Absorption and Transport of Different ZnO Nanoparticles Sizes in Agrostis stolonifera: Impacts on Physiological, Biochemical Responses, Root Exudation, and Microbial Community Structure

Abstract

Nanomaterials play a crucial role in various applications, but their environmental impact necessitates effective recycling strategies. This study investigates the effects of different ZnO nanoparticles (ZnO-NPs) sizes (0, 30, 50, and 90 nm) on Agrostis stolonifera, focusing on physiological and biochemical responses, root exudate, and microbial community structure. The results showed that the most optimal physiological and biochemical responses, including enhanced plant growth and increased activities of superoxide dismutase, peroxidase, and catalase, were observed at 50 nm ZnO-NPs. Agrostis stolonifera accumulated more ZnO-NPs at 30 nm, with Zn content in root and leaf tissues reaching 186 mg/kg and 294 mg/kg, respectively. Meanwhile, SEM-Mapping and TEM analyses confirmed the absorption and transport of ZnO-NPs within Agrostis stolonifera. Furthermore, root exudates analysis revealed an increase in the types of organic matter secreted by roots at 30 nm and 50 nm ZnO-NPs, while 90 nm ZnO-NPs had the opposite effect. 16S rRNA gene sequencing showed that the species diversity and uniformity of root microorganisms exhibited contrasting trends with increasing ZnO-NPs size, with roots exposed to 50 nm ZnO-NPs showed higher species richness than those exposed to 30 nm or 90 nm. However, beneficial microorganisms such as Bryobacter and Methylophilus were inhibited by 90 nm ZnO-NPs. This study provides novel insights into a potential ZnO-NPs recycling strategy in soil using Agrostis stolonifera, offering a means to mitigate nanoparticle-induced damage to soil and crops.