Photosynthetic Characteristic, Active Oxygen And Matter Metabolic Changes In Sweet Pepper During Water Stress And Recovery

The responses of photosynthetic characteristics and reactive oxygen species metabolism, along with changes in carbohydrate and soluble protein was studied in capsicum annuum cv.zhongjiao-5 and sujiao-5 during water stress and recovery. The effects of water stress on yields and quality in capsicum annuum cv.zhongjiao-5 at different growth stages was also studied. This study was carried out to offer a theoritial demonstration of scientific manage irrigation during the capsicum annuum cultivation. The main results were as follows,1 .With the enhancement of stress intensity, the adscisic acid (AsA), carotenoid (Car) contents and catalase (CAT) activity continuously decreased, while malondialdehyde (MDA) content continuously increased in leaves of both of capsicum annuum cultivars . On the second day after water withholding, superoxide dismutase (SOD) activities decreased, while superoxide radical (O2-) generation rate increased at this time. After rewatering and a period of recovery, Car contents increased and gradually arrived at the control levels, but still significantly higher MDA contents and SOD activities were in stressed plants than in controls. On the first day after water stress relief, AsA contents and CAT activities in stressed plants increased to near control levels. Some differences in change ROS mechanism during water stress and recovery were observed between two cultivars. They were revealed that O2- generation rate more slowly decreased in zhongjiao-5 than in sujiao-5 from the forth day of water withholding to the first day of rewatering, and SOD activities rapidly increased in zhongjiao-5 than in sujiao-5 during the recovery period, along with AsA contents increased in sujiao-5 in constrast to no alteration in zhongjiao-5 on the second day of rewatering, and CAT activities increased in sujiao-5 in constrast to no alteration in zhongjiao-5 on two to three days after rewatering. These results suggested that the balance of the ROS metabolism was disturbed, and the degree of peroxidation of membrance-lipids was imposed under water stress, however, the activities of enzyme in antioxidative defense system increased with proper water stress, but different cultivars have obviously different response mechanism under water stress .2. With the enhancement of stress intensity, stomatal conductance (Gs), transipirationrate (Tr), leaf water content (LWC) and net photosynthetic rate (Pn) were all continuously decreased. During water stress period, intercellular CO2 concentration (Ci) initially remained and then increased, but gradually returned to the control levels after rewatering. During water stress period, carboxylation efficiency (CE) continuously decreased, apparent quantum yield of carbon assimilation (c) significantly decreased only on the sixth day after water suspension, total chlorophyll (Chli) contents decrease, chlorophyll a (Chla) contents in stressed plants were remarkably lower than controls, and chlorophyll b (Chlb) contents hardly altered. During rewatering period, CE in stressed plants were significantly lower than controls, and c in stressed plants rapidly return to the control levels, Chl contents were still lower in stressed plants than controls. Some differences in change photosynthetic mechanism during water stress and recovery were observed between two cultivars. they were revealed that water use efficiency (WUE) were higher in zhongjiao-5, and lower in sujiao-5 than in controls from the forth day of water suspense to the first day after rewatering, and Chla contents increased but still remarkably lower in zhongjiao-5 than in controls after rewatering, while Chla contents in sujiao-5 were recovery on the second day of rewatering, Chlb contents more slowly decreased in zhongjiao-5 than in sujiao-5. These results showed that photosynthetic pigment degradated, photosynthetic efficiency decreased under water-stress, and decreases of CE, resulting in restriction of the process of carbon assimilation and fixation, contributed to the major limiting factor in reducation of photosynthetic rate in the...