SALT STRESS AFFECTS PHOTOSYNTHETIC EFFICIENCY AND CHLOROPLAST ULTRASTRUCTURE OF RICE LEAVES

Photosynthetic efficiency, structure and number of chloroplasts were investigated under salt stress in two rice cultivars (Pokkali, salt-tolerant, and Peta, salt-sensitive) .The results showed that with increasing external NaC1 concentration and prolonging treatment time, the number of chloroplasts of salt-sensitive cultivar Peta was evidently reduced, but the that of salt-tolerant cultivar Pokkali was not changed significantly. The aging of chloroplasts was accelerated and the lamellae of the grana and stroma were disintegrated gradually under salt stress. The size and number of osmiophilic granule were increased. The injure degree of chloroplasts of salt-tolerant cultivar Pokkali was lower than that of salt -sensitive cultivar Peta. The results indicated that the structure stability of chloroplast of pokkali was stronger than that of Peta under salt stress. The decrease of net photosynthetic rate and photochemical efficiency of PS Ⅱ (Fv/Fm) of salt-tolerant cultivars was less than that of salf-sensitive cultivars.