Microplastic Contaminated Root Zone Supplementation With Ascorbic Acid Enhance Photosynthesis, Antioxidant Defense, ROS Scavenging, and Secondary Metabolites in Rice

Microplastics (MPs) are universally acknowledged as emerging contaminants in diverse environmental contexts, posing significant threats to ecosystem inhabitants and ecological balances. This study investigates the impact of various MP types on rice plants, while underlining the protective role of Ascorbic acid (AsA). Hydroponic experiments assessed four MP types: polyvinyl chloride (PVC), polyethylene terephthalate (PET), Polypropylene (PPL), and polyamide (PAD) against a control group, revealing substantial variations in rice plant responses to MP exposure. PVC exhibited the most pronounced effects, reducing shoot fresh-weight by 28.5% compared to the control. AsA significantly mitigated MP-induced damage, enhancing root and shoot weights, photosynthesis, and chlorophyll content. AsA application ameliorated the adverse impacts of MPs and enhanced the photosynthetic rate upto 14.4%, 10%, and 9.5% in PVC, PPL, and PET treatments, respectively. AsA also boosted metabolites like free amino acids, soluble proteins, and sugars, while reducing lipid peroxidation and oxidative stress markers i.e., malondialdehyde (MDA) and hydrogen peroxide. The highest concentration of peroxidase was seen in PPL treatment where a 36.3% increase was recorded compared to the control. Correlations between MPs and oxidative stress markers underscored MPs' deleterious impact. PPL, PET, and PAD also raised AsA up to 29.9%, 28.3%, 18.02% compared to the control, respectively. Overall, AsA effectively countered MPs' adverse effects, promoting rice growth, photosynthesis, and antioxidant defenses. Fragment-shaped MPs were particularly harmful. This study provides insights into the rice-MPs interface, vital for food safety and environmental conservation.