Enhancing growth, flowering and bulb multiplication of Lilium by exogenous application of melatonin under acidic soils of Western Himalayas

Lilium holds a prominent position in the global floriculture industry due to its exceptional aesthetic appeal, wide range of colors, and versatility in both cut flower and potted plant markets. It is one of the most commercially valuable bulbous ornamentals, widely cultivated for its long vase life, elegant form, and fragrance. Melatonin is a multifunctional plant regulator that influences growth, development, and stress responses through complex and not yet fully elucidated signaling pathways. The Lilium plants were treated with different concentrations of melatonin, i.e.100 µM, 150 µM, 200 µM, 250 µM, 300 µM, and control, at 15 day intervals. A control was also maintained with water spray only. The effect of exogenous melatonin was significantly evident on plant height, total leaf area, leaf area index, and stem thickness. The maximum plant height (83.01 cm), total leaf area (961.46 cm²), leaf area index (2.40), stem thickness (8.50 mm), bud size (9.12 cm), flower size (14.72 cm), and vase life (13.50 days) were obtained with the 250 µM melatonin treatment. Total biomass (41.20%), above-ground biomass (58.93%), and below-ground biomass (29.60%) were also increased significantly in comparison to the control. The highest concentrations of chlorophyll a, chlorophyll b, and total chlorophyll in the leaves were observed with the 250 µM treatment, showing increases of 4.28%, 10.70% and 6.52%, respectively. Melatonin @ 250 µM significantly increased bulb weight (21.23%), bulb circumference (87.16%), number of bulblets (34.69%), and weight of bulblets (58.03%). A positive correlation was observed for vegetative, flowering, and bulbous traits. The results clearly indicate positive control of growth and development in Lilium crop by exogenous melatonin thus opening a new vista for improving the yield and quality of Lilium bulb at commercial scale.