Mitigating drought and heavy metal stress in maize using melatonin and sodium nitroprusside

Drought and heavy metals (HMs) stress significantly impact maize (Zea mays L.), which is crucial for global food security. The aim of this study was to evaluate the effectiveness of sodium nitroprusside (SNP) and melatonin (MT) in alleviating the detrimental effects of drought and HMs’ stress on the growth and development of maize.

Maize plants were exposed to lead (Pb) and cadmium (Cd) under well-watered (WW), mild water stress (MWS), moderate water stress (MoWS), and severe water stress (SWS) conditions. The impact of these treatments on plant biomass, photosynthetic efficiency, antioxidant defense mechanisms, and water usage efficiency (WUE) was assessed.

Drought stress dramatically reduced plant biomass; under SWS compared to WW, fresh and dry weight decreased by up to 24% and 28%, respectively. Under MWS, fresh biomass was improved by 15% in the MT group and 13% in the SNP group, respectively. Dry weight was promoted by 17% in MT and 15% in SNP respectively. Statistical analysis revealed significant differences in biomass and photosynthetic efficiency (p < 0.05). MT and SNP boosted photosynthetic efficiency, triggered antioxidant defense mechanisms, and increased WUE by 20% under MWS and 43% under SWS. Under extreme water stress, MT and SNP reduced nutrient absorption losses, especially for potassium.

The results suggest that MT and SNP increase biomass production, photosynthetic efficiency, antioxidant activity, and nutrient absorption in maize, thereby enhancing resilience to drought and HM stress.