Integration of electron flow partitioning improves estimation of photosynthetic rate under various environmental conditions based on chlorophyll fluorescence
2021
Kitao, Mitsutoshi | Yasuda, Yukio | Kodani, Eiji | Harayama, Hisanori | Awaya, Y. (Yoshio) | Komatsu, Masabumi | Yazaki, Kenichi | Tobita, Hiroyuki | Agathokleous, Evgenios
Electron transport rate (ETR), estimated from chlorophyll fluorescence, is a widely-used indicator of photosynthetic activity. However, net photosynthetic CO₂ assimilation rate (A) does not linearly correlate with ETR when the fraction of electron partitioning into photosynthesis and photorespiration changes under fluctuating environmental conditions (CO₂, light, temperature and soil moisture).Here, we propose a practical approach to estimate A based on ETR with integration of stomatal conductance (gₛ) and leaf temperature, taking intercellular CO₂ concentration (Cᵢ)- and temperature-dependent electron partitioning into account.A estimated with the present approach was in good agreement with A measured under i) various CO₂ concentrations and light intensities in seedlings of Japanese beech and Japanese white birch, and ii) under 400 and 800 μmol mol⁻¹ CO₂ and temperatures of 15–40 °C, and iii) in progress of drought stress after a water withholding in seedlings of Japanese white birch. Furthermore, canopy-level CO₂ uptake could be estimated based on the spectroscopic and flux observations over a Japanese beech stand, under a wide range of environmental conditions.The present approach is advantageous because it does not require biochemical information, such as the maximum rates of Rubisco carboxylation and electron transport, providing a more forward approach to estimate terrestrial carbon flux through remote sensing approaches.
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