Gas exchange acclimation to elevated CO2 in upper-sunlit and lower-shaded canopy leaves in relation to nitrogen acquisition and partitioning in wheat grown in field chambers |
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| Institution: | 1. Instituto de Recursos Naturales y Agrobiología de Salamanca, CSIC, Apartado 257, 37071 Salamanca, Spain;2. Facultad de Ciencias Agrarias, Universidad de Talca, Casilla 747, Talca, Chile;1. Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Soil Ecology, Modeling Soil-Plant-Atmosphere Systems, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany;2. Water & Earth System Science (WESS) Competence Cluster, c/o University of Tübingen, Hölderlinstr. 12, 72074 Tübingen, Germany;3. Leibnitz-Zentrum für Agrarlandschaftsforschung e. V., Institute for Landscape Biogeochemistry, Eberswalder Straße 84, 15374 Müncheberg, Germany;4. University of Hohenheim, Institute for Landscape and Plant Ecology, Plant Ecology and Ecotoxicology, August-v.-Hartmann-Straße 3, 70599 Stuttgart, Germany;1. Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems and Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China;2. University of Chinese Academy of Sciences, Beijing 100039, China;1. School of Environment, Beijing Normal University, Beijing, 100875, China;2. Qinghai Academy of Animal Husbandry and Veterinary Science, Qinghai University, Xining, 810003, China;3. Northwest Institute of Plateau Biology, Chinese Academy of Science, Key Laboratory of Restoration Ecology of Cold Are in Qinghai Province, Xining, 810008, China;4. Tompkins Cortland Community College (TC3), Ithaca, New York, USA;1. CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, Liaoning, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;1. Agricultural Botany Department, Faculty of Agriculture, Fayoum University, 63514 Fayoum, Egypt;2. King Khalid University, Faculty of Science, Biology Department, Saudi Arabia;3. Soil and Water Department, Faculty of Agriculture, Fayoum University, 63514 Fayoum, Egypt;4. Environmental Sustainable Development Department, Environmental Studies & Researches Institute (ESRI), University of Sadat City, Egypt;5. Assiut University, Faculty of Science, Botany and Microbiology Department, Assiut, Egypt |
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| Abstract: | Growth at elevated CO2 often decreases photosynthetic capacity (acclimation) and leaf N concentrations. Lower-shaded canopy leaves may undergo both CO2 and shade acclimation. The relationship of acclimatory responses of flag and lower-shaded canopy leaves of wheat (Triticum aestivum L.) to the N content, and possible factors affecting N gain and distribution within the plant were investigated in a wheat crop growing in field chambers set at ambient (360 μmol mol?1) and elevated (700 μmol mol?1) CO2, and with two amounts of N fertilizer (none and 70 kg ha?1 applied on 30 April). Photosynthesis, stomatal conductance and transpiration at a common measurement CO2, chlorophyll and Rubisco levels of upper-sunlit (flag) and lower-shaded canopy leaves were significantly lower in elevated relative to ambient CO2-grown plants. Both whole shoot N and leaf N per unit area decreased at elevated CO2, and leaf N declined with canopy position. Acclimatory responses to elevated CO2 were enhanced in N-deficient plants. With N supply, the acclimatory responses were less pronounced in lower canopy leaves relative to the flag leaf. Additional N did not increase the fraction of shoot N allocated to the flag and penultimate leaves. The decrease in photosynthetic capacity in both upper-sunlit and lower-shaded leaves in elevated CO2 was associated with a decrease in N contents in above-ground organs and with lower N partitioning to leaves. A single relationship of N per unit leaf area to the transpiration rate accounted for a significant fraction of the variation among sun-lit and shaded leaves, growth CO2 level and N supply. We conclude that reduced stomatal conductance and transpiration can decrease plant N, leading to acclimation to CO2 enrichment. |
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