Foliar‐applied Silicon and its Nanoparticles Stimulate Physio‐chemical Changes to Improve Growth, Yield and Active Constituents of Coriander (Coriandrum Sativum L.) Essential Oil Under Different Irrigation Regimes

Purpose Silicon (Si) plays beneficial role in alleviating biotic and abiotic stresses but comparative investigations with Si nanoparticles (Si-NPs) under water restriction on medicinal plants is not recognized. The aim of this study was to observe the Si and Si-NPs effects on growth, physio-chemical attributes, and essential oil (EO) profile in aerial parts of coriander ( coriandrum sativum L.) under water stress. Methods A split-plot experiment was conducted with irrigation regimes (irrigation after 60, 90, and 120 mm evaporation from Class A pan) in the main plots and foliar application of Si (in the form of Na 2 SiO 3 ) and Si-NPs in the subplots during 2019 and 2020. Results The results represented drought particularly severe stress decreased biological yield and relative water content (RWC) but increased total soluble sugar (TSS). Both Si and Si-NPs improved plant growth and yield through improved RWC, TSS, total phenolic content (TPC) and total flavonoid content (TFC). Moderate drought stress with Si-NPs was highly effective on TPC, TFC, EO percentage and yield. The main EO constitutes were n-Decanal (20.8–27.6 %), 2E-Dodecanal (13.3–16.7 %), 2E-Decanal (13.9–18.7 %), 2E-Tridecen-1-al (7.3–10.5 %), Dodecanal (7.2–10.6 %), and n-Nonane (4.3–8.7 %). Heat map analysis (HMA) showed foliar application of Si and Si-NPs were significantly distinguished from control treatment, which was mainly explained by EO yield and TFC. Conclusions Foliar-applied Si-NPs was the rapidly and highly effective practice to reach the optimum antioxidant capacity and EO yield of coriander plants when experience moderate drought stress.