SALT-INDUCED OXIDATIVE STRESS IN CHLOROPLASTS OF PEA-PLANTS

The possible involvement of activated oxygen species in the mechanism of damage by NaCl stress was studied in chloroplasts from leaves of two cultivars of pea (Pisum sativum L.) with differential sensitivity to NaCl, Intact organelles were purified by centrifugation in density-gradients of Percoll. In chloroplasts from tolerant plants, NaCl stress produced a significant increase of CuZn-SOD II and ascorbate peroxidase activities as well as in ascorbate content, while in those from sensitive plants NaCl produced increases in the H2O2 content and lipid peroxidation and no changes were observed in the enzymatic activities. Chlorophyll content significantly decreased in chloroplasts from sensitive plants and chloroplast integrity was lower in sensitive than in tolerant plants, Electron microscopy showed that the thylakoidal structure of chloroplast was notably disorganized in the NaCl-treated leaves, In purified chloroplasts, an increase in the number and size of plastoglobuli was produced by NaCl in chloroplasts from tolerant plants and to a lesser extent, in chloroplasts from sensitive plants, The relative starch content only decreased in chloroplasts from tolerant plants by NaCl-treatment, Results obtained suggest that in the cellular toxicity of NaCl in pea plants, superoxide- and H2O2-mediated oxidative damage in chloroplasts may play an important role.