Melatonin mediated high-temperature tolerance at seedling stage in green gram (Vigna radiata L.)

Global warming is predicted to have a generally negative effect on food grain production. The emergence of seedlings, blooming, pod-filling stages and yield of the mung bean are affected by high-temperature stress. Melatonin is a multifunctional signaling molecule with antioxidant properties that plays a vital role in plant stress defense mechanism. With this knowledge, the experiment was conducted to identify the optimum melatonin concentration to mitigate the adverse effects of high temperature in green gram var CO 8 with a completely randomized design (CRD). The treatments consisted of soaking seeds with different melatonin concentrations, viz., 20, 40, 60, 80 and 100 μM. Seeds were sown in a pertidish and allowed to germinate. After 5 days, the seedlings were exposed to two different high-temperature stress following the temperature induction response (TIR) protocol in the growth chamber viz., Ambient + 2°C (40°C) and Ambient + 4°C (42°C). After stress period, the seedlings were allowed to recover at room temperature for 2 days. At the end of the recovery period, observations on temperature tolerance-related traits viz., survival percentage, per cent reduction of shoot and root growth, cell viability, mortality per cent, malondialdehyde content, superoxide dismutase and catalase activity of green gram seedlings were assessed. Seeds pre-treated with melatonin of 100 and 80 µM exhibited higher survival percentage, shoot and root growth, cell viability and antioxidant enzyme activity (like superoxide dismutase and catalase) with reduced mortality per cent and malondialdehyde content under high-temperature stress at both 40°C and 42°C. The results revealed that seeds treated with different melatonin concentrations significantly improved green gram germination and seedling health.