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 tw o cultivars of pea (Pisum sativum L.) with differential sensitivity to NaCl, Intact organelles were purified by centrifugation in density-gr adients of Percoll. In chloroplasts from tolerant plants, NaCl stress produced a significant increase of CuZn-SOD II and ascorbate peroxidas e activities as well as in ascorbate content, while in those from sens itive plants NaCl produced increases in the H2O2 content and lipid per oxidation and no changes were observed in the enzymatic activities. Ch lorophyll content significantly decreased in chloroplasts from sensiti ve plants and chloroplast integrity was lower in sensitive than in tol erant plants, Electron microscopy showed that the thylakoidal structur e of chloroplast was notably disorganized in the NaCl-treated leaves, In purified chloroplasts, an increase in the number and size of plasto globuli was produced by NaCl in chloroplasts from tolerant plants and to a lesser extent, in chloroplasts from sensitive plants, The relativ e starch content only decreased in chloroplasts from tolerant plants b y NaCl-treatment, Results obtained suggest that in the cellular toxici ty of NaCl in pea plants, superoxide- and H2O2-mediated oxidative dama ge in chloroplasts may play an important role.