of Legumes, Center of Biotechnology of Borj Cedria, Hammamlif, Tunisia
| | - Miquel Ribas-Carbo
- Departamento de Botánica, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Concepción, Chile
| | - Haythem Mhadhbi
- Laboratory of Legumes, Center of Biotechnology of Borj Cedria, Hammamlif, Tunisia
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10
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De Souza AP, Wang Y, Orr DJ, Carmo-Silva E, Long SP. Photosynthesis across African cassava germplasm is limited by Rubisco and mesophyll conductance at steady state, but by stomatal conductance in fluctuating light. THE NEW PHYTOLOGIST 2020; 225:2498-2512. [PMID: 31446639 PMCID: PMC7065220 DOI: 10.1111/nph.16142] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 08/15/2019] [Indexed: 05/18/2023]
Abstract
Sub-Saharan Africa is projected to see a 55% increase in food demand by 2035, where cassava (Manihot esculenta) is the most widely planted crop and a major calorie source. Yet, cassava yield in this region has not increased significantly for 13 yr. Improvement of genetic yield potential, the basis of the first Green Revolution, could be realized by improving photosynthetic efficiency. First, the factors limiting photosynthesis and their genetic variability within extant germplasm must be understood. Biochemical and diffusive limitations to leaf photosynthetic CO2 uptake under steady state and fluctuating light in 13 farm-preferred and high-yielding African cultivars were analyzed. A cassava leaf metabolic model was developed to quantify the value of overcoming limitations to leaf photosynthesis. At steady state, in vivo Rubisco activity and mesophyll conductance accounted for 84% of the limitation. Under nonsteady-state conditions of shade to sun transition, stomatal conductance was the major limitation, resulting in an estimated 13% and 5% losses in CO2 uptake and water use efficiency, across a diurnal period. Triose phosphate utilization, although sufficient to support observed rates, would limit improvement in leaf photosynthesis to 33%, unless improved itself. The variation of carbon assimilation among cultivars was three times greater under nonsteady state compared to steady state, pinpointing important overlooked breeding targets for improved photosynthetic efficiency in cassava.
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Affiliation(s)
- Amanda P. De Souza
- Carl R Woese Institute for Genomic Biology, University of
Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Yu Wang
- Carl R Woese Institute for Genomic Biology, University of
Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Douglas J. Orr
- Lancaster Environment Centre, Lancaster University,
Lancaster, LA1 4YQ, UK
| | | | - Stephen P. Long
- Carl R Woese Institute for Genomic Biology, University of
Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- Lancaster Environment Centre, Lancaster University,
Lancaster, LA1 4YQ, UK
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11
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Affiliation(s)
- David M Rosenthal
- Department of Environmental and Plant Biology, Ohio University, Athens, OH, 45701, USA
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12
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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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13
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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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14
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Sakoda K, Kaga A, Tanaka Y, Suzuki S, Fujii K, Ishimoto M, Shiraiwa T. Two novel quantitative trait loci affecting the variation in leaf photosynthetic capacity among soybeans. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2020; 291:110300. [PMID: 31928682 DOI: 10.1016/j.plantsci.2019.110300] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 10/01/2019] [Accepted: 10/03/2019] [Indexed: 05/13/2023]
Abstract
There is a large variation in CO2 assimilation rate per unit of leaf area (A) within or among crop species, which can be exploited to improve A by elucidating the mechanisms underlying such variation. The objective of the present study is to elucidate the genetic factors affecting the variation in leaf photosynthetic capacity among soybeans. Here, we conducted field experiments over three years, using Enrei, a leading variety in Japan, Peking, a landrace from China and the chromosome segment substitution lines derived from their progenies. The gas exchange measurements were conducted to evaluate A among soybean. Peking showed higher A than Enrei after the flowering in all the years. The genetic analysis identified two novel quantitative trait loci (QTLs) related to variation in A, which were located on chromosome 13 (qLPC13) and 20 (qLPC20). The Peking allele at qLPC13 increased A by 8.3 % in the Enrei genetic background, while the Peking allele at qLPC20 decreased A by 15.3 %. The present study is the first report on QTLs affecting a genotypic variation in leaf photosynthetic capacity among field-grown soybeans. The identification of the causal genes in these QTLs can provide a novel strategy to enhance leaf photosynthetic capacity with soybean breeding.
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Affiliation(s)
- Kazuma Sakoda
- Crop Science Laboratory, Graduate School of Agriculture, Kyoto University, Kyoto-city, Kyoto 606-8502, Japan; Research Fellow of Japan Society for the Promotion of Science, Japan.
| | - Akito Kaga
- Soybean and Field Crop Applied Genomics Research Unit, Institute of Crop Science, National Agriculture and Food Research Organization (NARO), Tsukuba-city, Ibaraki, Japan.
| | - Yu Tanaka
- Crop Science Laboratory, Graduate School of Agriculture, Kyoto University, Kyoto-city, Kyoto 606-8502, Japan; JST, PRESTO, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan.
| | - Seita Suzuki
- Crop Science Laboratory, Graduate School of Agriculture, Kyoto University, Kyoto-city, Kyoto 606-8502, Japan.
| | - Kenichiro Fujii
- Soybean and Field Crop Applied Genomics Research Unit, Institute of Crop Science, National Agriculture and Food Research Organization (NARO), Tsukuba-city, Ibaraki, Japan.
| | - Masao Ishimoto
- Division of Basic Research, Institute of Crop Science, National Agriculture and Food Research Organization (NARO), Tsukuba, Ibaraki 305-8518, Japan.
| | - Tatsuhiko Shiraiwa
- Crop Science Laboratory, Graduate School of Agriculture, Kyoto University, Kyoto-city, Kyoto 606-8502, Japan.
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15
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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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16
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Du Q, Liu T, Jiao X, Song X, Zhang J, Li J. Leaf anatomical adaptations have central roles in photosynthetic acclimation to humidity. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:4949-4962. [PMID: 31145790 DOI: 10.1093/jxb/erz238] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Accepted: 05/08/2019] [Indexed: 06/09/2023]
Abstract
Rates of photosynthesis can be lower in plants grown under conditions of high leaf-to-air vapour pressure difference (VPD) than under low VPD. Leaf phenotype plasticity is a primary factor determining photosynthetic responses to environmental stimuli. However, it remains unclear how changes in leaf anatomical traits drive photosynthetic acclimation to high VPD. Here, we examined the role of leaf anatomy in the differing photosynthetic responses of two tomato cultivars (Jinpeng and Zhongza) to long-term growth under high and low VPD. Photosynthesis was not affected by VPD in Jinpeng. This was attributed to homeostasis in stomatal conductance (gs) and, to a lesser extent, mesophyll conductance (gm). Disruption of synchronized changes to cell size in the epidermis and mesophyll meant that growth under high VPD reduced stomatal density in Jinpeng, but minor vein density remained unchanged. Thus, water supplied by the veins could support the increased transpirational demand, preventing stomatal closure. Variation in VPD did not affect mesophyll cell structures, and therefore gm, in Jinpeng. By contrast, photosynthesis in Zhongza was reduced under high VPD, which was primarily attributed to decreased gs and gm. The former was mainly induced by decreased stomatal aperture. Thus, transpirational demand exceeded water supply in Zhongza. This was likely due to coordinated decreases in stomatal and minor vein density driven by synchronized increases in epidermal and mesophyll cell size under high VPD. Liquid-phase limitation was primarily responsible for the reduced gm in Zhongza under high VPD. High VPD induced an increase in liquid-phase resistance by reducing the mesophyll surface area exposed to intercellular air spaces and increasing cytosolic resistance. These results suggest that plasticity in epidermal and mesophyll cell size provides an efficient means of regulating photosynthesis during acclimation to long-term high VPD.
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Affiliation(s)
- Qingjie Du
- College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China
| | - Tao Liu
- College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China
| | - Xiaocong Jiao
- College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China
| | - Xiaoming Song
- College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China
| | - Jiayu Zhang
- College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China
| | - Jianming Li
- College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China
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17
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Franco-Navarro JD, Rosales MA, Cubero-Font P, Calvo P, Álvarez R, Diaz-Espejo A, Colmenero-Flores JM. Chloride as a macronutrient increases water-use efficiency by anatomically driven reduced stomatal conductance and increased mesophyll diffusion to CO 2. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2019; 99:815-831. [PMID: 31148340 DOI: 10.1111/tpj.14423] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 05/17/2019] [Accepted: 05/22/2019] [Indexed: 05/27/2023]
Abstract
Chloride (Cl- ) has been recently described as a beneficial macronutrient, playing specific roles in promoting plant growth and water-use efficiency (WUE). However, it is still unclear how Cl- could be beneficial, especially in comparison with nitrate (NO3- ), an essential source of nitrogen that shares with Cl- similar physical and osmotic properties, as well as common transport mechanisms. In tobacco plants, macronutrient levels of Cl- specifically reduce stomatal conductance (gs ) without a concomitant reduction in the net photosynthesis rate (AN ). As stomata-mediated water loss through transpiration is inherent in the need of C3 plants to capture CO2 , simultaneous increase in photosynthesis and WUE is of great relevance to achieve a sustainable increase in C3 crop productivity. Our results showed that Cl- -mediated stimulation of larger leaf cells leads to a reduction in stomatal density, which in turn reduces gs and water consumption. Conversely, Cl- improves mesophyll diffusion conductance to CO2 (gm ) and photosynthetic performance due to a higher surface area of chloroplasts exposed to the intercellular airspace of mesophyll cells, possibly as a consequence of the stimulation of chloroplast biogenesis. A key finding of this study is the simultaneous improvement of AN and WUE due to macronutrient Cl- nutrition. This work identifies relevant and specific functions in which Cl- participates as a beneficial macronutrient for higher plants, uncovering a sustainable approach to improve crop yield.
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Affiliation(s)
- Juan D Franco-Navarro
- Instituto de Recursos Naturales y Agrobiología, CSIC, Avda Reina Mercedes 10, 41012, Sevilla, Spain
| | - Miguel A Rosales
- Instituto de Recursos Naturales y Agrobiología, CSIC, Avda Reina Mercedes 10, 41012, Sevilla, Spain
| | - Paloma Cubero-Font
- Instituto de Recursos Naturales y Agrobiología, CSIC, Avda Reina Mercedes 10, 41012, Sevilla, Spain
- Biochimie et Physiologie Moléculaire des Plantes (BPMP), Univ. Montpellier, CNRS, INRA, SupAgro, 2 Place P. Viala, Montpellier, 34060, France
| | - Purificación Calvo
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda Reina Mercedes 6, 41012, Sevilla, Spain
| | - Rosario Álvarez
- Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes 6, 41012, Sevilla, Spain
| | - Antonio Diaz-Espejo
- Instituto de Recursos Naturales y Agrobiología, CSIC, Avda Reina Mercedes 10, 41012, Sevilla, Spain
| | - José M Colmenero-Flores
- Instituto de Recursos Naturales y Agrobiología, CSIC, Avda Reina Mercedes 10, 41012, Sevilla, Spain
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18
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Bunce J. Consistent Differences in Field Leaf Water-Use Efficiency among Soybean Cultivars. PLANTS (BASEL, SWITZERLAND) 2019; 8:E123. [PMID: 31083277 PMCID: PMC6572017 DOI: 10.3390/plants8050123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 05/03/2019] [Accepted: 05/08/2019] [Indexed: 06/09/2023]
Abstract
High intrinsic water-use efficiency (WUEi), the ratio of leaf photosynthesis to stomatal conductance, may be a useful trait in adapting crops to water-limited environments. In soybean, cultivar differences in stomatal response to vapor pressure deficit have not consistently translated into differences in WUEi in the field. In this study, six cultivars of soybeans previously shown to differ in WUEi in indoor experiments were grown in the field in Beltsville, Maryland, and tested for mid-day WUEi on nine clear days during the mid-seasons of two years. Measurement dates were chosen for diverse temperatures, and air temperatures ranged from 21 to 34 °C on the different dates. Air saturation deficits for water vapor ranged from 0.9 to 2.2 kPa. Corrected carbon isotope delta values for 13C (CID) were determined on mature, upper canopy leaves harvested during early pod filling each year. WUEi differed among cultivars in both years and the differences were consistent across measurement dates. Correlations between mean WUEi and CID were not significant in either year. It is concluded that consistent cultivar differences in WUEi exist in these soybean cultivars under field conditions, but that carbon isotope ratios may not be useful in identifying them because of cultivar differences in mesophyll conductance.
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Affiliation(s)
- James Bunce
- USDA-ARS Adaptive Cropping Systems Lab (Retired), Beltsville, MD 20705, USA.
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19
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Leakey ADB, Ferguson JN, Pignon CP, Wu A, Jin Z, Hammer GL, Lobell DB. Water Use Efficiency as a Constraint and Target for Improving the Resilience and Productivity of C 3 and C 4 Crops. ANNUAL REVIEW OF PLANT BIOLOGY 2019; 70:781-808. [PMID: 31035829 DOI: 10.1146/annurev-arplant-042817-040305] [Citation(s) in RCA: 114] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The ratio of plant carbon gain to water use, known as water use efficiency (WUE), has long been recognized as a key constraint on crop production and an important target for crop improvement. WUE is a physiologically and genetically complex trait that can be defined at a range of scales. Many component traits directly influence WUE, including photosynthesis, stomatal and mesophyll conductances, and canopy structure. Interactions of carbon and water relations with diverse aspects of the environment and crop development also modulate WUE. As a consequence, enhancing WUE by breeding or biotechnology has proven challenging but not impossible. This review aims to synthesize new knowledge of WUE arising from advances in phenotyping, modeling, physiology, genetics, and molecular biology in the context of classical theoretical principles. In addition, we discuss how rising atmospheric CO2 concentration has created and will continue to create opportunities for enhancing WUE by modifying the trade-off between photosynthesis and transpiration.
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Affiliation(s)
- Andrew D B Leakey
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA;
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - John N Ferguson
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Charles P Pignon
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA;
| | - Alex Wu
- Centre for Crop Science and Centre of Excellence for Translational Photosynthesis, University of Queensland, St. Lucia, Queensland 4069, Australia
| | - Zhenong Jin
- Department of Earth System Science and Center for Food Security and Environment, Stanford University, Stanford, California 94305, USA
| | - Graeme L Hammer
- Centre for Crop Science and Centre of Excellence for Translational Photosynthesis, University of Queensland, St. Lucia, Queensland 4069, Australia
| | - David B Lobell
- Department of Earth System Science and Center for Food Security and Environment, Stanford University, Stanford, California 94305, USA
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20
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Du Y, Zhao Q, Li S, Yao X, Xie F, Zhao M. Shoot/Root Interactions Affect Soybean Photosynthetic Traits and Yield Formation: A Case Study of Grafting With Record-Yield Cultivars. FRONTIERS IN PLANT SCIENCE 2019; 10:445. [PMID: 31024606 PMCID: PMC6465614 DOI: 10.3389/fpls.2019.00445] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 03/25/2019] [Indexed: 05/29/2023]
Abstract
Improvement of soybean [Glycine max (L.) Merr.] yield and photosynthesis physiology have been achieved over decades of cultivar breeding. Identification of the mechanisms involved in shoot-root interactions would be beneficial for the development of yield improvement breeding strategies. The objectives of this study were to investigate soybean shoot-root interactions with different-year released soybean cultivars and to evaluate their effects on grain yield and yield components. Soybean grafts used in this study were constructed with two record-yield cultivars Liaodou14 (L14) and Zhonghuang35 (Z35) and eleven cultivars released in 1966-2006 from the United States and Chinese. The grafting experiments were conducted as pot-culture experiments and repeated in 2014 and 2015. Our results showed that net photosynthesis rate (P N) was positively correlated to both root activity and root bleeding sap mass (RBSM) during the R6 reproductive stage. Moreover, different year-released soybean shoots had all exhibited capabilities of changing the root activity and architecture of L14 and Z35 rootstocks to "generation"-specific patterns during all reproductive stages. However, these influences were independent of the photosynthetic strength. Yield analysis had demonstrated that high-yielding root systems (L14 and Z35 rootstocks) could cause more than 15% of yield increase in seven out of eleven common scions in a scion-genotype-dependent manner. For Williams-descendant cultivar scions, L14 and Z35 rootstocks promoted yields mainly by increasing the seed number (SN), but those scions of Amsoy-descendent cultivars showed mainly seed weight (SW) increases when grafted onto L14 and Z35 rootstocks. On the other hand, although most tested common rootstocks did not show significant influence over the final yields in record-yield L14 and Z35 scions, they were obviously capable of shifting the formation of yield components when compared to L14 and Z35 self-grafting controls. Taken together, soybean shoots could influence the root physiology and played a crucial role in the determination of yield potentials. Synergistically with shoots, soybean roots played a more supportive role during the realization of yield potentials through root activities and by balancing the formation of yield components. These findings provided interesting insightful information for developing new breeding strategies which aim to pyramid elite physiological and yield traits by selecting specific parental combinations.
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Affiliation(s)
- Yanli Du
- Soybean Research Institute, Shenyang Agricultural University, Shenyang, China
| | - Qiang Zhao
- Soybean Research Institute, Shenyang Agricultural University, Shenyang, China
| | - Shengyou Li
- Institute of Crop Research, Liaoning Academy of Agricultural Sciences, Shenyang, China
| | - Xingdong Yao
- Soybean Research Institute, Shenyang Agricultural University, Shenyang, China
| | - Futi Xie
- Soybean Research Institute, Shenyang Agricultural University, Shenyang, China
| | - Mingzhe Zhao
- Soybean Research Institute, Shenyang Agricultural University, Shenyang, China
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21
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Shrestha A, Buckley TN, Lockhart EL, Barbour MM. The response of mesophyll conductance to short- and long-term environmental conditions in chickpea genotypes. AOB PLANTS 2019; 11:ply073. [PMID: 30680087 PMCID: PMC6340285 DOI: 10.1093/aobpla/ply073] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2018] [Accepted: 12/07/2018] [Indexed: 05/23/2023]
Abstract
. Mesophyll conductance (g m) has been shown to vary between genotypes of a number of species and with growth environments, including nitrogen availability, but understanding of g m variability in legumes is limited. We might expect g m in legumes to respond differently to limited nitrogen availability, due to their ability to fix atmospheric N2. Using online stable carbon isotope discrimination method, we quantified genetic variability in g m under ideal conditions, investigated g m response to N source (N2-fixation or inorganic N) and determined the effects of N source and water availability on the rapid response of g m to photosynthetic photon flux density (PPFD) and radiation wavelength in three genotypes of chickpea (Cicer arietinum). Genotypes varied 2-fold in g m under non-limiting environments. N-fed plants had higher g m than N2-fixing plants in one genotype, while g m in the other two genotypes was unaffected. g m response to PPFD was altered by N source in one of three genotypes, in which the g m response to PPFD was statistically significant in N-fed plants but not in N2-fixing plants. There was no clear effect of moderate water stress on the g m response to PPFD and radiation wavelength. Genotypes of a single legume species differ in the sensitivity of g m to both long- and short-term environmental conditions, precluding utility in crop breeding programmes.
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Affiliation(s)
- Arjina Shrestha
- The Centre for Carbon, Water and Food, Faculty of Science, The University of Sydney, Sydney, Australia
| | - Thomas N Buckley
- The Centre for Carbon, Water and Food, Faculty of Science, The University of Sydney, Sydney, Australia
- Department of Plant Sciences, University of California, Davis, CA, USA
| | - Erin L Lockhart
- The Centre for Carbon, Water and Food, Faculty of Science, The University of Sydney, Sydney, Australia
| | - Margaret M Barbour
- The Centre for Carbon, Water and Food, Faculty of Science, The University of Sydney, Sydney, Australia
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22
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Tomeo NJ, Rosenthal DM. Photorespiration differs among Arabidopsis thaliana ecotypes and is correlated with photosynthesis. JOURNAL OF EXPERIMENTAL BOTANY 2018; 69:5191-5204. [PMID: 30053111 PMCID: PMC6184796 DOI: 10.1093/jxb/ery274] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 07/16/2018] [Indexed: 05/19/2023]
Abstract
A greater understanding of natural variation in photosynthesis will inform strategies for crop improvement by revealing overlooked opportunities. We use Arabidopsis thaliana ecotypes as a model system to assess (i) how photosynthesis and photorespiration covary and (ii) how mesophyll conductance influences water use efficiency (WUE). Phenotypic variation in photorespiratory CO2 efflux was correlated with assimilation rates and two metrics of photosynthetic capacity (i.e. VCmax and Jmax); however, genetic correlations were not detected between photosynthesis and photorespiration. We found standing genetic variation-as broad-sense heritability-for most photosynthetic traits, including photorespiration. Genetic correlation between photosynthetic electron transport and carboxylation capacities indicates that these traits are genetically constrained. Winter ecotypes had greater mesophyll conductance, maximum carboxylation capacity, maximum electron transport capacity, and leaf structural robustness when compared with spring ecotypes. Stomatal conductance varied little in winter ecotypes, leading to a positive correlation between integrated WUE and mesophyll conductance. Thus, variation in mesophyll conductance can modulate WUE among A. thaliana ecotypes without a significant loss in assimilation. Genetic correlations between traits supplying energy and carbon to the Calvin-Benson cycle are consistent with biochemical models, suggesting that selection on either of these traits would improve all of them. Similarly, the lack of a genetic correlation between photosynthesis and photorespiration suggests that the positive scaling of these two traits can be broken.
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Affiliation(s)
- Nicholas J Tomeo
- Ohio University, Department of Environmental and Plant Biology, Athens, OH, USA
| | - David M Rosenthal
- Ohio University, Department of Environmental and Plant Biology, Athens, OH, USA
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Sinclair TR. Effective Water Use Required for Improving Crop Growth Rather Than Transpiration Efficiency. FRONTIERS IN PLANT SCIENCE 2018; 9:1442. [PMID: 30323828 PMCID: PMC6172333 DOI: 10.3389/fpls.2018.01442] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Accepted: 09/11/2018] [Indexed: 05/08/2023]
Abstract
The phenomenological expression showing crop yield to be directly dependent on crop transpiration use efficiency (TE) has encouraged continued focus on TE as a viable approach to increasing crop yields. The difficulty in the phenomenological perspective is that research tends not to match up with the underlying mechanistic variables defining TE. Experimental evidence and the mechanistic derivation of TE by Tanner and Sinclair showed that the common focus on increasing the intrinsic ratio of leaf CO2/H2O exchange has limited opportunities for improvement. On the other hand, the derivation showed that daily vapor pressure deficit (VPD) weighted for the daily cycle of transpiration rate has a large, direct impact on TE. While VPD is often viewed as an environmental variable, daily weighted VPD can be under plant control as a result of partial stomatal closure during the midday. A critical feature of the partial stomatal closure is that transpiration rate is decreased resulting in conservation of soil water. The conserved soil water allows late-season, sustained physiological activity during subsequent periods of developing water deficits, which can be especially beneficial during reproductive development. The shift in the temporal dynamics of water use by water conservations traits has been shown in simulation studies to result in substantial yield increases. It is suggested from this analysis that effective water use through the growing season is more important for increasing crop yield than attempts focused on improving the static, intrinsic TE ratio.
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Affiliation(s)
- Thomas R. Sinclair
- Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC, United States
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Dwivedi SL, Siddique KHM, Farooq M, Thornton PK, Ortiz R. Using Biotechnology-Led Approaches to Uplift Cereal and Food Legume Yields in Dryland Environments. FRONTIERS IN PLANT SCIENCE 2018; 9:1249. [PMID: 30210519 PMCID: PMC6120061 DOI: 10.3389/fpls.2018.01249] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 08/06/2018] [Indexed: 05/29/2023]
Abstract
Drought and heat in dryland agriculture challenge the enhancement of crop productivity and threaten global food security. This review is centered on harnessing genetic variation through biotechnology-led approaches to select for increased productivity and stress tolerance that will enhance crop adaptation in dryland environments. Peer-reviewed literature, mostly from the last decade and involving experiments with at least two seasons' data, form the basis of this review. It begins by highlighting the adverse impact of the increasing intensity and duration of drought and heat stress due to global warming on crop productivity and its impact on food and nutritional security in dryland environments. This is followed by (1) an overview of the physiological and molecular basis of plant adaptation to elevated CO2 (eCO2), drought, and heat stress; (2) the critical role of high-throughput phenotyping platforms to study phenomes and genomes to increase breeding efficiency; (3) opportunities to enhance stress tolerance and productivity in food crops (cereals and grain legumes) by deploying biotechnology-led approaches [pyramiding quantitative trait loci (QTL), genomic selection, marker-assisted recurrent selection, epigenetic variation, genome editing, and transgene) and inducing flowering independent of environmental clues to match the length of growing season; (4) opportunities to increase productivity in C3 crops by harnessing novel variations (genes and network) in crops' (C3, C4) germplasm pools associated with increased photosynthesis; and (5) the adoption, impact, risk assessment, and enabling policy environments to scale up the adoption of seed-technology to enhance food and nutritional security. This synthesis of technological innovations and insights in seed-based technology offers crop genetic enhancers further opportunities to increase crop productivity in dryland environments.
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Affiliation(s)
| | | | - Muhammad Farooq
- The UWA Institute of Agriculture, The University of Western Australia, Perth, WA, Australia
- Department of Crop Sciences, College of Agricultural and Marine Sciences, Sultan Qaboos University, Al Khoud, Oman
- University of Agriculture, Faisalabad, Pakistan
| | - Philip K. Thornton
- CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS), International Livestock Research Institute (ILRI), Nairobi, Kenya
| | - Rodomiro Ortiz
- Department of Plant Breeding, Swedish University of Agricultural Sciences, Alnarp, Sweden
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Divergent drivers of leaf trait variation within species, among species, and among functional groups. Proc Natl Acad Sci U S A 2018; 115:5480-5485. [PMID: 29724857 PMCID: PMC6003520 DOI: 10.1073/pnas.1803989115] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Understanding variation in leaf functional traits-including rates of photosynthesis and respiration and concentrations of nitrogen and phosphorus-is a fundamental challenge in plant ecophysiology. When expressed per unit leaf area, these traits typically increase with leaf mass per area (LMA) within species but are roughly independent of LMA across the global flora. LMA is determined by mass components with different biological functions, including photosynthetic mass that largely determines metabolic rates and contains most nitrogen and phosphorus, and structural mass that affects toughness and leaf lifespan (LL). A possible explanation for the contrasting trait relationships is that most LMA variation within species is associated with variation in photosynthetic mass, whereas most LMA variation across the global flora is associated with variation in structural mass. This hypothesis leads to the predictions that (i) gas exchange rates and nutrient concentrations per unit leaf area should increase strongly with LMA across species assemblages with low LL variance but should increase weakly with LMA across species assemblages with high LL variance and that (ii) controlling for LL variation should increase the strength of the above LMA relationships. We present analyses of intra- and interspecific trait variation from three tropical forest sites and interspecific analyses within functional groups in a global dataset that are consistent with the above predictions. Our analysis suggests that the qualitatively different trait relationships exhibited by different leaf assemblages can be understood by considering the degree to which photosynthetic and structural mass components contribute to LMA variation in a given assemblage.
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Blessing CH, Mariette A, Kaloki P, Bramley H. Profligate and conservative: water use strategies in grain legumes. JOURNAL OF EXPERIMENTAL BOTANY 2018; 69:349-369. [PMID: 29370385 DOI: 10.1093/jxb/erx415] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2017] [Accepted: 10/23/2017] [Indexed: 06/07/2023]
Abstract
Yields of grain legumes are constrained by available water. Thus, it is crucial to understand traits influencing water uptake and the efficiency of using water to produce biomass. Global comparisons and comparisons at specific locations reveal that water use of different grain legumes is very similar, which indicates that water use efficiency varies over a wide range due to differences in biomass and yield. Moreover, yield increases more per millimetre of water used in cool season grain legumes than warm season species. Although greater contrasts have been observed across species and genotypes at the pot and lysimeter level, agronomic factors need to be taken into account when scaling those studies to field-level responses. Conservative water use strategies in grain legumes such as low stomatal conductance as approximated by low photosynthetic carbon isotope discrimination reduces yield potential, whereas temporal adjustments of stomatal conductance within the growing season and in response to environmental factors (such as vapour pressure deficit) helps to optimize the trade-off between carbon gain and water loss. Furthermore, improved photosynthetic capacity, reduced mesophyll conductance, reduced boundary layer, and re-fixation of respired CO2 were identified as traits that are beneficial without water deficit, but also under terminal and transient drought. Genotypic variability in some grain legume species has been observed for several traits that influence water use, water use efficiency, and yield, including root length and the temporal pattern of water use, but even more variation is expected from wild relatives. Albeit that N2 fixation decreases under drought, its impact on water use is still largely unknown, but the nitrogen source influences gas exchange and, thus, transpiration efficiency. This review concludes that conservative traits are needed under conditions of terminal drought to help maintain soil moisture until the pod-filling period, but profligate traits, if tightly regulated, are important under conditions of transient drought in order to profit from short intermittent periods of available soil moisture.
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Affiliation(s)
- Carola H Blessing
- The University of Sydney, School of Life and Environmental Sciences, Sydney Institute of Agriculture, Sydney, New South Wales, Australia
| | - Alban Mariette
- The University of Sydney, Plant Breeding Institute, Narrabri, New South Wales, Australia
- Biology Department, Université de Rennes 1, Campus de Beaulieu, Rennes Cedex, France
| | - Peter Kaloki
- The University of Sydney, School of Life and Environmental Sciences, Sydney Institute of Agriculture, Sydney, New South Wales, Australia
- The University of Sydney, Plant Breeding Institute, Narrabri, New South Wales, Australia
| | - Helen Bramley
- The University of Sydney, School of Life and Environmental Sciences, Sydney Institute of Agriculture, Sydney, New South Wales, Australia
- The University of Sydney, Plant Breeding Institute, Narrabri, New South Wales, Australia
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27
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van der Putten PEL, Yin X, Struik PC. Calibration matters: On the procedure of using the chlorophyll fluorescence method to estimate mesophyll conductance. JOURNAL OF PLANT PHYSIOLOGY 2018; 220:167-172. [PMID: 29190520 DOI: 10.1016/j.jplph.2017.11.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 11/17/2017] [Accepted: 11/20/2017] [Indexed: 06/07/2023]
Abstract
Estimates of mesophyll conductance (gm), when calculated from chlorophyll fluorescence, are uncertain, especially when the photosystem II (PSII) operating efficiency is measured from the traditional single saturation pulse methodology. The multiphase flash method has recently been recommended to replace the single saturation pulse method, allowing a more reliable estimation of gm. Also, many researchers still directly use the PSII operating efficiency to derive linear electron transport rate J (that is required to estimate gm), without appropriate calibration using measurements under non-photorespiratory conditions. Here we demonstrate for tomato and rice that (i) using the multiphase flash method did not yield realistic estimates of gm if no calibration was conducted; and (ii) using the single saturation pulse method still gave reasonable estimates of gm when calibration based on the non-photorespiratory measurements was properly conducted. Therefore, conducting calibration based on data under non-photorespiratory conditions was indispensable for a reliable estimation of gm, regardless whether the multiphase flash or the single saturation pulse method was used for measuring the PSII operating efficiency. Other issues related to the procedure of using the chlorophyll fluorescence method to estimate gm were discussed.
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Affiliation(s)
- Peter E L van der Putten
- Centre for Crop Systems Analysis, Department of Plant Sciences, Wageningen University & Research, P.O. Box 430, 6700 AK, Wageningen, The Netherlands
| | - Xinyou Yin
- Centre for Crop Systems Analysis, Department of Plant Sciences, Wageningen University & Research, P.O. Box 430, 6700 AK, Wageningen, The Netherlands.
| | - Paul C Struik
- Centre for Crop Systems Analysis, Department of Plant Sciences, Wageningen University & Research, P.O. Box 430, 6700 AK, Wageningen, The Netherlands
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28
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Evans JR, Morgan PB, von Caemmerer S. Light Quality Affects Chloroplast Electron Transport Rates Estimated from Chl Fluorescence Measurements. PLANT & CELL PHYSIOLOGY 2017; 58:1652-1660. [PMID: 29016964 DOI: 10.1093/pcp/pcx103] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 07/09/2017] [Indexed: 05/23/2023]
Abstract
Chl fluorescence has been used widely to calculate photosynthetic electron transport rates. Portable photosynthesis instruments allow for combined measurements of gas exchange and Chl fluorescence. We analyzed the influence of spectral quality of actinic light on Chl fluorescence and the calculated electron transport rate, and compared this with photosynthetic rates measured by gas exchange in the absence of photorespiration. In blue actinic light, the electron transport rate calculated from Chl fluorescence overestimated the true rate by nearly a factor of two, whereas there was closer agreement under red light. This was consistent with the prediction made with a multilayer leaf model using profiles of light absorption and photosynthetic capacity. Caution is needed when interpreting combined measurements of Chl fluorescence and gas exchange, such as the calculation of CO2 partial pressure in leaf chloroplasts.
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Affiliation(s)
- John R Evans
- 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
| | - Patrick B Morgan
- LI-COR Inc., Lincoln, NE 68504, USA
- School of Natural Resources, University of Nebraska-Lincoln, Lincoln, NE 68504, USA
| | - 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
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