Beneficial Effect of Melatonin on Growth and Chlorophyll Content in Wheat (Triticum aestivum L.) Grown Under Salt Stress Conditions

Melatonin (Mel) is an essential molecule that regulates plant growth and development and alleviates the damaging effects of various environmental stressors, including salinity. Nevertheless, the mechanism of melatonin in mediating salt stress response of wheat seedlings still needs to be explored. Therefore, the present study aimed to investigate melatonin's performance on some morpho-physiological attributes in wheat grown under salinity stress. In half-strength Hoagland solution (HS), two wheat cultivars, i.e Khaista-17 and Shahkar-13 were exposed to sodium chloride (NaCl) at 200 mM, no salt stress (control), Melatonin (200 mu M) and Melatonin (200 mu M) + NaCl (200 mM) for 15 days. Treatments were arranged in a 3-factorial completely randomized design (CRD) with three replicates for each treatment. After every 3-day treatment, data were recorded on plant height, total fresh weight, shoot weight, root weight, and chlorophyll content. Results revealed that exogenous supplementation with melatonin under salinity stress significantly improved both wheat cultivars' growth and physiological attributes (i.e. chlorophyll contents). Compared to salinity alone, the combined application of melatonin and sodium chloride increased total fresh weight by 17 and 23%, respectively, for both Shahkar-13 and Khaista-17 cultivars. Furthermore, melatonin (without NaCl) had the highest chlorophyll index (44), and the chlorophyll contents were enhanced to 25 and 37% by 200 mu M melatonin combined with NaCl in both wheat cultivars, respectively. As a result, it could be concluded that the exogenous application of melatonin at 200 mu M had a pronounced effect on the performance of wheat plants grown under salinity conditions through alleviating the adverse effects of salinity stress.