EFFECTS OF NaCl STRESS ON PROLINE METABOLISM, MALONDIALDEHYDE, GLYCINE BETAIN AND CHLOROPHYLL CONTENT IN SUNFLOWER PLANTS

The effects of NaCl changes in the free proline, pyrroline-5-carboxylate reductase (P-S-CR), proline oxidase (PO) and proline dehydrogenase (PDH) enzyme activities, glycine betaine and chlorophyll contents in salt tolerant and sensitive cultivars of sunflower. Significant proline accumulation was observed in both cultivars but it was more in salt tolerant sunflower plants under salt stress. PO, P-5-CR and PDH activities increased in tolerant cultivar and inhibited under salt stress in sensitive cultivar. The study indicated that while more glycine betaine, malondialdehyde accumulation was much less in tolerant cultivar. The levels of pigments, were similar amounts in both cultivars under salt stress. With these results, we can say that enhancing enzyme activities and proline levels during salt stress contributes significantly to the survival of plants. The salt tolerance of A-6535 is more pronounced in salt stress than in A-2517 when glycine betain (GB) is accumulated at high levels. In addition, the salt tolerance of A-6535 was shown in lower amounts of chlorophyll degredation. The physiological significance of these alterations can be assessed together with the functions of these enzymes in plant metabolism under salt stress.