Differential Responses of Spinach Cultivars to Micro-Nanoplastic Stress Under Hydroponic and Soil Cultivation Conditions

To investigate the effects of micro-nanoplastics (MNPs) on spinach seed germination and sprout growth, this study employed polyvinyl chloride micro-nanoplastics (PVC-MNPs) as the treatment factor. Six concentration gradients were established under two cultivation conditions—hydroponic and soil. Two spinach cultivars grown in different seasons—the winter cultivar cv. xinbofeit and the autumn cultivar cv. connaught—were evaluated for germination characteristics, sprout morphology, and antioxidant capacity. Results indicated that low to moderate PVC-MNP concentration (1–100 mg/L in hydroponics or 0.1–1.0% in soil) moderately promoted seed germination and seedling growth, with cv. Xinbofeit exhibiting stronger stress tolerance. Conversely, high concentrations (200 mg/L in hydroponic or 2.0% in soil) inhibited germination and root development in both cultivars and induced oxidative stress responses. Principal component analysis identified germination rate, superoxide dismutase (SOD), and peroxidase (POD) activities as key response indicators. Significant inter-cultivar differences and cultivation method dependencies were observed: cv. xinbofeit showed higher sensitivity to elevated PVC-MNPs level, whereas cv. connaught demonstrated greater overall stress resistance. This study demonstrates that micro-nanoplastics exert a dual effect on spinach seed germination and sprout growth, with low to moderate concentrations promoting growth, while high concentrations inhibit development and induce oxidative stress. Moreover, significant differences in response were observed among different cultivars, highlighting the complex risks of micro-nanoplastics in agricultural ecosystems and their cultivar-dependent impacts.