Effect of short-term daytime sub-high temperature on antioxidant enzymes of tomato leaves.

In order to investigate the reason that daytime sub-high temperature influences photosynthesis of tomato leaves. The tomatoes were treated with daytime sub -high temperature (35℃ ) for 9 days during the 1st inflorescence flowering, 25℃ as control. The effects of sub-high temperature on net photosynthetic rate, chlorophyll content and activities of antioxidant enzymes of tomato leaves were studied. The results showed that: short-term sub-high temperature (35℃) treatment significantly reduced the net photosynthetic rate and chlorophyll content, at the end of the treatment, the net photosynthetic rate and chlorophyll content were lower than control for 26.27% and 33.07% respectively. The effects of sub-high temperature (35℃) on the activities of antioxidant enzymes were not the same, the activity of CAT was lower than control throughout. The activities of SOD and POD were increased at first and then decreased, when treated for 3 days, the activities of SOD and POD were higher than control, when treated for more than 6 days, the activities of SOD and POD were reduced. At the end of the treatment, the activities of SOD, POD and CAT were lower than control for 18.28%, 22.28% and 15.12% respectively. Short-term sub-high temperature (35℃) increased content of MDA, the content of MDA was higher than control throughout. The results indicated that Short-term sub-high temperature(35℃)could reduce photosynthetic ability of tomato leaves, lead to degradation of photosynthetic pigment, this is due to the activities of antioxidant enzymes are decreased which lead to aggravation of membrance lipid peroxidation, accumulation of active oxygen lead to the damages of cell membrane system and photosynthetic mechanism.