Improving drought tolerance in rice seedlings through melatonin-induced alterations in root architecture, photosynthetic and antioxidant enzymes.

Drought stress impacts rice growth and development by altering the morphological, physiological and biochemical traits. The current study investigates the effect of melatonin (100 µM) mediated alteration on drought response in three varieties, viz., Pooja, Swarna and N22, in the seedling stage. The indicators of drought tolerance, such as leaf rolling score (LRS), leaf drying score (LDS), drought recovery score (DRS), root-shoot length, fresh and dry biomass, relative water content, photosynthesis-related parameter, osmolyte and antioxidant defence metabolites and enzymes, were studied. The results suggested that melatonin application reduced LRS, LDS and DRS and enhanced the drought recovery, with N22 having the highest tolerance. Melatonin also improved root and shoot growth, fresh and dry biomass, thereby ameliorating the detrimental effects of drought stress. Melatonin application also significantly improved root architecture, which ultimately leads to improvement of biomass accumulation in all three cultivars. Photosynthetic parameters, which include photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (Tr), and chlorophyll content, were suggested to decline under drought stress, but were significantly increased due to melatonin treatment, promoting photosynthetic efficiency. Further, drought stress increased proline and sugar content, which was reported to be modulated by the application of melatonin, thereby helping it for osmotic adjustment. The current study highlights melatonin's beneficial role, thereby providing drought tolerance by improving root morphology, photosynthesis and antioxidant machinery. These findings revealed that melatonin application could be an effective strategy for improving drought tolerance in rice. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-025-01663-6.