THE EFFECT OF GA3 APPLICATIONS AT DIFFERENT DOSES ON LIPIDPEROXIDATION, CHLOROPHYLL, AND ANTIOXIDANT ENZYME ACTIVITIES IN PEPPER PLANTS UNDER SALT STRESS

The developmental and metabolic effects of gibberellic acid application in plants under salt stress was investigated by examining leaf antioxidant enzyme activities, MDA levels, and chlorophyll content. Pepper seedlings (Capsicum annuum cv. Demre) grown in water culture under controlled conditions were subjected to salt stress (100 mM NaCl) and/or GA(3) treatment (0, 5, 7.5, and 10 ppm). The activities of antioxidant defense system enzymes (superoxide dismutase, catalase, and ascorbate peroxidase) and the chlorophyll and malondialdehyde (MDA) contents were determined in leaves harvested on the 20th day of the experiment. GA(3) was applied to plants by adding GA(3) to the Hoagland nutrient solution. Salt and different doses of GA(3) applications to the pepper plants showed that the GA(3) doses at 5 and 7.5 ppm applied with salt partially inhibited plant growth and development and thus, protected plants against the oxidative stress caused by salt. The leaf antioxidant enzyme activities, MDA accumulation and chlorophyll content of GA(3) and salt-applied plants were considerably low compared to the salt only application. In the GA(3)-only application, the results were similar to those obtained in the control group (no salt, no GA(3)), except for the chlorophyll content. In the salt-only application, plant root and leaf weight, plant length and internode lengths were lower than those of the control group (no salt, no GA(3)), while the antioxidant enzyme activities and MDA and chlorophyll contents were higher than those of the control group (no salt, no GA(3)). In summary, GA(3) application to pepper plants partially suppressed the adverse effects of salt stress on plant development and metabolic activities. Therefore, GA(3) may provide direct or indirect protection against stress.