Effects of high temperature on seed germination and seedling growth and antioxidant system of tomato

Five different-thermotolerance tomato varieties(2583,Shenfen 8,Puhong 909,Shenfen 998,and Fen 2)were used as experimental materials,and the effects of high temperature at 33℃(28℃as control)on their seed germination and early-stage seedling growth were studied by comparative analysis. The results showed that the seed germination rate,germination vigor,germination index and vitality index of the tested varieties were significantly reduced under high temperature condition,and the lower the variety's thermotolerance,the more obvious the inhibiting effect of high temperature. High temperature also had a significant inhibiting effect on the early-stage seedling roots but little effect on the shoot length.High temperature led the seedlings' superoxide anion producing rate and MDA content to significantly increase and made the SOD,POD and CAT activities rise,though the varieties with comparatively low thermotolerance were smaller in the increments of POD and CAT activities and had less capacity to eliminate active oxygen.This indicated that the plants under high temperature could scavenge the active oxygen via increasing the antioxidant enzyme activity,and thus decrease the damage by membrane lipid peroxidation and ease the inhibiting effect of high temperature on early-stage tomato seedling growth.