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Effects of Polyethylene and Polystyrene Microplastics on Oat (Avena sativa L.) Growth and Physiological Characteristics
Summary
Researchers conducted pot experiments exposing oat seedlings to polyethylene and polystyrene microplastics at four concentrations and measured effects on growth and physiological parameters. Both particle types reduced shoot and root biomass in a dose-dependent manner, with polystyrene microplastics causing greater physiological disruption, particularly to chlorophyll content and antioxidant enzyme activity.
Despite increasing environmental concerns, there are few studies on the potential effects of polyethylene and polystyrene microplastics on feed crops. The effects of polyethylene (PE) and polystyrene (PS) microplastics with a diameter of 2 μm at different concentrations (0.1%, 0.5%, 1%, and 5%) (w/w) on the growth and development of oats were analyzed in a pot experiment, with no microplastics added as the Control (Ctrl) group. The results showed that PS microplastics exhibited a spherical morphology, whereas PE microplastics displayed an irregular morphology. PE microplastics had an inhibitory effect on oat growth, chlorophyll content, photosynthetic parameters and antioxidant enzyme activity, and this effect was concentration-dependent; specifically, the inhibitory intensity increased progressively as the concentration of PE microplastics rose. In contrast, treatments involving varying concentrations of PS microplastics elicited distinct effects on the physiological and biochemical parameters of oats. The 0.1% PS microplastics treatment significantly enhanced the net photosynthetic rate of oat leaves (by 14.0%), while the 5% PS microplastics treatment significantly reduced the seedling height (by 31.1%), the total chlorophyll content (by 34.6%), the transpiration rate (by 35.7%), the stomatal conductance (by 71.1%), and the intercellular CO2 concentration (by 43.1%). Furthermore, a significant decrease in antioxidant enzyme activity was observed in oats after the 5% PE microplastics treatment. The activities of peroxidase (POD), catalase (CAT) and superoxide dismutase (SOD) decreased by 17.1%, 89.2% and 5.6%, respectively. At the same concentration (5%), PE microplastics exhibited a more pronounced inhibitory effect on oats compared to PS microplastics. In summary, this study demonstrates that microplastics impair photosynthesis and antioxidant capacity in oats, thereby inhibiting their normal growth and development. These findings provide a theoretical foundation and supporting data for further research into the toxicity of microplastics to oats.