Exogenous α-tocopherol has a beneficial effect on Glycine max (L.) plants irrigated with diluted sea water

Abstract

Summary -Tocopherol (TOC) is a vitamin and anti-oxidant compound which plays an important role in alleviating a number of abiotic stresses, including salinity. A pot experiment was conducted at the National Research Centre, Dokki, Giza, Egypt to study the responses of soybean plants (Glycine max L. ‘Giza 111’) to three foliar spray applications of 100 mg l-1 TOC while grown under irrigation with sea water mixed with fresh water (SW-FW) to obtain electrical conductivities of 0.23, 3.13, or 6.25 dS m-1. The net assimilation rate (NAR) of photosynthate, relative growth rate (RGR), chlorophyll a/b ratio, and concentrations of free proline, total free amino acids, total soluble sugars, nitrogen (N), and sodium ions (Na+) increased progressively with increasing salinity. In contrast, relative water contents, and leaf concentrations of photosynthetic pigments, phosphorus (P), and potassium ions (K+), and K+:Na+ ratios, declined gradually with increasing salinity. Three foliar spray applications of 100 mg l-1 TOC increased the NAR, the RGR, and N concentrations, and showed variable but positive changes in all other parameters measured under irrigation with SW-FW at different levels of salinity. Based on the above results, we recommend the use of 100 mg l-1 TOC as a commercial formulation to enhance the growth and productivity of soybean plants when grown under irrigation with moderately saline water (EC < 6.25 dS m-1).