Exogenous 24-Epibrassinolide (24-EBL) Enhances Morpho-physiological Traits in Wheat (Triticum aestivum L.) Genotypes under High Temperature Stress

Abstract

High temperature stress is one of the major constraints limiting wheat (Triticum aestivum L.) productivity worldwide. Brassinosteroids (BRs), a class of plant steroidal hormones, play a pivotal role in modulating plant growth and conferring tolerance to various abiotic stresses. The present study aimed to investigate the effects of foliar-applied 24-epibrassinolide (24-EBL) on morpho-physiological traits of heat-tolerant (HUW-510) and heat-susceptible (HUW-468) wheat genotypes grown under field conditions during the Rabi season of 2017–18. Treatments included three concentrations of 24-EBL (0.01, 0.02, and 0.03 mM) and a control, applied at pre-flowering (40 DAS) and post-flowering (65 DAS) stages. Morpho-physiological parameters were assessed at two critical growth stages, i.e., 65 and 85 days after sowing (DAS). Results revealed that 24-EBL significantly improved root length, shoot height, leaf number, leaf area, total dry weight, relative water content (RWC), and membrane stability index (MSI) compared to untreated control plants exposed to heat stress. Among the concentrations tested, 0.02 mM 24-EBL proved most effective in sustaining growth and physiological integrity. Furthermore, the tolerant genotype HUW-510 exhibited higher responsiveness than HUW-468 suggesting genotypic differences in BR-mediated thermotolerance. The findings highlight the potential application of 24-EBL as a sustainable approach for improving wheat resilience against high temperature stress.