Synergistic role of gamma-aminobutyric acid and melatonin in mitigating lead stress in rice

Lead (Pb) stress adversely affects plant growth, human health, and ecosystem sustainability. Gamma-aminobutyric acid (GABA) and melatonin (MT) emerged as key players to protect plants from abiotic stresses. However, effects of co-applying GABA and MT on glyoxalase system, osmolytes synthesis, secondry metabolites production, crop yield and soil properties not understood yet. The study was performed in a completely randomized design with three replications having. The stud involved following treatments; control, Pb stress (600 mg kg-1), Pb stress + GABA (1 mM), Pb stress + MT (100 µM), and Pb stress + GABA + MT. Rice variety (Zhongjiazao 17) grown under Pb stress faced a serious reduction in growth and yield due to excessive Pb accumulation and reduced chlorophyll and anthocyanin synthesis, antioxidant activities, and osmolytes and phenolic production. The foliar spray of GABA and MT boosted rice growth and productivity. This was strongly linked with reduced electrolyte leakage (EL), and malondialdehyde (MDA), and hydrogen peroxide (H2O2) and enhanced chlorophyll synthesis, antioxidants activity (70.66-129.97%), and osmolytes (proline, soluble proteins) synthesis, alongside a marked increase in phenolic (40.49%) and flavonoid (41.08%) compounds. Co-applying GABA and MT also decreased soil Pb availability and Pb accumulation in plant tissues, and increased nutrient uptake which favored better growth. These findings demonstrates that co-application of GABA and MT effectively mitigates Pb toxicity in rice by reducing Pb uptake, alleviating oxidative damages and regulating physiological and biochemical processes. Therefore, GABA and MT could be an eco-friendly strategies to remediate Pb polluted soils.