Effects of polyethylene microplastics on seed germination, growth performance, biomass production and physiological function of cowpea (Vigna unguiculata) young seedlings

Microplastics (MPs) in terrestrial ecosystems have recently raised concerns; here, we performed a pot experiment and investigated the growth and development by different doses of polyethylene microplastics (PE MPs) in a net house under natural conditions and tested the effects of PE MPs on seed germination, growth performance, physiological function and biomass production of cowpea (Vigna unguiculata) for 25 days. According to the hypothesis, a significant dose-dependent inhibition of cowpea seedling's growth and development was observed depicting the phytotoxicity of PE MPs. Results indicate that high concentrations of PE MPs have antagonistic effects on the growth of plant such as plant height, leaf length and root length within a short period of time. Plants grown in PE MPs show less nutritional characters and exhibit a significant drop in leghemoglobin content as the concentration of MP increases which is one of the novel findings. The results showed a significantly increased antioxidant enzyme activity indicating the stress condition of plants due to exposure to PE MPs. PE MPs undergo initial stage of partial disintegration when it contacts with soil which were detected through SEM analysis when compared to control. Comprehensive field study involving MPs at different concentrations throughout the cowpea's whole life cycle until harvest is needed to better clarify the effects of PE MPs and produce reliable results.