Alleviation of drought stress damages by melatonin and associated with adjusting photosynthetic efficiency, antioxidative system, and anatomical structure of (L.).

These experiments were performed to study the effect of exogenous treatment with melatonin at 100 μM and seed treatment with (10 CFU/cm) on growth, physio-biochemical characters, antioxidant enzymes, and anatomical features of soybean plants cv. Giza 111 under drought conditions. The findings showed that leaves number, nodules number, branches number, relative water content (RWC), chlorophyll content, and maximum quantum efficiency of PSII (Fv/Fm) were significantly reduced in soybean under drought stress. In addition, anatomical structure of stems and leaves were negatively affected in stressed plants. Moreover, proline, electrolyte leakage (EL%) lipid peroxidation (MDA), superoxide (O ), hydrogen peroxide (HO), and antioxidant enzymes, such as catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD), were significantly increased under drought stress. However, application of melatonin or caused an improvement in growth characters, such as branches number, and increased chlorophyll and content, RWC as well as Fv/Fm in drought stressed soybean plants. Furthermore, melatonin and treatments showed a significant decrease in EL%, MDA, O and HO, besides regulating the activity of antioxidant enzymes under drought stress. The stems and leaves anatomical structure, such as lamina thickness, lower and upper epidermis thickness, number of xylem vessels/bundle, stem diameter, xylem vessels diameter, and phloem thickness, were improved under drought conditions with melatonin and treatments. Therefore, the outcomes of this investigation recommended the use of melatonin as foliar spray and as seed treatment, which could regulate a number of stress-responsive mechanisms to protect the stressed soybean plants, improve their growth under drought stress.