Arsenic-triggered nano-hormonal responses modulate stomatal conductance, primary–secondary metabolites, and nutrient homeostasis in rice ( <i>Oryza sativa</i> L.)

A number of ecological stressors negatively impact on rice yield, drastically lowering crop productivity. Among these, arsenic stress is considered a major abiotic factor that affects number of processes in plants, ultimately leading to reduced productivity. Nano-hormonal interactions have garnered allure as a possible way to lessen arsenic toxicity in plants. In this work, the synergistic effects of zinc oxide nanoparticles (ZnO-NPs) and epibrassinolide (EBL) on rice (<i>Oryza sativa</i>) with arsenic stress were examined. A fully randomized block design (CRD) was used in a pot experiment. Exposure to arsenic (150<i>μ</i>m) impaired growth (length and biomass), photosynthetic performance, soluble sugars, starch, and sucrose (primary metabolites), phenolics and flavonoids (secondary metabolites), as well as key mineral nutrients. However, foliar application of ZnO-NPs (100 mg l^-1) and EBL (0.01<i>μ</i>m) alleviated arsenic-induced toxicity by promoting enzymes activity and promoting the involvement of secondary metabolites in defense. These improvements in the biochemical and physiological matrices of rice plants effectively mitigated growth losses under arsenic stress. Overall, this work concludes the interactions between ZnO-NPs and EBL in modulating development and growth in rice, thereby contributing to global food security.