Polyphenolic and morphophysiological responses of different ajowan (Trachyspermum ammi L.) populations to Nano-silica and drought stress

This study investigated the effects of foliar application of Nano-silica (3 mM) on growth, yield, physiological traits, and phenolic accumulation in ajowan ( Trachyspermum ammi L.) under different irrigation regimes (50, 70, and 90% field capacity). Drought stress markedly reduced plant growth and productivity; however, Nano-silica application effectively alleviated these adverse effects. Across all irrigation treatments, Nano-silica significantly enhanced seed yield, harvest index, and key growth-related traits. Physiological assessments revealed that Nano-silica mitigated oxidative stress by decreasing hydrogen peroxide and malondialdehyde levels, while improving relative water content and chlorophyll content, thereby enhancing membrane stability and stress tolerance. HPLC analysis identified caffeic acid (15.08 ± 3.76 mg/100 g DW), rutin (13.26 ± 1.35 mg/100 g DW), and rosmarinic acid (12.63 ± 2.64 mg/100 g DW) as the predominant phenolic compounds. Moreover, Nano-silica promoted the accumulation of major phenolic metabolites, particularly under severe drought stress. Overall, foliar application of Nano-silica improved plant performance under water-deficit conditions by strengthening physiological resilience and stimulating phenolic biosynthesis. These findings highlight Nano-silica as a promising strategy to enhance drought tolerance, productivity, and medicinal quality of Trachyspermum ammi L. in water-limited environments.