Cadmium Stress Mitigation in Different Cultivars of Spinach (Spinacea oleracea) with Foliar Application of Ascorbic Acid

Cadmium, a highly detrimental heavy metal, poses a significant threat to plant growth, leading to a decline in biomass production and potential risks to human health through the food chain. This study explores the impact of vitamin C (ascorbic acid) on the physio-biochemical attributes and metal tolerance of spinach crops. A completely randomized experiment with 72 pots (comprising three ascorbic acid treatments, four cadmium stress levels, two cultivars, and three replicates) was conducted to investigate the influence of foliar application of ascorbic acid on spinach and its mitigating effect on cadmium stress. The application of ascorbic acid demonstrated substantial improvements under cadmium stress conditions. Plant height, fresh and dry biomass increased significantly with foliar application of ascorbic acid when compared with untreated plants. Significant enhancements were observed in chlorophyll, carotenoids, anthocyanins, total soluble sugars, proteins, and ascorbic acid contents in both treatments. Furthermore, there was a notable reduction was observed in total flavonoids, total phenolics, malondialdehyde and hydrogen peroxide. The activity of ascorbate peroxidase, catalase, and peroxidase exhibited a decrease under both ascorbic acid treatment when compared with the control plants. Ascorbic acid also played a role in regulating essential mineral balance, increasing potassium while decreasing sodium concentrations and cadmium accumulation in treated plants. Foliar application of ascorbic acid not only improved spinach physiology but also mimicked cellular oxidative stress and reduced cadmium absorption. Future research on ascorbic acid application in vegetative plants holds potential for understanding its molecular aspect of antioxidant capabilities and hormonal regulation in cadmium-contaminated soil.