Investigation of the effects of salt stress on oxidative stressparameters and antioxidant enzyme levels in pepper (Capsicum annuumL.) plant

Salinity is an important environmental stress that negatively affects plant growth and development. The aim of this study is to investigate the changes in oxidative stress parameters and antioxidant enzyme activities in pepper plants exposed to different levels of salt stress. Surface sterilized pepper seeds were germinated in peat-perlite mixture, and 10 days after germination, the seedlings were transferred to perlite-filled pots and watered with irrigation water containing different concentrations of NaCl (0, 50, 100, 150, 200 and 250 mM NaCl). At the end of the 8-week development period, the plants were harvested for analysis. Research findings showed that stem length, root length, upper part and root dry weight of plants decreased significantly due to increasing NaCl concentration. Additionally, increased salinity negatively affected the photosynthetic pigment content and maximum quantum yield (Fv/Fm) of pepper plants. Leaf relative water content decreased and proline accumulation increased. It has been observed that hydrogen peroxide (H2O2), malondialdehyde (MDA) and electrolyte leakage (ES) increase in plants under salt stress. When antioxidant enzyme activities were examined, it was determined that superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and peroxidase (POD) activities increased under salt stress,but tended to decrease above certain concentrations. The results reveal that salt stress negatively affects the physiological and biochemical parameters of pepper plants and that plants have developed various defense mechanisms to cope with this stress.