Application of Melatonin on Water Stress in Bean Plants (Phaseolus vulgaris L.)

This study evaluated the effect of exogenous melatonin application on the physiological, morphological, nutritional, and productive responses of green bean plants (cv. Strike) grown under four irrigation regimes (100, 85, 70, and 60% of the crop’s water requirements). Plants were grown in greenhouse conditions using a completely randomized design with eight treatments derived from the combination of irrigation level and melatonin application (100 μM). Melatonin application significantly improved several agronomic traits. Under full irrigation, leaf dry biomass increased by 98.3%, and marketable pod production increased by 56% compared to untreated plants. Total yield increased by 34.7% under optimal irrigation, while plants subjected to severe water deficit maintained higher productivity than untreated controls. The application of melatonin also increased the chlorophyll index by 48.2% compared to the untreated control. These findings demonstrate that melatonin improves drought tolerance by maintaining yield, nutrient uptake, biomass accumulation, and water use efficiency, representing a promising and sustainable strategy for improving green bean productivity under limited water availability.