Regulation of Storage Reserve Mobilization and Energy Metabolism in Castor Seeds via ZnO ‐ NPs Priming Under Salt Stress

Salinity stress severely limits crop production, particularly in arid and semi-arid regions. This study explored the potential of zinc oxide nanoparticles (ZnO-NPs) as a priming agent to enhance castor (Ricinus communis) seedling growth under salt stress (100 mM NaCl), focusing on metabolic reprogramming and storage reserve mobilization. ZnO-NPs priming significantly improved seedling vigor by enhancing lipid mobilization, reducing triacylglycerol (TAG) accumulation, and promoting fatty acid breakdown, especially in the cotyledons. This was accompanied by upregulation of key enzymes in the glyoxylate and tricarboxylic acid (TCA) cycles, facilitating the conversion of stored lipids into soluble sugars for energy. Furthermore, priming restored ATP levels, particularly in the radicle, thereby improving energy metabolism. ZnO-NPs also mitigated oxidative stress, reducing lipid peroxidation and preserving membrane integrity. Transcriptomic analysis revealed upregulation of genes involved in lipid metabolism, stress responses, and energy conversion, supporting the biochemical changes observed. These findings highlight ZnO-NPs as a promising strategy to enhance seedling establishment and crop resilience under salt stress, contributing to sustainable agricultural practices and improved salt tolerance in oilseed crops.