Effects of foliar application of different ascorbic acid concentrations on the response of sorghum to salinity.

A pot experiment was conducted during spring and summer of 2017 at collage of agriculture of Isfahan University of Technology, Esfahan, Iran, in order to evaluate the effects of different concentrations of foliar ascorbic acid application on the response of sorghum (speedfeed cultivar) to salinity. Treatments included two salinity levels (0 and 100 mM NaCl) and five concentrations of ascorbic acid (0, 50, 100, 150 and 200 mg/l). Treatments were arranged as factorial based on a completely randomized design with four replications. Salinity decreased potassium concentration, potassium/ sodium ratio, chlorophyll and carotenoid contents and shoot and root dry weights, while salt enhanced the concentrations of sodium and proline and the activities of antioxidant enzymes catalase, superoxide dismutase and ascorbate peroxidase. The decreases due to salinity at 0, 50, 100, 150 and 200 mg/l concentrations of ascorbic acid were 30, 27, 24, 27 and 20 percent, respectively. Foliar application of ascorbic acid improved plant growth parameters, the concentrations of proline and the activities of antioxidant enzymes while decreased sodium concentrations in sorghum plants. The highest increase in plant dry matter due to the application of ascorbic acid in both non-saline (30%) and saline (41%) conditions were obtained at 100 mg/l ascorbic acid. The increases due to ascorbic acid application in the antioxidant enzyme activity were greater for superoxide dismutase and ascorbate peroxidase as compared to catalase. Based on the results of this experiment, ascorbic acid application not only improved the growth of sorghum plants, but also alleviated the negative effects of salinity in this plant.