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Jia J, Jiang H, Zhu X, Wang S, Wang L, Liu C, Li W, Huang W. Inorganic carbon utilization strategies of plateau aquatic plants in response to native habitats. PHOTOSYNTHESIS RESEARCH 2024; 162:47-62. [PMID: 39133367 DOI: 10.1007/s11120-024-01115-4] [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: 05/29/2024] [Accepted: 07/29/2024] [Indexed: 08/13/2024]
Abstract
Aquatic plants are a crucial component of the aquatic ecosystem in the Tibetan Plateau region. Researching the adaptability of plateau aquatic plants in photosynthesis to the plateau environment can enhance understanding of the operational mechanisms of plateau ecosystems, thereby providing a scientific basis for the protection and management of plateau aquatic ecosystems. This study presents an investigation of photosynthetic inorganic carbon utilization strategies and photosynthetic efficiency of 17 aquatic plants under natural growing conditions in Niyang River basin on the Tibetan Plateau. In pH-drift experiments, 10 of 17 species were able to utilize HCO3-, and environmental factors like water pH were shown to have a significant effect on the ability of the tested species to utilize HCO3-. Titratable acidity in the leaves of Stuckenia filiformis, Zannichellia palustris, Batrachium bungei, and Myriophyllum spicatum showed significant diurnal fluctuations at certain sampling sites, indicating the presence of CAM. In B. bungei, water pH positively correlated with CAM activity, while CO2 concentration negatively correlated with CAM activity. The chlorophyll fluorescence analysis revealed that aquatic plants inhabiting the Tibetan Plateau exhibited photosynthetic adaptations. In conclusion, the aquatic plants on the Tibetan Plateau employ diverse strategies for utilizing inorganic carbon during photosynthesis, exhibiting their flexible adaptability to the native high-altitude habitats of the Tibetan Plateau.
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Affiliation(s)
- Jiajia Jia
- Key Laboratory of Biodiversity and Environment on the Qinghai-Tibetan Plateau, Ministry of Education, School of Ecology and Environment, Tibet University, Lhasa, 850000, China
- Aquatic Plant Research Center, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
| | - Hongsheng Jiang
- Aquatic Plant Research Center, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Hubei Key Laboratory of Wetland Evolution & Ecological Restoration, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
| | - Xi Zhu
- Aquatic Plant Research Center, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Life Sciences, Hainan University, HaiKou, 570228, China
| | - Shanwei Wang
- Aquatic Plant Research Center, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- School of Environmental Studies, China University of Geosciences, Wuhan, 430074, China
| | - Liyuan Wang
- Aquatic Plant Research Center, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
| | | | - Wei Li
- Key Laboratory of Biodiversity and Environment on the Qinghai-Tibetan Plateau, Ministry of Education, School of Ecology and Environment, Tibet University, Lhasa, 850000, China.
- Aquatic Plant Research Center, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China.
- Hubei Key Laboratory of Wetland Evolution & Ecological Restoration, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China.
- Yani Wetland Ecosystem Positioning Observation and Research Station, Tibet University, Lhasa, China.
| | - Wenmin Huang
- Aquatic Plant Research Center, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China.
- Hubei Key Laboratory of Wetland Evolution & Ecological Restoration, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China.
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Horiguchi G, Matsumoto K, Nemoto K, Inokuchi M, Hirotsu N. Transition From Proto-Kranz-Type Photosynthesis to HCO 3 - Use Photosynthesis in the Amphibious Plant Hygrophila polysperma. FRONTIERS IN PLANT SCIENCE 2021; 12:675507. [PMID: 34220895 PMCID: PMC8242947 DOI: 10.3389/fpls.2021.675507] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 04/26/2021] [Indexed: 06/13/2023]
Abstract
Hygrophila polysperma is a heterophyllous amphibious plant. The growth of H. polysperma in submerged conditions is challenging due to the low CO2 environment, increased resistance to gas diffusion, and bicarbonate ion (HCO3 -) being the dominant dissolved inorganic carbon source. The submerged leaves of H. polysperma have significantly higher rates of underwater photosynthesis compared with the terrestrial leaves. 4,4'-Diisothiocyanatostilbene-2,2'-disulfonate (DIDS), an anion exchanger protein inhibitor, and ethoxyzolamide (EZ), an inhibitor of internal carbonic anhydrase, repressed underwater photosynthesis by the submerged leaves. These results suggested that H. polysperma acclimates to the submerged condition by using HCO3 - for photosynthesis. H. polysperma transports HCO3 - into the leaf by a DIDS-sensitive HCO3 - transporter and converted to CO2 by carbonic anhydrase. Additionally, proteome analysis revealed that submerged leaves accumulated fewer proteins associated with C4 photosynthesis compared with terrestrial leaves. This finding suggested that H. polysperma is capable of C4 and C3 photosynthesis in the terrestrial and submerged leaves, respectively. The ratio of phosphoenol pyruvate carboxylase to ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) in the submerged leaves was less than that in the terrestrial leaves. Upon anatomical observation, the terrestrial leaves exhibited a phenotype similar to the Kranz anatomy found among C4 plants; however, chloroplasts in the bundle sheath cells were not located adjacent to the vascular bundles, and the typical Kranz anatomy was absent in submerged leaves. These results suggest that H. polysperma performs proto-Kranz type photosynthesis in a terrestrial environment and shifts from a proto-Kranz type in terrestrial leaves to a HCO3 - use photosynthesis in the submerged environments.
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Affiliation(s)
- Genki Horiguchi
- Graduate School of Life Sciences, Toyo University, Gunma, Japan
| | | | - Kyosuke Nemoto
- Graduate School of Life Sciences, Toyo University, Gunma, Japan
| | - Mayu Inokuchi
- Faculty of Life Sciences, Toyo University, Gunma, Japan
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Naoki Hirotsu
- Graduate School of Life Sciences, Toyo University, Gunma, Japan
- Faculty of Life Sciences, Toyo University, Gunma, Japan
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Huang W, Han S, Xing Z, Li W. Responses of Leaf Anatomy and CO 2 Concentrating Mechanisms of the Aquatic Plant Ottelia cordata to Variable CO 2. FRONTIERS IN PLANT SCIENCE 2020; 11:1261. [PMID: 32922428 PMCID: PMC7457065 DOI: 10.3389/fpls.2020.01261] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 07/31/2020] [Indexed: 06/11/2023]
Abstract
Acclimation to variable CO2 was studied in floating leaves of the freshwater monocot Ottelia cordata grown in either low or high CO2. The most striking anatomical variations responding to high CO2 included the enlarged upper epidermal cells and the decreased area of epidermal chloroplasts. Stomata that distributed on the upper surface, and the stomatic chamber area, showed no significant response to high CO2. pH-drift experiments indicated that floating leaves of O. cordata were able to use bicarbonate regardless of CO2 concentrations. Photosynthetic enzyme activities and patterns of organic acids fluctuation confirmed that floating leaves of O. cordata can operate CAM only at low CO2, and perform C4-like metabolism at both high and low CO2. Overall, the present results imply that the floating leaves of O. cordata does not just rely on the atmospheric CO2 for its inorganic carbon, but is also dependent on CO2 and bicarbonate in the water. By showing these effects of CO2 variation, we highlight the need for further experimental studies on the regulatory mechanisms in O. cordata floating leaves, that prevent futile cycling among the three CO2 concentrating mechanisms (bicarbonate use, C4, and CAM metabolism) and the strategy for exploiting atmospheric CO2, as well as studies on the detailed biochemical pathway for C4 and CAM metabolism in this species.
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Affiliation(s)
- Wenmin Huang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Center of Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, China
- Aix Marseille Univ CNRS, BIP UMR 7281, IMM, FR 3479, Marseille, France
| | - Shijuan Han
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Center of Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Zhenfei Xing
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China
| | - Wei Li
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Center of Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, China
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Han S, Maberly SC, Gontero B, Xing Z, Li W, Jiang H, Huang W. Structural basis for C4 photosynthesis without Kranz anatomy in leaves of the submerged freshwater plant Ottelia alismoides. ANNALS OF BOTANY 2020; 125:869-879. [PMID: 31942934 PMCID: PMC7218808 DOI: 10.1093/aob/mcaa005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 01/14/2020] [Indexed: 06/10/2023]
Abstract
BACKGROUND AND AIMS Ottelia alismoides (Hydrocharitaceae) is a freshwater macrophyte that, unusually, possesses three different CO2-concentrating mechanisms. Here we describe its leaf anatomy and chloroplast ultrastructure, how these are altered by CO2 concentration and how they may underlie C4 photosynthesis. METHODS Light and transmission electron microscopy were used to study the anatomy of mature leaves of O. alismoides grown at high and low CO2 concentrations. Diel acid change and the activity of phosphoenolpyruvate carboxylase were measured to confirm that CAM activity and C4 photosynthesis were present. KEY RESULTS When O. alismoides was grown at low CO2, the leaves performed both C4 and CAM photosynthesis whereas at high CO2 leaves used C4 photosynthesis. The leaf comprised an upper and lower layer of epidermal cells separated by a large air space occupying about 22 % of the leaf transverse-section area, and by mesophyll cells connecting the two epidermal layers. Kranz anatomy was absent. At low CO2, chloroplasts in the mesophyll cells were filled with starch even at the start of the photoperiod, while epidermal chloroplasts contained small starch grains. The number of chloroplasts in the epidermis was greater than in the mesophyll cells. At high CO2, the structure was unchanged but the thicknesses of the two epidermal layers, the air space, mesophyll and the transverse-section area of cells and air space were greater. CONCLUSIONS Leaves of O. alismoides have epidermal and mesophyll cells that contain chloroplasts and large air spaces but lack Kranz anatomy. The high starch content of mesophyll cells suggests they may benefit from an internal source of CO2, for example via C4 metabolism, and are also sites of starch storage. The air spaces may help in the recycling of decarboxylated or respired CO2. The structural similarity of leaves at low and high CO2 is consistent with the constitutive nature of bicarbonate and C4 photosynthesis. There is sufficient structural diversity within the leaf of O. alismoides to support dual-cell C4 photosynthesis even though Kranz anatomy is absent.
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Affiliation(s)
- Shijuan Han
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Stephen C Maberly
- Lake Ecosystems Group, UK Centre for Ecology & Hydrology, Lancaster Environment Centre, Bailrigg, Lancaster, UK
| | - Brigitte Gontero
- Aix Marseille Univ CNRS, BIP UMR, IMM, FR, Chemin Joseph Aiguier, Marseille Cedex, France
| | - Zhenfei Xing
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China
| | - Wei Li
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
- Center for Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, China
| | - Hongsheng Jiang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
| | - Wenmin Huang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
- Aix Marseille Univ CNRS, BIP UMR, IMM, FR, Chemin Joseph Aiguier, Marseille Cedex, France
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Horiguchi G, Nemoto K, Yokoyama T, Hirotsu N. Photosynthetic acclimation of terrestrial and submerged leaves in the amphibious plant Hygrophila difformis. AOB PLANTS 2019; 11:plz009. [PMID: 30911367 PMCID: PMC6426153 DOI: 10.1093/aobpla/plz009] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2018] [Revised: 01/17/2019] [Accepted: 02/25/2019] [Indexed: 05/07/2023]
Abstract
Hygrophila difformis, a heterophyllous amphibious plant, develops serrated or dissected leaves when grown in terrestrial or submerged conditions, respectively. In this study, we tested whether submerged leaves and ethylene-induced leaves of the heterophyllous, amphibious plant H. difformis have improved photosynthetic ability under submerged conditions. Also, we investigated how this amphibious plant photosynthesizes underwater and whether a HCO3 - transport system is present. We have analysed leaf morphology, measured underwater photosynthetic rates and HCO3 - affinity in H. difformis to determine if there are differences in acclimation ability dependent on growth conditions: terrestrial, submerged, terrestrial treated with ethylene and submerged treated with an ethylene inhibitor. Moreover, we measured time courses for changes in leaf anatomical characteristics and underwater photosynthesis in terrestrial leaves after submersion. Compared with the leaves of terrestrially grown plants, leaf thickness of submerged plants was significantly thinner. The stomatal density on the abaxial surface of submerged leaves was also reduced, and submerged plants had a significantly higher O2 evolution rate. When the leaves of terrestrially grown plants were treated with ethylene, their leaf morphology and underwater photosynthesis increased to levels comparable to those of submerged leaves. Underwater photosynthesis of terrestrial leaves was significantly higher by 5 days after submersion. In contrast, leaf morphology did not change after submergence. Submerged leaves and submerged terrestrial leaves were able to use bicarbonate but submerged terrestrial leaves had an intermediate ability to use HCO3 - that was between terrestrial leaves and submerged leaves. Ethoxyzolamide, an inhibitor of intracellular carbonic anhydrase, significantly inhibited underwater photosynthesis in submerged leaves. This amphibious plant acclimates to the submerged condition by changing leaf morphology and inducing a HCO3 - utilizing system, two processes that are regulated by ethylene.
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Affiliation(s)
- Genki Horiguchi
- Graduate School of Life Sciences, Toyo University, Itakura-machi, Oura-gun, Gunma, Japan
| | - Kyosuke Nemoto
- Graduate School of Life Sciences, Toyo University, Itakura-machi, Oura-gun, Gunma, Japan
| | - Tomomi Yokoyama
- Faculty of Life Sciences, Toyo University, Itakura-machi, Oura-gun, Gunma, Japan
| | - Naoki Hirotsu
- Graduate School of Life Sciences, Toyo University, Itakura-machi, Oura-gun, Gunma, Japan
- Faculty of Life Sciences, Toyo University, Itakura-machi, Oura-gun, Gunma, Japan
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Huang WM, Shao H, Zhou SN, Zhou Q, Fu WL, Zhang T, Jiang HS, Li W, Gontero B, Maberly SC. Different CO 2 acclimation strategies in juvenile and mature leaves of Ottelia alismoides. PHOTOSYNTHESIS RESEARCH 2018; 138:219-232. [PMID: 30078074 DOI: 10.1007/s11120-018-0568-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 07/28/2018] [Indexed: 06/08/2023]
Abstract
The freshwater macrophyte, Ottelia alismoides, is a bicarbonate user performing C4 photosynthesis in the light, and crassulacean acid metabolism (CAM) when acclimated to low CO2. The regulation of the three mechanisms by CO2 concentration was studied in juvenile and mature leaves. For mature leaves, the ratios of phosphoenolpyruvate carboxylase (PEPC) to ribulose-bisphosphate carboxylase/oxygenase (Rubisco) are in the range of that of C4 plants regardless of CO2 concentration (1.5-2.5 at low CO2, 1.8-3.4 at high CO2). In contrast, results for juvenile leaves suggest that C4 is facultative and only present under low CO2. pH-drift experiments showed that both juvenile and mature leaves can use bicarbonate irrespective of CO2 concentration, but mature leaves have a significantly greater carbon-extracting ability than juvenile leaves at low CO2. At high CO2, neither juvenile nor mature leaves perform CAM as indicated by lack of diurnal acid fluctuation. However, CAM was present at low CO2, though the fluctuation of titratable acidity in juvenile leaves (15-17 µequiv g-1 FW) was slightly but significantly lower than in mature leaves (19-25 µequiv g-1 FW), implying that the capacity to perform CAM increases as leaves mature. The increased CAM activity is associated with elevated PEPC activity and large diel changes in starch content. These results show that in O. alismoides, carbon-dioxide concentrating mechanisms are more effective in mature compared to juvenile leaves, and C4 is facultative in juvenile leaves but constitutive in mature leaves.
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Affiliation(s)
- Wen Min Huang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Hubei Key Laboratory of Wetland Evolution & Ecological Restoration, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
| | - Hui Shao
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Aix Marseille Univ, CNRS, BIP, UMR 7281, 31 Chemin Joseph Aiguier, CS70071, 13402, Marseille Cedex 09, France
| | - Si Ning Zhou
- Sino-Danish Center, The University of Chinese Academy of Sciences, Beijing, 101400, China
| | - Qin Zhou
- School of Resources and Environmental Science, Hubei University, Wuhan, 430074, China
| | - Wen Long Fu
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
| | - Ting Zhang
- School of Resource and Environmental Engineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Hong Sheng Jiang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Hubei Key Laboratory of Wetland Evolution & Ecological Restoration, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
| | - Wei Li
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Hubei Key Laboratory of Wetland Evolution & Ecological Restoration, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
| | - Brigitte Gontero
- Aix Marseille Univ, CNRS, BIP, UMR 7281, 31 Chemin Joseph Aiguier, CS70071, 13402, Marseille Cedex 09, France.
| | - Stephen C Maberly
- Lake Ecosystems Group, Centre for Ecology & Hydrology, Lancaster Environment Centre, Library Avenue, Lancaster, Bailrigg, LA1 4AP, UK.
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Trade-offs and Synergies in the Structural and Functional Characteristics of Leaves Photosynthesizing in Aquatic Environments. ACTA ACUST UNITED AC 2018. [DOI: 10.1007/978-3-319-93594-2_11] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
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Pedersen O, Colmer TD, Garcia-Robledo E, Revsbech NP. CO2 and O2 dynamics in leaves of aquatic plants with C3 or CAM photosynthesis - application of a novel CO2 microsensor. ANNALS OF BOTANY 2018; 122:605-615. [PMID: 29893789 PMCID: PMC6153474 DOI: 10.1093/aob/mcy095] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 05/07/2018] [Indexed: 05/29/2023]
Abstract
Background and Aims Leaf tissue CO2 partial pressure (pCO2) shows contrasting dynamics over a diurnal cycle in C3 and Crassulacean Acid Metabolism (CAM) plants. However, simultaneous and continuous monitoring of pCO2 and pO2 in C3 and CAM plants under the same conditions was lacking. Our aim was to use a new CO2 microsensor and an existing O2 microsensor for non-destructive measurements of leaf pCO2 and pO2 dynamics to compare a C3 and a CAM plant in an aquatic environment. Methods A new amperometric CO2 microsensor and an O2 microsensor elucidated with high temporal resolution the dynamics in leaf pCO2 and pO2 during light-dark cycles for C3Lobelia dortmanna and CAM Littorella uniflora aquatic plants. Underwater photosynthesis, dark respiration, tissue malate concentrations and sediment CO2 and O2 were also measured. Key Results During the dark period, for the C3 plant, pCO2 increased to approx. 3.5 kPa, whereas for the CAM plant CO2 was mostly below 0.05 kPa owing to CO2 sequestration into malate. Upon darkness, the CAM plant had an initial peak in pCO2 (approx. 0.16 kPa) which then declined to a quasi-steady state for several hours and then pCO2 increased towards the end of the dark period. The C3 plant became severely hypoxic late in the dark period, whereas the CAM plant with greater cuticle permeability did not. Upon illumination, leaf pCO2 declined and pO2 increased, although aspects of these dynamics also differed between the two plants. Conclusions The continuous measurements of pCO2 and pO2 highlighted the contrasting tissue gas compositions in submerged C3 and CAM plants. The CAM leaf pCO2 dynamics indicate an initial lag in CO2 sequestration to malate, which after several hours of malate synthesis then slows. Like the use of O2 microsensors to resolve questions related to plant aeration, deployment of the new CO2 microsensor will benefit plant ecophysiology research.
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Affiliation(s)
- Ole Pedersen
- Freshwater Biological Laboratory, Department of Biology, University of Copenhagen, Copenhagen, Denmark
- UWA School of Agriculture and Environment, Faculty of Science, The University of Western Australia, Crawley, WA, Australia
| | - Timothy D Colmer
- UWA School of Agriculture and Environment, Faculty of Science, The University of Western Australia, Crawley, WA, Australia
| | - Emilio Garcia-Robledo
- Microbiology, Department of Bioscience, Aarhus University, Aarhus C, Denmark
- Ecology, Department of Biology, University of Cadiz, Poligono Rio San Pedro, Puerto Real, Cadiz, Spain
| | - Niels P Revsbech
- Microbiology, Department of Bioscience, Aarhus University, Aarhus C, Denmark
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Konnerup D, Pedersen O. Flood tolerance of Glyceria fluitans: the importance of cuticle hydrophobicity, permeability and leaf gas films for underwater gas exchange. ANNALS OF BOTANY 2017; 120:521-528. [PMID: 29059317 PMCID: PMC5737359 DOI: 10.1093/aob/mcx083] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Revised: 05/03/2017] [Accepted: 06/02/2017] [Indexed: 06/07/2023]
Abstract
Background and Aims Floating sweet-grass ( Glyceria fluitans ) can form aerial as well as floating leaves, and these both possess superhydrophobic cuticles, so that gas films are retained when submerged. However, only the adaxial side of the floating leaves is superhydrophobic, so the abaxial side is directly in contact with the water. The aim of this study was to assess the effect of these different gas films on underwater net photosynthesis ( P N ) and dark respiration ( R D ). Methods Evolution of O 2 was used to measure underwater P N in relation to dissolved CO 2 on leaf segments with or without gas films, and O 2 microelectrodes were used to assess cuticle resistance of floating leaves to O 2 uptake in the dark. Key Results The adaxial side of aerial leaves was more hydrophobic than the abaxial side and also initially retained a thicker gas film when submerged. Underwater P N vs. dissolved CO 2 of aerial leaf segments with gas films had a K m of 172 mmol CO 2 m -3 and a P max of 7·1 μmol O 2 m -2 s -1 , and the leaf gas films reduced the apparent resistance to CO 2 uptake 12-fold. Underwater P N of floating leaves measured at 700 mmol CO 2 m -3 was 1·5-fold higher than P N of aerial leaves. The floating leaves had significantly lower cuticle resistance to dark O 2 uptake on the wettable abaxial side compared with the superhydrophobic adaxial side. Conclusions Glyceria fluitans showed high rates of underwater P N and these were obtained at environmentally relevant CO 2 concentrations. It appears that the floating leaves possess both aquatic and terrestrial properties and thus have 'the best of both worlds' so that floating leaves are particularly adapted to situations where the plant is partially submerged and occasionally experiences complete submergence.
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Affiliation(s)
- Dennis Konnerup
- The Freshwater Biological Laboratory, Department of Biology, University of Copenhagen, Universitetsparken 4, 3rd floor, 2100 Copenhagen, Denmark
| | - Ole Pedersen
- The Freshwater Biological Laboratory, Department of Biology, University of Copenhagen, Universitetsparken 4, 3rd floor, 2100 Copenhagen, Denmark
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Shao H, Gontero B, Maberly SC, Jiang HS, Cao Y, Li W, Huang WM. Responses of Ottelia alismoides, an aquatic plant with three CCMs, to variable CO2 and light. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:3985-3995. [PMID: 28369629 PMCID: PMC5853927 DOI: 10.1093/jxb/erx064] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 02/03/2017] [Indexed: 05/29/2023]
Abstract
Ottelia alismoides is a constitutive C4 plant and bicarbonate user, and has facultative crassulacean acid metabolism (CAM) at low CO2. Acclimation to a factorial combination of light and CO2 showed that the ratio of phosphoenolpyruvate carboxylase (PEPC) to ribulose-bisphosphate carboxylase/oxygenase (Rubisco) (>5) is in the range of that of C4 plants. This and short-term response experiments showed that the activity of PEPC and pyruvate phosphate dikinase (PPDK) was high even at the end of the night, consistent with night-time acid accumulation and daytime carbon fixation. The diel acidity change was maximal at high light and low CO2 at 17-25 µequiv g-1 FW. Decarboxylation proceeded at ~2-3 µequiv g-1 FW h-1, starting at the beginning of the photoperiod, but did not occur at high CO2; the rate was greater at high, compared with low light. There was an inverse relationship between starch formation and acidity loss. Acidity changes account for up to 21% of starch production and stimulate early morning photosynthesis, but night-time accumulation of acid traps <6% of respiratory carbon release. Ottelia alismoides is the only known species to operate CAM and C4 in the same tissue, and one of only two known aquatic species to operate CAM and bicarbonate use.
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Affiliation(s)
- Hui Shao
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
| | - Brigitte Gontero
- Aix Marseille Univ CNRS, BIP UMR, IMM, FR, Chemin Joseph Aiguier, Marseille Cedex, France
| | - Stephen C Maberly
- Lake Ecosystems Group, Centre for Ecology & Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster, UK
| | - Hong Sheng Jiang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
- Aix Marseille Univ CNRS, BIP UMR, IMM, FR, Chemin Joseph Aiguier, Marseille Cedex, France
| | - Yu Cao
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
- Hubei Key Laboratory of Wetland Evolution & Ecological Restoration, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
| | - Wei Li
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
- Hubei Key Laboratory of Wetland Evolution & Ecological Restoration, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
| | - Wen Min Huang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
- Hubei Key Laboratory of Wetland Evolution & Ecological Restoration, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
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Borum J, Pedersen O, Kotula L, Fraser MW, Statton J, Colmer TD, Kendrick GA. Photosynthetic response to globally increasing CO2 of co-occurring temperate seagrass species. PLANT, CELL & ENVIRONMENT 2016; 39:1240-1250. [PMID: 26476101 DOI: 10.1111/pce.12658] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Revised: 09/14/2015] [Accepted: 10/05/2015] [Indexed: 06/05/2023]
Abstract
Photosynthesis of most seagrass species seems to be limited by present concentrations of dissolved inorganic carbon (DIC). Therefore, the ongoing increase in atmospheric CO2 could enhance seagrass photosynthesis and internal O2 supply, and potentially change species competition through differential responses to increasing CO2 availability among species. We used short-term photosynthetic responses of nine seagrass species from the south-west of Australia to test species-specific responses to enhanced CO2 and changes in HCO3 (-) . Net photosynthesis of all species except Zostera polychlamys were limited at pre-industrial compared to saturating CO2 levels at light saturation, suggesting that enhanced CO2 availability will enhance seagrass performance. Seven out of the nine species were efficient HCO3 (-) users through acidification of diffusive boundary layers, production of extracellular carbonic anhydrase, or uptake and internal conversion of HCO3 (-) . Species responded differently to near saturating CO2 implying that increasing atmospheric CO2 may change competition among seagrass species if co-occurring in mixed beds. Increasing CO2 availability also enhanced internal aeration in the one species assessed. We expect that future increases in atmospheric CO2 will have the strongest impact on seagrass recruits and sparsely vegetated beds, because densely vegetated seagrass beds are most often limited by light and not by inorganic carbon.
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Affiliation(s)
- Jens Borum
- Freshwater Biological Laboratory, Department of Biology, University of Copenhagen, Universitetsparken 4, 3rd floor, 2100, Copenhagen, Denmark
| | - Ole Pedersen
- Freshwater Biological Laboratory, Department of Biology, University of Copenhagen, Universitetsparken 4, 3rd floor, 2100, Copenhagen, Denmark
- Institute of Advanced Studies, The University of Western Australia, Crawley, 6009, WA, Australia
- School of Plant Biology, The University of Western Australia, Crawley, 6009, WA, Australia
| | - Lukasz Kotula
- School of Plant Biology, The University of Western Australia, Crawley, 6009, WA, Australia
| | - Matthew W Fraser
- School of Plant Biology, The University of Western Australia, Crawley, 6009, WA, Australia
- Oceans Institute, The University of Western Australia, Crawley, 6009, WA, Australia
| | - John Statton
- School of Plant Biology, The University of Western Australia, Crawley, 6009, WA, Australia
- Oceans Institute, The University of Western Australia, Crawley, 6009, WA, Australia
| | - Timothy D Colmer
- School of Plant Biology, The University of Western Australia, Crawley, 6009, WA, Australia
| | - Gary A Kendrick
- School of Plant Biology, The University of Western Australia, Crawley, 6009, WA, Australia
- Oceans Institute, The University of Western Australia, Crawley, 6009, WA, Australia
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Raven JA, Colmer TD. Life at the boundary: photosynthesis at the soil-fluid interface. A synthesis focusing on mosses. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:1613-23. [PMID: 26842980 DOI: 10.1093/jxb/erw012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Mosses are among the earliest branching embryophytes and probably originated not later than the early Ordovician when atmospheric CO2 was higher and O2 was lower than today. The C3 biochemistry and physiology of their photosynthesis suggests, by analogy with tracheophytes, that growth of extant bryophytes in high CO2 approximating Ordovician values would increase the growth rate. This occurs for many mosses, including Physcomitrella patens in suspension culture, although recently published transcriptomic data on this species at high CO2 and present-day CO2 show down-regulation of the transcription of several genes related to photosynthesis. It would be useful if transcriptomic (and proteomic) data comparing growth conditions are linked to measurements of growth and physiology on the same, or parallel, cultures. Mosses (like later-originating embryophytes) have been subject to changes in bulk atmospheric CO2 and O2 throughout their existence, with evidence, albeit limited, for positive selection of moss Rubisco. Extant mosses are subject to a large range of CO2 and O2 concentrations in their immediate environments, especially aquatic mosses, and mosses are particularly influenced by CO2 generated by, and O2 consumed by, soil chemoorganotrophy from organic C produced by tracheophytes (if present) and bryophytes.
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Affiliation(s)
- John A Raven
- Permanent address: Division of Plant Sciences, University of Dundee at the James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK School of Plant Biology, The University of Western Australia, M084, 35 Stirling Highway, Crawley, WA 6009, Australia
| | - Timothy D Colmer
- School of Plant Biology, The University of Western Australia, M084, 35 Stirling Highway, Crawley, WA 6009, Australia
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Comparing photosynthetic characteristics of Isoetes sinensis Palmer under submerged and terrestrial conditions. Sci Rep 2015; 5:17783. [PMID: 26634994 PMCID: PMC4669503 DOI: 10.1038/srep17783] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 11/04/2015] [Indexed: 01/29/2023] Open
Abstract
Crassulacean acid metabolism (CAM) is widespread in terrestrial and aquatic species, plastic in response to environmental changes. Isoetes L. is one of the earliest basal vascular plants and CAM is popular in this genus. Isoetes sinensis Palmer is an amphibious species, alternating frequently between terrestrial and aquatic environments. Given this, we investigated and compared photosynthetic characteristics over a diurnal cycle under submerged condition (SC) and terrestrial condition (TC). The results suggest that I. sinensis possesses a stronger CAM capacity under SC. Compared with under TC, titratable acidity levels and organic acid concentrations were more enriched under SC, whereas soluble sugar or starch and protein levels were lower under SC. Transcript analyses for nine photosynthetic genes revealed that CAM-associated genes possessed high transcripts under SC, but C3-related transcripts were highly expressed under TC. In addition, the enzyme activity measurements demonstrated that PEPC activity over a diurnal cycle was slightly higher under SC, whereas Rubisco activity during the daytime was greater under TC. This comprehensive study probably facilitates general understandings about the CAM photosynthetic characteristics of Isoetes in response to the environmental changes.
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Konnerup D, Moir-Barnetson L, Pedersen O, Veneklaas EJ, Colmer TD. Contrasting submergence tolerance in two species of stem-succulent halophytes is not determined by differences in stem internal oxygen dynamics. ANNALS OF BOTANY 2015; 115:409-18. [PMID: 25471094 PMCID: PMC4332606 DOI: 10.1093/aob/mcu216] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Revised: 05/27/2014] [Accepted: 09/03/2014] [Indexed: 05/29/2023]
Abstract
BACKGROUND AND AIMS Many stem-succulent halophytes experience regular or episodic flooding events, which may compromise gas exchange and reduce survival rates. This study assesses submergence tolerance, gas exchange and tissue oxygen (O2) status of two stem-succulent halophytes with different stem diameters and from different elevations of an inland marsh. METHODS Responses to complete submergence in terms of stem internal O2 dynamics, photosynthesis and respiration were studied for the two halophytic stem-succulents Tecticornia auriculata and T. medusa. Plants were submerged in a glasshouse experiment for 3, 6 and 12 d and O2 levels within stems were measured with microelectrodes. Photosynthesis by stems in air after de-submergence was also measured. KEY RESULTS Tecticornia medusa showed 100 % survival in all submergence durations whereas T. auriculata did not survive longer than 6 d of submergence. O2 profiles and time traces showed that when submerged in water at air-equilibrium, the thicker stems of T. medusa were severely hypoxic (close to anoxic) when in darkness, whereas the smaller diameter stems of T. auriculata were moderately hypoxic. During light periods, underwater photosynthesis increased the internal O2 concentrations in the succulent stems of both species. Stems of T. auriculata temporally retained a gas film when first submerged, whereas T. medusa did not. The lower O2 in T. medusa than in T. auriculata when submerged in darkness was largely attributed to a less permeable epidermis. The submergence sensitivity of T. auriculata was associated with swelling and rupturing of the succulent stem tissues, which did not occur in T. medusa. CONCLUSIONS The higher submergence tolerance of T. medusa was not associated with better internal aeration of stems. Rather, this species has poor internal aeration of the succulent stems due to its less permeable epidermis; the low epidermal permeability might be related to resistance to swelling of succulent stem tissues when submerged.
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Affiliation(s)
- Dennis Konnerup
- School of Plant Biology and Institute of Advances Studies, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia and Freshwater Biological Laboratory, Institute of Biology, University of Copenhagen, Universitetsparken 4, 2100 Copenhagen, Denmark
| | - Louis Moir-Barnetson
- School of Plant Biology and Institute of Advances Studies, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia and Freshwater Biological Laboratory, Institute of Biology, University of Copenhagen, Universitetsparken 4, 2100 Copenhagen, Denmark
| | - Ole Pedersen
- School of Plant Biology and Institute of Advances Studies, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia and Freshwater Biological Laboratory, Institute of Biology, University of Copenhagen, Universitetsparken 4, 2100 Copenhagen, Denmark School of Plant Biology and Institute of Advances Studies, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia and Freshwater Biological Laboratory, Institute of Biology, University of Copenhagen, Universitetsparken 4, 2100 Copenhagen, Denmark School of Plant Biology and Institute of Advances Studies, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia and Freshwater Biological Laboratory, Institute of Biology, University of Copenhagen, Universitetsparken 4, 2100 Copenhagen, Denmark
| | - Erik J Veneklaas
- School of Plant Biology and Institute of Advances Studies, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia and Freshwater Biological Laboratory, Institute of Biology, University of Copenhagen, Universitetsparken 4, 2100 Copenhagen, Denmark
| | - Timothy D Colmer
- School of Plant Biology and Institute of Advances Studies, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia and Freshwater Biological Laboratory, Institute of Biology, University of Copenhagen, Universitetsparken 4, 2100 Copenhagen, Denmark
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Teakle NL, Colmer TD, Pedersen O. Leaf gas films delay salt entry and enhance underwater photosynthesis and internal aeration of Melilotus siculus submerged in saline water. PLANT, CELL & ENVIRONMENT 2014; 37:2339-2349. [PMID: 24393094 DOI: 10.1111/pce.12269] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 12/28/2013] [Accepted: 12/30/2013] [Indexed: 06/03/2023]
Abstract
A combination of flooding and salinity is detrimental to most plants. We studied tolerance of complete submergence in saline water for Melilotus siculus, an annual legume with superhydrophobic leaf surfaces that retain gas films when under water. M. siculus survived complete submergence of 1 week at low salinity (up to 50 mol m(-3) NaCl), but did not recover following de-submergence from 100 mol m(-3) NaCl. The leaf gas films protected against direct salt ingress into the leaves when submerged in saline water, enabling underwater photosynthesis even after 3 d of complete submergence. By contrast, leaves with the gas films experimentally removed suffered from substantial Na(+) and Cl(-) intrusion and lost the capacity for underwater photosynthesis. Similarly, plants in saline water and without gas films lost more K(+) than those with intact gas films. This study has demonstrated that leaf gas films reduce Na(+) and Cl(-) ingress into leaves when submerged by saline water - the thin gas layer physically separates the floodwater from the leaf surface. This feature aids survival of plants exposed to short-term saline submergence, as well as the previously recognized beneficial effects of gas exchange under water.
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Affiliation(s)
- Natasha Lea Teakle
- School of Plant Biology (M084), UWA Institute of Agriculture, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia; Centre for Ecohydrology, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia; Graduate Research School, Edith Cowan University, 270 Joondalup Drive, Joondalup, Western Australia, 6027, Australia
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Herzog M, Pedersen O. Partial versus complete submergence: snorkelling aids root aeration in Rumex palustris but not in R. acetosa. PLANT, CELL & ENVIRONMENT 2014; 37:2381-2390. [PMID: 24450988 DOI: 10.1111/pce.12284] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 01/15/2014] [Accepted: 01/16/2014] [Indexed: 06/03/2023]
Abstract
The root and shoot tissues of flood-tolerant wetland plants are highly porous to enable internal gas phase diffusion of O2 during waterlogging or submergence. In the case of only partial submergence (snorkelling), the atmosphere can act as source of O2 . The aim of this study was to assess the effect of waterlogging, partial submergence and complete submergence in the dark as well as in light on O2 partial pressure (pO2 ) in roots of Rumex palustris (flood tolerant) and R. acetosa (flood intolerant). We used O2 microelectrodes to measure pO2 of adventitious roots during manipulations of the water level around the shoot. Root pO2 in both species declined significantly upon submergence but remained oxic also when shoots were completely submerged in the dark (0.8 and 4.6 kPa in R. acetosa and R. palustris, respectively). The snorkelling effect was substantial in R. palustris only. Submergence in light had less impact on root pO2 and the effect of snorkelling was also minor. Hence, the benefits of light (underwater photosynthesis) and air contact (snorkelling) upon growth and survival in submerged wetland plants can now be linked to enhanced internal aeration.
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Affiliation(s)
- Max Herzog
- The Freshwater Biological Laboratory, Department of Biology, University of Copenhagen, Universitetsparken 4, 3rd Floor, Copenhagen, 2100, Denmark
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Colmer TD, Armstrong W, Greenway H, Ismail AM, Kirk GJD, Atwell BJ. Physiological Mechanisms of Flooding Tolerance in Rice: Transient Complete Submergence and Prolonged Standing Water. PROGRESS IN BOTANY 2014. [DOI: 10.1007/978-3-642-38797-5_9] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Cowling SA. Did early land plants use carbon-concentrating mechanisms? TRENDS IN PLANT SCIENCE 2013; 18:120-124. [PMID: 23102567 DOI: 10.1016/j.tplants.2012.09.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 09/05/2012] [Accepted: 09/26/2012] [Indexed: 06/01/2023]
Abstract
Carbon-concentrating mechanisms (CCMs) in plants involve actively increasing CO2 concentrations near ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO). The assumption has been that terrestrial plants did not evolve CCMs for well over 300 million years, yet most marine plants probably evolved CCMs at the time when oxygenic photosynthesis first occurred in the Paleozoic. One primary reason for this assumption is that analysis of genetic mutations for phosphoenolpyruvate carboxylase (PEPc; an enzyme required for C4 and CAM photosynthesis) indicate a molecular age of no more than 65 Ma. Could the evolutionary response of both RuBisCO and PEPc to varying concentrations of atmospheric CO2 and O2 over geological time have obscured the real time when land plants first used PEPc during photosynthesis?
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Affiliation(s)
- Sharon A Cowling
- Department of Earth Sciences, University of Toronto, 22 Russell Street, Toronto, Ontario, M5S 3B1, Canada.
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Colmer TD, Winkel A, Pedersen O. A perspective on underwater photosynthesis in submerged terrestrial wetland plants. AOB PLANTS 2011; 2011:plr030. [PMID: 22476500 PMCID: PMC3249690 DOI: 10.1093/aobpla/plr030] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Accepted: 11/23/2011] [Indexed: 05/03/2023]
Abstract
BACKGROUND AND AIMS Wetland plants inhabit flood-prone areas and therefore can experience episodes of complete submergence. Submergence impedes exchange of O(2) and CO(2) between leaves and the environment, and light availability is also reduced. The present review examines limitations to underwater net photosynthesis (P(N)) by terrestrial (i.e. usually emergent) wetland plants, as compared with submerged aquatic plants, with focus on leaf traits for enhanced CO(2) acquisition. SCOPE Floodwaters are variable in dissolved O(2), CO(2), light and temperature, and these parameters influence underwater P(N) and the growth and survival of submerged plants. Aquatic species possess morphological and anatomical leaf traits that reduce diffusion limitations to CO(2) uptake and thus aid P(N) under water. Many aquatic plants also have carbon-concentrating mechanisms to increase CO(2) at Rubisco. Terrestrial wetland plants generally lack the numerous beneficial leaf traits possessed by aquatic plants, so submergence markedly reduces P(N). Some terrestrial species, however, produce new leaves with a thinner cuticle and higher specific leaf area, whereas others have leaves with hydrophobic surfaces so that gas films are retained when submerged; both improve CO(2) entry. CONCLUSIONS Submergence inhibits P(N) by terrestrial wetland plants, but less so in species that produce new leaves under water or in those with leaf gas films. Leaves with a thinner cuticle, or those with gas films, have improved gas diffusion with floodwaters, so that underwater P(N) is enhanced. Underwater P(N) provides sugars and O(2) to submerged plants. Floodwaters often contain dissolved CO(2) above levels in equilibrium with air, enabling at least some P(N) by terrestrial species when submerged, although rates remain well below those in air.
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Affiliation(s)
- Timothy D. Colmer
- School of Plant Biology, The University of Western Australia, Crawley 6009, WA, Australia
| | - Anders Winkel
- School of Plant Biology, The University of Western Australia, Crawley 6009, WA, Australia
- Freshwater Biological Laboratory, University of Copenhagen, Helsingørsgade 51, 3400 Hillerød, Denmark
| | - Ole Pedersen
- School of Plant Biology, The University of Western Australia, Crawley 6009, WA, Australia
- Freshwater Biological Laboratory, University of Copenhagen, Helsingørsgade 51, 3400 Hillerød, Denmark
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Pedersen O, Pulido C, Rich SM, Colmer TD. In situ O2 dynamics in submerged Isoetes australis: varied leaf gas permeability influences underwater photosynthesis and internal O2. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:4691-700. [PMID: 21841181 PMCID: PMC3170561 DOI: 10.1093/jxb/err193] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 05/17/2011] [Accepted: 05/18/2011] [Indexed: 05/19/2023]
Abstract
A unique type of vernal pool are those formed on granite outcrops, as the substrate prevents percolation so that water accumulates in depressions when precipitation exceeds evaporation. The O(2) dynamics of small, shallow vernal pools with dense populations of Isoetes australis were studied in situ, and the potential importance of the achlorophyllous leaf bases to underwater net photosynthesis (P(N)) and radial O(2) loss to sediments is highlighted. O(2) microelectrodes were used in situ to monitor pO(2) in leaves, shallow sediments, and water in four vernal pools. The role of the achlorophyllous leaf bases in gas exchange was evaluated in laboratory studies of underwater P(N), loss of tissue water, radial O(2) loss, and light microscopy. Tissue and sediment pO(2) showed large diurnal amplitudes and internal O(2) was more similar to sediment pO(2) than water pO(2). In early afternoon, sediment pO(2) was often higher than tissue pO(2) and although sediment O(2) declined substantially during the night, it did not become anoxic. The achlorophyllous leaf bases were 34% of the surface area of the shoots, and enhanced by 2.5-fold rates of underwater P(N) by the green portions, presumably by increasing the surface area for CO(2) entry. In addition, these leaf bases would contribute to loss of O(2) to the surrounding sediments. Numerous species of isoetids, seagrasses, and rosette-forming wetland plants have a large proportion of the leaf buried in sediments and this study indicates that the white achlorophyllous leaf bases may act as an important area of entry for CO(2), or exit for O(2), with the surrounding sediment.
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Affiliation(s)
- Ole Pedersen
- Freshwater Biological Laboratory, Department of Biology, University of Copenhagen, Helsingørsgade 51, DK-3400 Hillerød, Denmark.
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