Role of Osmolyte Application in Regulating Physiological and Biochemical Traits for Osmotic Adjustment in Wheat Under Drought Stress

Osmolyte Application for Drought Stress Tolerance in Wheat

Abstract

Wheat (Triticum aestivum L.) yield is severely limited by drought, which disrupts water status, photosynthesis, osmotic balance and antioxidant defenses. This study evaluated the efficacy of foliar applied glycine betaine (GB; 50 and 100 mM) and putrescine (Put; 0.1 and 1 mM) at anthesis and post-anthesis in modulating physiological and biochemical traits across four wheat genotypes (MP 3288, GW 11, GW 451, GJW 463) under field-imposed drought. A split-plot design with three replicates was used, comparing well-watered control, drought stress, and drought plus osmolyte treatments. Key parameters relative water content (RWC), chlorophyll retention, free amino acids (FAA), total soluble sugars (TSS), proline, malondialdehyde (MDA), chlorophyll stability index (CSI), and yield components, were measured at anthesis and grain filling. Drought reduced RWC, chlorophyll content, and yield, while increasing FAA, TSS, proline and MDA. Foliar GB (100 mM) and Put (1 mM) effectively restored RWC toward control levels, preserved chlorophyll, enhanced osmolyte accumulation, limited lipid peroxidation and maintained chlorophyll stability. These treatments also recovered seed yield close to well-watered control. GW 11 exhibited the highest intrinsic drought tolerance, whereas GJW 463 showed the greatest relative gain from osmolyte sprays. The results demonstrate that timely foliar application of GB and Put at critical reproductive stages confers osmotic adjustment, membrane protection, and antioxidative reinforcement, thereby mitigating drought-induced yield losses in wheat.