Abstract:

【Objective】 The effects of water stress on photosynthesis and associated physiological characters of capsicum were studied, the aims were to reveal the relationship between photosynthetic traits and drought tolerance of two cultivars. 【Method】 The experiment was conducted under two water levels: no stress (75%-80% of field capacity) and stress (30%-40% of field capacity). The responses of plants growth, physiological changes, photosynthetic parameters, chlorophyll fluorescence, stomatal characters, ultrastructure of chloroplast were investigated. 【Result】 The results showed that, under the water stress condition, the growth of the plants was inhibited, the total plant dry weight declined significantly, and root/ shoot increased. Leaf water potential, leaf relative water content and leaf pigment decreased, the contents of malondialdehyde, the proline as well as the activities of superoxide dismutase and peroxidase increased. The Pn, Gs, Tr, Ci, ΦPSII, ETR and qP decreased, but the NPQ and WUE increased. The stomata became smaller and the density decreased, and most of them closed. The chloroplasts became round in shape, the lamellae arranged disorderly and the number of starch grain decreased or disappeared. 【Conclusion】 The decrease of net photosynthetic rate was considered as a result of stomatal restriction. The changes of photosynthetic parameters, chlorophyll fluorescence, stomata characters and the ultrastructure of chloroplast correlated significantly to drought resistance.

Key words: capsicum, water stress, photosynthesis, chlorophyll fluorescence, stomata, chloroplast