Rubisco deactivation and chloroplast electron transport rates co-limit photosynthesis above optimal leaf temperature in terrestrial plants

Net photosynthetic CO2 assimilation rate (A(n)) decreases at leaf temperatures above a relatively mild optimum (T-opt) in most higher plants. This decline is often attributed to reduced CO2 conductance, increased CO2 loss from photorespiration and respiration, reduced chloroplast electron transport rate (J), or deactivation of Ribulose-1,5-bisphosphate Carboxylase Oxygenase (Rubisco). However, it is unclear which of these factors can best predict species independent declines in A(n) at high temperature. We show that independent of species, and on a global scale, the observed decline in A(n) with rising temperatures can be effectively accounted for by Rubisco deactivation and declines in J. Our finding that A(n) declines with Rubisco deactivation and J supports a coordinated down-regulation of Rubisco and chloroplast electron transport rates to heat stress. We provide a model that, in the absence of CO2 supply limitations, can predict the response of photosynthesis to short-term increases in leaf temperature. Photosynthesis declines at mild temperatures in terrestrial plants. Here, the authors use published data to show that decline in photosynthetic CO2 assimilation rate with rising temperatures can be accounted for by Rubisco deactivation and declines in chloroplast electron transport rate.

Automated summary

Photosynthesis in plants declines at high leaf temperatures, which can be attributed to reduced CO2 conductance, increased loss from photorespiration and respiration, decreased chloroplast electron transport rate (J), and deactivation of Rubisco. However, the factors that best predict this decline are still unclear. This study shows that regardless of species, the decline in photosynthesis can be effectively explained by Rubisco deactivation and declines in J. A model is provided to predict the response of photosynthesis to short-term increases in leaf temperature in the absence of CO2 supply limitations.