Salinity-induced changes in key anti-oxidant enzyme activities and in the levels of some anti-oxidants, osmo-protectants, inorganic ions, and chlorophyll pigments in okra fruit (Abelmoschus esculentus L.)

To study the influence of NaCl stress on various biochemical components in okra (Abelmoschus esculentus L.) fruit, two differential cultivars, 'Nirali' and Posa Sawni', were grown under non-saline and saline conditions until fruit development. Salt treatment (50 mM or 100 mM NaCl) significantly decreased fresh fruit yields (by 47.5 - 67.7%), soluble protein contents (by 62.3 - 138.4%), K+ ion levels (by 17.7 - 29.0%), and peroxidase (POD) activity (by 17.7 - 44.6%) compared to fruit from non-saline treated okra plants. NaCl increased Na+ ion levels (by 47.9 - 118.8%), glycine betaine contents (GB; by 34.3 - 115.2%), H2O2 contents (by 4.14 - 64.4%), and ascorbic acid levels (by 73.0 - 109.0%) and superoxide dismutase (SOD) activity in the fruit of both okra cultivars. 'Nirali' had higher fresh fruit yields, K+ ion, GB, H2O2, and soluble protein contents, and higher SOD and POD activities, while 'Posa Sawni' fruit had higher ascorbic acid and total phenolic compounds contents and catalase (CAT) activity. Overall, the higher fresh yield of 'Nirali' could be attributed to enhanced levels of K+ ions, GB, soluble proteins, and SOD and POD activities. Fruit collected from all salt-stressed okra plants ('Nirali' and Posa Sawni') contained higher amounts of some key anti-oxidants and osmo-protectants which are considered beneficial for human health.