Effect of Salicylic Acid on Growth and Physiological Status of Salt Stressed Sour Orange Seedlings (Citrus aurantium L.)

Abstract

A Pot experiment was conducted to determine the effect of exogenous salicylic acid (SA) application on growth, chlorophyll content, catalase (CAT) activity, peroxidase (POX) activity, cell membrane ionic permeability (electrolyte leakage), leaf and root K+ /Na+ ratio of sour orange seedlings grown under salt stress and greenhouse conditions. Sour orange seedlings were treated with SA at two concentrations (0.15mM as a foliar spray and 0.25mM as a soil application). Two treatments in both seasons were pre-treated with 0.15mM or 0.25mM of SA for one month before application of salinity treatment (acclimation treatment). Salinity treatments were established by irrigating seedlings twice a week with saline solution contained 0, 75, and 100mM of NaCl. Salt stress negatively affected plant growth and chlorophyll content of sour orange seedlings. However, seedlings treated with SA often had greater plant length, leaf area and total dry weight as well as higher chlorophyll content under salt stress. Leaf peroxidase enzyme activity (POX) was reduced in response to salt stress while electrolyte leakage was raised. SA treatments induced increases in CAT and POX activity and decreases in electrolyte leakage compared to the control under salt stress. With respect to the nutrient content, SA treatment as a foliar spray (0.15mM) increased the leaf and root K+ /Na+ ratio as compared with control. The greatest values for most measurements were often obtained by the 0.15mM SA as a foliar spray. The treatment with SA one month before salt treatment (acclimation) did not exhibit a pronounced effect in comparison with SA without acclimation. These findings suggest that the SA treatments can ameliorate the negative effect of salinity on the growth of sour orange seedlings