Integration of physiological and molecular analyses reveals that a plant-based biostimulant delays drought-induced leaf senescence & improves maize yield

Drought-induced senescence is a major cause of maize yield loss. While biostimulant priming improves stress tolerance, its molecular basis is unclear. Here we demonstrate that priming maize with the plant-derived biostimulant AgriPrime Stimulus (APS) delays drought-induced leaf senescence at reproductive-stage, resulting in improved cob weight and yield. Integrated physiological, transcriptomic, metabolomic, and phytohormone analyses revealed that APS priming preserves source leaf functionality by maintaining key metabolic processes. APS-primed drought-stressed leaves showed enrichment of photosynthesis-related genes and elevated levels of tricarboxylic acid cycle intermediates, indicating maintained carbon metabolism. APS priming also strengthened cell wall through the induction of genes involved in cellulose, hemicellulose, pectin, cutin, and wax biosynthesis, with increased structural metabolites such as xylose, mannose, and galactonic acid. Delayed senescence was further supported by enhanced redox homeostasis, with upregulation of antioxidant-related genes including superoxide dismutase (SOD3), peroxidases (PRXs), glutathione S-transferases (GSTs), and ascorbate-associated genes (BX13), together with increased levels of protective metabolites such as proline, trehalose, and myo-inositol. In parallel, APS priming suppressed proteolysis and senescence-associated genes (NYC1, NYE1, SAG39, NAC042). Integration of phytohormone and transcriptomic data further revealed maintained growth-promoting hormones alongside reduced abscisic acid and ethylene biosynthesis. Consistent with this reduced catabolic state, APS-primed leaves accumulated amino acids linked to growth, while unprimed drought-stressed leaves accumulated amino acids related to protein degradation. Collectively, these findings show that APS priming preserves source-sink relationships during drought by maintaining leaf longevity, and strengthening sink support, which improves cob weight under water deficit.