Chemical role of α-tocopherol in salt stress mitigation by improvement in morpho-physiological attributes of sunflower (Helianthus annuus L.)

Elevated concentrations of salts in soil and water represent abiotic stresses. It considerably restricts plant productivity. However, the use of alpha-tocopherol (alpha-toc) as foliar can overcome this problem. It can improve crop productivity grown under salinity stress. Limited literature is documented regarding its optimum foliar application on sunflower. That's why the need for the time is to optimize alpha-toc foliar application rates for sunflower cultivated in salt-affected soil. A pot experiment was performed to select a better alpha-toc foliar application for mitigation of salt stress in different sunflower cultivars FH (572 and 621). There were 2 levels of salts, i.e., control (no salt stress) and sodium chloride (120 mM) and four alpha-toc foliar application (0, 100, 200, and 300 mg L-1). Results showed that foliar application of 100 mg/L- alpha-toc triggered the remarkable increase in fresh shoot weight, fresh root weight, shoot, and root lengths under salinity stress in FH-572 and FH-621 over 0 mg/L-alpha-toc. Foliar application of 200 mg/L-alpha-toc was most effective for improvement in chlorophyll a, chlorophyll b, total chlorophyll and carotenoids compared to 0 mg/L-alpha-toc. Furthermore, an increase in A was noted in FH-572 (17%) and FH-621 (22%) with alpha-toc (300 mg L-1) application under saline condition. In conclusion, the 100 and 200 mg/L-alpha-toc are the best application rates for the improvement in sunflower FH-572 and FH-621 growth, chlorophyll contents and gas exchange attributes. Further investigations are needed to select a better foliar application rate between 100 and 200 mg/L-alpha-toc at the field level under the different agro-climatic zone and soil types. (C) 2021 The Authors. Published by Elsevier B.V. on behalf of King Saud University.