Effects of Polyethylene Microplastics on Seed Germination, Seedling Growth, and Physiological Characteristics of Maize

Microplastics (MPs), widely present in soil environments, pose an increasingly potential threat to soil ecological health and agricultural production safety. This study systematically evaluated the effects of irregular polyethylene (PE) microplastics at different particle sizes (28 μm, 87 μm) and concentrations (0, 200, and 1000 mg/L) on maize seed germination and seedling growth through germination tests and hydroponic experiments. The results indicated that seed germination was less influenced by particle size but more significantly affected by concentration. In particular, under high concentration and large particle size PE treatments, germination rate, germination potential, germination index, and seed vigor index decreased by 13.08%, 24.14%, 23.02%, and 59.57%, respectively, compared to the control group. Both PE particle size, concentration, and their interaction significantly influenced maize seedling growth. The inhibition rates of stem length, shoot biomass, and root biomass ranged from 0% to 34.36%, 9.25% to 18.74%, and − 30.07% to − 24.1%, respectively. Meanwhile, the photosynthetic pigment content in leaves was also significantly affected, with chlorophyll a and chlorophyll b contents decreasing by 6.4~25.5% and 8.5~24.5%, respectively, while carotenoid content increased markedly by 30.4% to 78.4%. In addition, PE exposure induced an oxidative stress response, characterized by a 36.4~81.8% decrease in root activity and a 4~552.5% increase in malondialdehyde (MDA) content. In summary, polyethylene microplastics adversely affect maize seed germination, seedling growth, and physiological characteristics, with these effects being regulated by both particle size and concentration.