Growth and physiological–biochemical characteristics of cucumber (Cucumis sativus L.) in the presence of different microplastics.

Research on the impact of microplastics on crops has gradually attracted wide attention, but most of the current research focuses on the impact of nano-microplastics on crops by hydroponics. To make the impact of soil microplastics on crop growth more consistent with the natural state, we selected three types of microplastics (polyvinyl chloride (PVC), polyethylene (PE), and polystyrene (PS), with particle sizes smaller than 13 μm) present in agricultural soil and treated cucumber plants with two microplastic concentrations (0.05 g kg⁻¹ and 0.5 g kg⁻¹). Using the soil culture method, we investigated the influence of microplastics on the growth and physiological and biochemical characteristics of cucumber. The results showed that both concentrations of PVC, PE, and PS resulted in reduced fresh and dry weights of the underground parts of the cucumber and significantly promoted their absorption of the mineral element Zn. However, there were no significant effects on the fluorescence origin (F₀) and the dissipated light energy of the PS unit reaction center (DI₀/RC). Both concentrations of PVC suppressed the gene expression of the four antioxidant enzymes (SOD, POD, CAT, and APX). PVC and PS significantly increased the contents of chlorophyll a, chlorophyll b, and carotenoids. Our study confirmed that the decrease in net photosynthetic efficiency (P_n) of cucumber leaves is caused by the decrease in water use efficiency (WUE) caused by the increase in the transpiration rate (T_r) of cucumber plants. Our results provide new insights into the impact of farmland microplastics on crop growth and development and set the foundation for further research. [ABSTRACT FROM AUTHOR]