Integrative Evaluation of Silicon Application Methods for Drought Tolerance in Wheat Using Morpho-Physiological and Biochemical Markers

The current investigation emphasized the impact of various silicon (Si) application methods, including seed priming, fertigation, and foliar application, on the morpho-physiological and biochemical responses of two wheat cultivars, Nishan (drought-tolerant) and Faisalabad-2008 (drought-sensitive), under water-deficient conditions. The plants were cultivated under normal (100% field capacity) and drought-stressed (50% field capacity) regimes. Si application methods and water deficit significantly influenced growth, physiological performance, and biochemical traits. Foliar Si application emerged as the most effective strategy, enhancing shoot and root length, biomass accumulation, tiller production, spike length, and grain yield. Physiological parameters such as photosynthetic rate, stomatal conductance, and relative water content also improved notably with extrinsic silicon application, particularly under drought conditions. Biochemically, foliar-applied Si increased total soluble proteins and improved nitrogen metabolism while reducing the accumulation of drought-induced stress markers, including proline, total free amino acids, and total soluble sugars. Additionally, the chlorophyll and carotenoid contents were better preserved, indicating sustained photosynthetic efficiency. Antioxidant enzyme activities (SOD, POD, CAT, APX) were elevated under drought stress, with Si application reducing oxidative damage, especially in the sensitive genotype. Multivariate analyses, including principal component analysis (PCA), Pearson’s correlation, heatmaps, and the MGIDI index, consistently ranked foliar silicon (Si) as the most beneficial treatment in enhancing drought resilience. These findings demonstrate that foliar silicon application significantly improves the morphological and physio-biochemical tolerance of wheat to water deficit, offering a practical and efficient strategy to enhance crop performance and stability in water-limited regions.