Moringa (Moringa oleifera) green-synthesized copper oxide nanoparticles for the drought tolerance of tomato (Solanum lycopersicum)

The increasing impacts of climate change, global warming, and water scarcity are intensifying drought risk and compromising global food security. To mitigate these challenges, green-synthesized nanoparticles (NPs) derived from plant extracts have recently emerged as an innovative tool for enhancing crop resilience to abiotic stresses such as drought. Moringa enables eco-friendly nanoparticle production with diverse uses. Although Moringa enhances plant traits and its NPs have antimicrobial properties, limited research exists on their ability to improve plant tolerance to abiotic stress. Here, we investigated the potential of copper oxide (CuO) nanoparticles synthesized from Moringa plant extracts to alleviate drought stress in tomato plants (Solanum lycopersicum). The Moringa-based CuO NPs were characterized via UV‒Vis spectrophotometry, Zeta potential, FTIR, SEM, and TEM. Foliar applications of the NPs at various concentrations (3, 6, and 9 mg/L) were tested on tomato seedlings under normal and drought-induced conditions (10% PEG), alongside two controls: non-stressed control (water treatment) and drought stress control (PEG treatment). Physiological assessments showed that 6 mg/L Moringa-based CuO NPs were most effective under drought stress, significantly reducing leaf yellowing and increasing shoot length by 11%, root length by 21%, total dry biomass by 34% increase, and total chlorophyll content by 32% increase at (p < 0.05) compared to the drought stress control. Furthermore, at the molecular level, gene expression analysis revealed the upregulation of PAL, CHS, and HQT, which are genes critical to the stress response and secondary metabolism in tomato plants. Notably, the combination of CuO NPs with PEG amplified gene expression, indicating a synergistic effect on improving drought tolerance. These findings highlight the potential of the use of Moringa-synthesized CuO nanoparticles as a sustainable, eco-friendly strategy to mitigate drought stress in economic crops such as tomatoes. This new green approach offers a promising solution for bolstering food security in the face of climate change and water scarcity challenges.