Exogenous Growth Regulators and Water Stress Enhance Long-Term Storage Quality Characteristics of Onion

Exogenous growth regulators (GRs) play a crucial role in alleviating water stress and sustaining crop yields water-stressed areas. However, their effects on onions post-harvest quality, particularly post-monsoon onion—often preferred for long-term storage—were never studied. Therefore, this led us to investigate the interaction between GRs physiochemical functional quality attributes of during storage (9 months, at 25 ± 1 °C 65 5% RH). Onion was raised under four levels i.e., 1.00–0.85, 0.84–0.70, 0.69–0.40, 0.39–0.10 IW: CPE, designated as no, low, medium, severe stress, respectively, using line source sprinkler system (LSS). GR treatments include potassium nitrate (PN, 15 g L−1), sodium benzoate (SB, 100 mg thio-urea (TU, 450 ppm), gibberellic acid (GA, ppm). Results reveal that significant temporal changes dry matter, rehydration ratio, total soluble sugar (TSS), protein, phenolics content (TP) onion bulbs storage, indicate cumulative impact overall physicochemical status. Water increased biochemical attributes, especially pyruvic content, superoxide dismutase (SOD), peroxidase (POD) activity. Storage progressively decreased with increase period. Stressed onions, those produced condition, showed high weight losses, presenting poor keeping quality. application GRs, SB, TU, PN, reduced bulb losses together maintaining slightly better properties, thereby improving moderate level (0.69–0.40 IW:CPE). The exogenous is suggested key strategy ensuring its availability lean season.