| A study on the effects of heat stresses in sweet pepper was conducted in a growth chamber. The changes of some physiological and biochemical items in the leaves of cultivars of sweet pepper (heat-resistant Bei Jing Hai Hua 3 Hao, less heat-resistant Nan Jing 5-2 and heat-sensitive Bai Li 300) after heat stress was studied for the search of physiological foundation. The result showed:1. Under high temperature stress, seed vigor of sweet pepper was both decreased. However, the decreasing rate of heat-resistant cultivars were less than that of heat-sensitive ones. Thus, there is a possibility of using the changes in seed vigor as the indicators of assessing the heat resistance of various cultivars in sweet pepper.2. The water content was both decreased and transpiration was increased in sweet pepper. But the leaf cells in heat-resistant cultivars held more water content and bound water, with higher stomatal density, faster transpiration rate than in heat-sensitive ones. The changes of the physiological indexes in less heat-resistant sweet pepper were at intermediate levels as compared with those of the other two cultivars.3. Under high temperature stress, the growth was inhibited severely, root activity and Chlorophyll content were decreased, respiration of the leaf was enhanced, then decreased. The changes in heat-resistant were not obvious.4. The membrane damage extent, MDA content and the change of praline of the sweet pepper leaves under high temperature stress were suggested as the indicators of assessing the heat resistance of various cultivars in sweet pepper.5. After heat stress, the accumulation of O2-and H2O2 was increased, but the accumulation degree of heat-resistant was less than heat-sensitive ones; the activities of Catalase(CAT) increased obviously, Bei Jing Hai Hua 3 Hao was more than Nan Jing 5-2 and Bai Li 300; Superoxide dismutase(SOD) and Peroxidase(POD) was increased, then decreased, but the accumulation degree of heat-resistant was more than heat-sensitive ones; Reduced glutathione(GSH) increased and Ascorbic acid(ASA) content decreased in every one. The protection of enzyme and non- enzyme active oxygen scavenging system is more effective in the thermo-resistant cultivar than in others. |
