Abolition of photosystem I cyclic electron flow in Arabidopsis thaliana following thermal-stress

► Arabidopsis WT and its mutants, crr2-2 and pgr5, were subjected short-term exposure to heat stress in darkness. ► Our experimental results reveal for the first time that the impact of heat stress is significantly different in pgr5 mutant in comparison with crr2-2 mutant or WT plants. ► PSII centers of pgr5 mutants are shown less susceptible to high temperature stress if compared to crr2-2 mutant or WT plants as evidenced from the analyses of several Chl fluorescence parameters. ► Further, the redox kinetics of P700 obtained with far-red illumination in the mutants and WT Arabidopsis revealed a temperature dependent suppression of CEF by the thermal stress.