Effects of microplastics on growth and metabolism of rice (Oryza sativa L.)

Present work studied the impact of different doses of polystyrene (PS) and polyvinyl chloride (PVC) microplastics (MPs) on rice plants (Oryza sativa L.). Seven different treatments of PS and PVC MPs viz. D-0 (control), D-1-D-3 (0, 1.5, and 3.0 mg L-1 PS-MP) and D-4-D-6 (0, 1.5, and 3.0 mg L-1 PVC-MP) were given. In the experiment, sequential variations in growth, ionic homeostasis, and antioxidant metabolism in rice were monitored. Results show that compared to control, maximum repression in shoot and root and fresh and dry weight were recorded in D-6. We demonstrate that D-3 and D-6 reduced the photosynthetic rate up to 31.49 and 43.81% compared to D-0 while the transpiration rate was enhanced only under controlled conditions. Water use efficiency and internal CO2 concentration increased due to incremented doses of MPs. Decline in photosynthetic attributes directly corresponded with reduction in SPAD value (34.96%) at D-6. Besides, ionic homeostasis was perturbed and concentration of Ca, N, P, and K in root and shoot was imbalanced due to all levels of MPs and D-3 and D-6 were found most hazardous for these attributes. The resultant oxidative stress caused increment in MDA (49.26 and 138.44%) and H2O2, (66.72 and 125.18%) at D-3 and D-6, respectively. The maximum increase in SOD (109.08 and 146.08%), POD (232.59 and 289.23%), and CAT (182.65 and 242.89%) was estimated under D-3 and D-6, respectively as compared to control. Therefore, we concluded that PVC-MPs accumulation is potentially more devastating for rice growth and metabolism than PS-MPs. We recommend further research experimentats not only for translocation but also for tissue-specific retention of different sized MPs in crop plants to completely understand their influence on food safety.

Automated summary

This study investigated the effects of different doses of polystyrene (PS) and polyvinyl chloride (PVC) microplastics (MPs) on the growth, ionic homeostasis, and antioxidant metabolism of rice plants. Results showed that PVC-MPs accumulation had a more devastating impact on rice growth and metabolism compared to PS-MPs, with D-3 and D-6 being the most harmful treatments. Further research is recommended to fully understand the influence of different sized MPs on food safety.