Biochemical Changes of Coriander (Coriandrum sativum L.) Plants under Drought Stress and Foliar Application of Salicylic Acid and Silicon Nanoparticles

There is an increasing interest to use nanoparticles (NPs) and growth regulators in mitigating deleterious effects of the drought stress. The present work was conducted to investigate the effect of the salicylic acid (SA) and silicon (Si)-NPs on physiological and biochemical attributes of coriander (Coriandrum sativum L.) plants expose to drought stress. A split-plot experiment was carried out with irrigation regimes (irrigation after 60, 90, and 120 mm evaporation from Class A pan) as main plot and foliar application of SA and Si-NPs as the subplots during 2019 and 2020. The results showed drought stress reduced chlorophyll (Chl) content, but enhanced total soluble sugar (TSS), superoxide dismutase (SOD) and peroxidase (POX) activities of coriander leaves. Increases in Chl content, TSS, and activity of antioxidant enzymes were observed when plants sprayed with SA and Si-NPs. Moderate drought stress (90 mm evaporation from Class A pan) along with Si-NPs significantly increased total phenolic content (TPC) and total flavonoid content (TFC), essential oil (EO) content, and EO yield.  Foliar application of Si-NPs was more effective than SA to improve the antioxidant potential and EO yield of coriander plants when exposed to drought stress.