Physiological and biochemical responses of okra (Abelmoschus esculentus) under salinity stress in Iran

Saline soil and water present significant agricultural challenges, particularly in arid and semi-arid regions like Iran. Around 15 % of Iran's land is categorized as saline. Salt stress disrupts various physiological processes in plants, leading to reduced crop yields. Considering the demand for food and the limitation of cultivated areas is rising, the cultivation of salt-resistant crops is gaining attention. This study was conducted to examine the morpho-physiological responses tolerance of a native cultivar of okra (Abelmoschus esculentus L. cv. White Ahvazi) under conditions of salinity stress. Understanding how this native cultivar responds to salinity stress is crucial for increasing its productivity. The okra seedlings were subjected to seven different levels of electrical conductivity (EC) (1.7 as control, 4.4, 6.2, 8.5, 10.6, 12.5, 14.4, and 15.8 mS/cm) after the appearance of their first true leaves by dissolving NaCl salt in Hoagland's nutrient solution. The results showed that morphological traits in the treated samples were not significantly different from the non-treated samples until EC reached a value of 10.6 mS/cm. The increases in EC from 1.7 to 10.6 mS/cm resulted in a significant rise in the antioxidant capacity and content of biochemical constituents. While salinity stress from EC 12.5 mS/cm onwards caused significant induction of hydrogen peroxide free radicals and peroxidation of membrane lipids. The yield was also significantly reduced at ECs of 12.5, 14.4, and 15.8 mS/cm, which were 31.1, 40.6, and 59.6 % less than control plants, respectively. Increasing salinity stress resulted in a remarkable reduction of photosynthetic pigments in plants as compared to the non-treated plants. Generally, it can be concluded that the White Ahvazi cultivar of okra commonly cultivated in Iran had a moderate tolerance to EC with a threshold of 10.6 mS/cm. Thus, this study can contribute towards enhancing food production in regions facing challenges related to salinity.