Moderate Application of Selenium Alleviates the Stress of High Concentration Polypropylene Nanoplastics on Alfalfa

SUN Ping; ZHENG Xinmiao; ZHU Wenyan; GUO Zirui; LI Jie; XU Shixiao

doi:10.15926/j.cnki.issn1672-6871.2025.06.009

Abstract：This study aims to explore the regulatory mechanism and repair effect of selenium on the physiological response of alfalfa(Medicago sativa)under the stress of polypropylene nanoplastic.It provides a theoretical basis for the phytoremediation of microplastic-contaminated soil.A pot experiment was conducted.An interaction model was constructed with PP-NPs(100 nm,1%)and soil selenium mass ratio gradients(0,0.4,0.8,1.2,1.6 mg·kg-1).The responses of growth indices,chlorophyll content,photosynthetic parameters,nutritional quality,and root parameters of alfalfa(75 d growth cycle)were systematically evaluated.The results show that the addition of PP-NPs significantly inhibits the plant height,aboveground biomass,net photosynthetic rate,stomatal conductance,and contents of chlorophyll a and chlorophyll b of alfalfa(P<0.05),which are decreased by 9.8%,3.3%,35.4%,49.5%,11.3%,and 10.7%,respectively.The addition of selenium can alleviate the toxic effects of PP-NPs and significantly increase the net photosynthetic rate and chlorophyll content of alfalfa(P<0.05).A membership function evaluation system based on principal component analysis is established using 5 indicators,including aboveground biomass,dry matter content,crude protein content,acid detergent fiber content,and neutral detergent fiber content.It is quantitatively concluded that the 1.2 mg·kg-1 selenium treatment performed best in comprehensive indicators.The results of the study show that selenium improves the stress resistance and productivity of alfalfa under PP-NPs pollution through photosynthetic gain and root architecture remodeling.This provides a new technical pathway for high-quality forage production in microplastic-contaminated agricultural areas.