Abstract: The extensive use of plastics has led to the widespread presence of microplastics (MPs) in agricultural soils, which are emerging pollutants with a significant impact on crop growth and development. This study aims to analyze the effects of different concentrations and types of MPs on the growth of maize seedlings. There were two types of MPs with a particle size of 0.15 mm, polyethylene (PE) and polyvinyl chloride (PVC), and three exposure concentrations \[0 (CK), 0.5%, and 5%\]. Height, leaf area, leaf SPAD value, dry matter accumulation, and root morphology of maize seedling under different MPs treatments were analyzed. The results showed that the growth of maize seedlings was mainly influenced by MPs concentration instead of MPs type. Compared with that in the CK, plant height, leaf area, aboveground biomass, and root biomass showed an increasing trend under 5% MPs treatment, but a decreasing trend under 0.5% MPs treatment. Compared with that in the CK, plant height, leaf area, and SPAD value were significantly reduced under 0.5% PVC MPs treatment (P<0.05). Conversely, leaf and aboveground biomass were significantly increased under 5% PE MPs treatment (P<0.05), and leaf, stem, aboveground biomass, and belowground biomass were significantly increased under 5% PVC MPs treatment (P<0.05). The 5% MPs treatment significantly increased root length, root volume, and root surface area by 55.1%-162.5%, 53.3%-86.9%, and 106.8%-127.7%, respectively, while 0.5% MPs had no significant effect on root variables. Overall, a 5% concentration of MPs enhanced the plant health index of maize seedlings, with no significant differences in various growth indicators between PVC and PE under the same concentration of MPs. Principal component analysis revealed that the traits of maize seedlings treated with 5% PE-MPs and 5% PVC-MPs were mainly driven by aboveground biomass, leaf dry weight, total biomass, root surface area, and root volume, while the traits of maize seedlings treated with 0.5% PE-MPs and 0.5% PVC-MPs were driven by root/shoot ratio. In summary, the concentration of MPs, rather than their type, significantly affects the growth of maize seedlings, exhibiting a general trend of “inhibition under low concentration and promotion under high concentration”.

Key words: polyethylene, polyvinyl chloride, plant health index, root morphology