Detached leaves of tomato differ in their photosynthetic physiological response to moderate high and low temperature stress

The potential use of photosynthetic physiological traits in detached leaves as assistant predictors of cutting quality understress condition was assessed. In this study, the effects of moderate high and low temperature stress on gas exchange, chlorophyll fluorescence and antioxidative enzyme activity were studied in detached leaves of tomato (Lycopersicon esculentum Mill. cv. 9021) plants. Detached intermediate leaves were subjected to 15, 25,and 35 degrees C for 5 d. Leaves at 15 degrees C exhibited similar photosynthetic characteristics to that at 25 degrees C while leaves at 35 degrees C showed significantly reduced net CO2 assimilation rate. The maximal photochemical efficiency (Fv/Fm), the quantum yield of the photosystem II ((Phi(PSII)) reaction centers and the efficiency of excitation capture of open PSII center (Fv'/Fm') were also reduced associated with increased ratio of Phi(PSII)/Phi(CO2) (quantum efficiency Of CO2 fixation) at 35 degrees C. Furthermore, exposure to high temperature caused a significant increase in the activities of ascorbate peroxidase (APX), superoxide dismutase (SOD), guaiacol peroxidase (G-POD) and the content of H2O2 and malonyldialdehyde (MDA), whereas there was no significant increase in the activities of catalase (CAT). Our results suggest that detached leaves of tomato differ in their photosynthetic physiological response to moderate high and low temperature stress, and photosynthetic physiological traits could be used as potential assistant predictors of cutting quality after storage under stress conditions in detached tomato leaves. (C) 2009 Elsevier B.V. All rights reserved.