Abstract
Investigating the diurnal and seasonal variations of plant photosynthetic performance under future atmospheric CO2 conditions is essential for understanding plant adaptation to global change and for estimating parameters of ecophysiological models. In this study, diurnal changes of net photosynthetic rate (Anet), stomatal conductance (gs), and photochemical efficiency of PSII (Fv′/Fm′) were measured in two rice cultivars grown in the open-top-chambers at ambient (∼450 μmol mol–1) and elevated (∼650 μmol mol–1) CO2 concentration [(CO2)] throughout the growing season for 2 years. The results showed that elevated (CO2) greatly increased Anet, especially at jointing stage. This stimulation was acclimated with the advance of growing season and was not affected by either stomatal limitations or Rubisco activity. Model parameters in photosynthesis model (Vcmax, Jmax, and Rd) and two stomatal conductance models (m and g1) varied across growing stages and m and g1 also varied across (CO2) treatments and cultivars, which led to more accurate photosynthesis and stomatal conductance simulations when using these cultivar-, CO2-, and stage- specific parameters. The results in the study suggested that further research is still needed to investigate the dominant factors contributing to the acclimation of photosynthetic capacity under future elevated CO2 conditions. The study also highlighted the need of investigating the impact of other environmental, such as nitrogen and O3, and non-environmental factors, such as additional rice cultivars, on the variations of these parameters in photosynthesis and stomatal conductance models and their further impacts on simulations in large scale carbon and water cycles.
Highlights
Under the influence of human activities, atmospheric CO2 concentration [(CO2)] has been increasing to 415 μmol mol−1 in 2019 since the Industrial Revolution, before which the (CO2) was steadily maintained at about 280 μmol mol−1 (National Oceanic and Atmospheric Administration NOAA, 2019)
Rising (CO2) from 370 to 700 μmol mol−1 could offset the negative effect on photosynthesis due to 3.0–3.9◦C warming, but had larger negative effect on photosynthetic carboxylation capacity in warming condition compared with ambient air temperature (Lamba et al, 2018)
Diurnal changes of net photosynthetic rate (Anet), stomatal conductance, intercellular CO2 concentration (Ci) and chlorophyll a fluorescence characteristics were measured in two rice cultivars grown in the open-top-chambers at ambient (∼450 μmol mol−1) and elevated (∼650 μmol mol−1) CO2 concentrations throughout the growing season for 2 years
Summary
Under the influence of human activities, atmospheric CO2 concentration [(CO2)] has been increasing to 415 μmol mol−1 in 2019 since the Industrial Revolution, before which the (CO2) was steadily maintained at about 280 μmol mol−1 (National Oceanic and Atmospheric Administration NOAA, 2019). Soil-Plant-Atmosphere-Research (SPAR) showed that rising (CO2) from 350 to 700 μmol mol−1 increased rice growth, grain yield and canopy photosynthesis and increased the final aboveground biomass by 29% with sufficient irrigation (Baker and Allen, 2005). Rising (CO2) from 370 to 700 μmol mol−1 could offset the negative effect on photosynthesis due to 3.0–3.9◦C warming, but had larger negative effect on photosynthetic carboxylation capacity in warming condition compared with ambient air temperature (Lamba et al, 2018). The combination of rising (CO2) and temperature increased the photosynthesis but decreased yield for rice (Cai et al, 2016). The yield reduction under the combination of 200 μmol mol−1 above ambient (CO2) and 1◦C warming was reported in another research and the decrease of spikelet density might be the dominant factor (Wang W. et al, 2018)
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