Green-synthesized Fe₂O₃ and Ca(OH)₂ nanoparticles, Alongside Rosemary extract, Enhance growth, Antioxidant defense, and Secondary Metabolite Accumulation in Lupinus Termis (Forssk.)

Abstract

Lupinus termis (Forssk.) is a valuable leguminous plant, prized for its medicinal and nutritional properties. This study aimed to investigate the biochemical and physiological responses of lupine to elicitation using biosynthesized nanoparticles (NPs) and a plant-derived extract. Iron oxide (Fe₂O₃) and calcium hydroxide (Ca(OH)₂) NPs were synthesized via rosemary (Salvia rosmarinus Spenn.) leaf polyphenols. The efficacy of green synthesized NPs was compared to rosemary extract as separate elicitor treatments in a greenhouse experiment to increase plant growth and metabolism. Both the NPs and rosemary extract significantly enhanced growth, biomass and photosynthetic attributes, whereas the NPs induced greater growth activity. All treatments reduced malondialdehyde levels while increasing hydrogen peroxide, ascorbic acid, total antioxidant activity, and the activities of polyphenol oxidase and peroxidase. Additionally, Ca(OH)₂ NPs increased the levels of key polyphenols constituents (ellagic acid, syringenic acid and kaempferol); whereas Fe₂O₃ NPs increased quercetin and myricetin accumulation. Rosemary treatment induced the highest levels of chlorogenic acid and naringin. Both NPs and rosemary extract increased key alkaloids (lupinine and angustifoline) to remarkable levels, which correlated with secondary metabolism and PAL activation. Furthermore, NPs boosted endogenous auxins (IAA) and gibberellins (GA) via modulating abscisic acid (ABA) and salicylic acid (SA) levels, thereby improving hormonal homeostasis and growth. Because of its bioactive phenolic derivatives, rosemary markedly increased SA levels while lowering GA and ABA, which strengthened plant defense. These findings demonstrate that green-synthesized Fe₂O₃ and Ca(OH)₂ NPs, as well as rosemary extract, improved L. termis growth, stress tolerance, and nutraceutical compounds.