Multivariate Analysis of Maize Varieties: Roles of Ionomic Shifts, Antioxidant Defense, and Chloroplast Structural Integrity in Arsenic Stress Tolerance.

Arsenic stress poses a significant threat to maize (Zea mays L.) production by disrupting plant growth and physiological functions. This study employed multivariate analysis to identify arsenic-tolerant maize varieties, evaluating growth parameters such as shoot fresh weight, dry weight, plant height, chlorophyll content, and arsenic accumulation across 20 maize varieties exposed to 50 mg kg^-1. Significant variation in these indices enabled effective screening of arsenic tolerance. Cluster analysis based on D values classified GD562 and GD907 as highly tolerant, while GD911 and GD239 exhibited high sensitivity. GD562 exhibited enhanced tolerance by retaining calcium, zinc, iron, and sulphur in the roots, while redistributing nitrogen, phosphorus, potassium, and magnesium to the shoots, demonstrating superior nutrient management compared to the sensitive variety GD911. Additionally, GD562 showed elevated enzymatic antioxidant capacity (superoxide dismutase, peroxidase and glutathione reductase) at both the enzyme and gene expression levels, which alleviated oxidative damage by modulating reactive oxygen species. Additionally, enhanced soluble sugar accumulation contributed significantly to osmotic adjustment, thereby preserving cellular integrity under arsenic stress. Transmission electron microscopy analysis showed GD562 retained intact chloroplasts, thick cell walls, and stable vacuoles, highlighting its strong structural defense against arsenic toxicity, unlike the damaged cells of GD911. Collectively, these findings offer a holistic insight into the physiological, biochemical, ionomic and cellular mechanisms that underpin arsenic tolerance in maize, highlighting GD562's superior adaptive strategy under stress. This study emphasizes the importance of integrated analytical approaches for identifying arsenic resilient varieties, providing valuable insight for breeding programs and strategies to improving crop performance under heavy metal stress.