Temperature Acclimation of Photosystem II Efficiency across Plant Functional Types and Climate

Abstract. Modelling terrestrial gross primary productivity (GPP) is central to predicting the global carbon cycle. Much interest has been focused on the environmentally induced dynamics of photosystem energy partitioning and how improvements in the description of such dynamics assist the prediction of light reactions of photosynthesis and therefore GPP. The maximum quantum yield of photosystem II (Φ_PSIImax) is a key parameter of the light reactions that influence the electron transport rate needed for supporting the biochemical reactions of photosynthesis. Φ_PSIImax is generally treated as a constant in biochemical photosynthetic models even though a constant Φ_PSIImax is expected only for non-stressed plants. We synthesized reported Φ_PSIImax values from Pulse-amplitude modulated fluorometry measurements in response to variable temperatures across the globe. We found that Φ_PSIImax is strongly affected by prevailing temperature regimes with declined values in both hot and cold conditions. To understand the spatiotemporal variability of Φ_PSIImax, we analysed the dependence of the temperature acclimation of Φ_PSIImax on plant functional type (PFT) and habitat climatology. The analysis showed that temperature acclimation of Φ_PSIImax is shaped more by climate than by PFT for plants with broad latitudinal distributions or in regions with extreme temperature variability. There is a trade-off between the temperature range within which Φ_PSIImax remains maximal and the overall rate of decline of Φ_PSIImax outside the temperature range such that species cannot be simultaneously tolerant and resilient to extreme temperatures. Our study points to a quantitative approach for improving electron transport and photosynthetic productivity modelling under changing climates at regional and global scales.