Effects of progesterone application on antioxidant enzyme activities and K+/Na+ ratio in bean seeds exposed to salt stress

This study aimed to investigate the influence of progesterone, a mammalian sex hormone, on germination of bean (Phaseolus vulgaris L.) seeds exposed to salt stress. The exogenous addition of 10(-6), 10(-8) and 10(-10) M progesterone to the stressing media in which bean seeds were germinated in combination with the salt (100 mM NaCl) stressor induced significant protective changes in the germination and early growth parameters. The mitigating effect of progesterone was evaluated by the measurement of radicle and plumule lengths, activities of antioxidant enzymes superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT). In addition, it is the first study that exhibited changes in K/Na ratio. The obtained results showed that progesterone application stimulated germination and growth of salt-stressed seeds. Similarly, it stimulated significantly SOD, POX and CAT activities compared to both control and salt control. Salt stress significantly increased the lipid peroxidation compared to the control seeds. However, parallel to the increase in antioxidant activity, lipid peroxidation was significantly reduced by progesterone application. The best stimulatory effects on investigated parameters were recorded at 10(-8) M progesterone-applied seeds. On the other hand, salt stress reduced remarkably K/Na ratio by 50% in radicle and by 80% in plumule. However, progesterone application significantly mitigated the reduction in K/Na ratio. These findings clearly demonstrate that progesterone has a positive role in moderate detrimental effects induced by salt.