Functional and Molecular Responses of Rice to Foliar Application of Moringa oleifera Lam. Extracts With Contrasting...

The use of Moringa oleifera Lam. extracts (ME) as natural biostimulants has been increasingly recognized as an effective strategy to stimulate plant growth and improve nutrient utilization. In this study, alcoholic (ME_EtOH), hydroalcoholic (ME_H2O/EtOH), and aqueous (ME_H2O) leaf extracts were compared in terms of their physicochemical and nutritional properties, as determined by elemental analysis and NMR spectroscopy. The foliar bioactivity of these extracts was also evaluated in rice (Oryza sativa L.). The alcoholic extract showed a higher proportion of non-polar compounds and the highest C/N ratio (42:1), whereas the aqueous and hydroalcoholic extracts were richer in polar metabolites and essential minerals. Foliar application revealed distinct physiological responses in rice. The hydroalcoholic extract exhibited the strongest effects, significantly enhancing photosynthetic performance (a 16.8% increase in the chlorophyll a fluorescence performance index), upregulating nitrogen-assimilation genes, and increasing root and shoot biomass (≈approximately 29% higher root fresh weight) and fine-root formation (+25%). The aqueous extract induced slower but sustained improvements, resulting in moderate gains in photosynthetic efficiency and biomass accumulation, while the alcoholic extract showed more limited effects. All extracts increased leaf N, P, and K contents, indicating that growth promotion was driven mainly by physiological stimulation rather than direct nutrient supply. Overall, the results demonstrate that the extraction solvent strongly influences extract composition and bioactivity, with the hydroalcoholic formulation showing the greatest potential to enhance growth, photosynthetic metabolism, and nutrient-use efficiency in rice under greenhouse conditions, warranting further field validation.