Role of 24-Epibrassinolide in Alleviating Drought Stress Through Biochemical and Physio-Morphological Adjustments in Tuberose (Polianthes tuberosa L.)

This study investigated the impacts of 24-epibrassinolide (24-EBL) on physio-morphological traits, water relations, biochemical attributes, and antioxidant enzyme activity in two tubrose cultivars with differential responses to drought stress. The 24-EBL was applied at five distinct concentration levels (0, 2, 4, 6, and 8 μM) to two cultivars of tuberose, Mexican single and Pearl double, under two irrigation intervals: a two-day interval and a five-day interval. Application of 2 μM 24-EBL with a five-day irrigation interval was most effective in enhancing growth traits, including plant height, length and diameter of the flowering stem, its fresh and dry mass, leaf area, shoot biomass (fresh and dry). This treatment also improved water-related physiological traits [leaf water potential (Ψw), osmotic potential (Ψπ), water use efficiency (WUE), and turgor potential (Ψp)] in addition to other traits such as photosynthesis, transpiration, stomatal conductance (gs), and chlorophyll contents, compared to other treatments. The activity of antioxidant enzymes [superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)] and biochemical attributes (proline and glycine betaine (GB)) were also regulated by foliar application of 24-EBL. It was concluded that 2 μM 24-EBL is an effective concentration for enhancing drought tolerance in tuberose, providing a valuable strategy for improving crop resilience under water-deficit conditions.