Photosynthetic response of two okra cultivars under salt stress and re-watering

Two cultivars of okra (Chinese green and Chinese red) were subjected to salt stress (0%, 6%, 12% and 18%) and equal proportions of NaCl and CaCl2 in Hoagland's nutrient solution and re-watering. Salt stress significantly reduced growth parameters and photosynthetic attributes of both cultivars. Treatment subjected to 18% salt stress caused 90% redundancy in growth parameters of both cultivars compared to control. Re-watering gave a positive response for plant growth of both cultivars in different levels. Chinese green showed better recovery at 6-0% re-watering level and Chinese red showed 12-6% and 6-0%, due to its salt tolerance nature. Considering re-watering water use efficiency and net photosynthetic rate the optimum values of salt tolerance for Chinese green and Chinese red were 8.3% and 12.02%, respectively. The best re-watering degree found as salt stress level ranged from 12.02% to 6% for Chinese red and 8.3% to 2.3% for Chinese green. This study provided a new method for the determination of irrigation time and quantification in crops.