Response strategies of stem/leaves endophyte communities to nano-plastics regulate growth performance of submerged macrophytes

Research on the toxicity effects of nano-plastics on submerged macrophytes has been increasing over the past several years. However, how the endophytic bacteria of submerged macrophytes respond to nano-plastics remains unknown, although they have been widely shown to help terrestrial plants cope with various environmental stressors. Here, a microcosm experiment was performed to unravel the effects of high concentration of nano-plastics (20 mg/L) on three submerged macrophyte (Vallisneria natans, Potamogeton maackianus, Myriophyllum spicatum) and their endophytic bacterial communities. Results indicated that nano-plastics induced antioxidative stress in plants, but significantly reduction in relative growth rate (RGR) only occurred in V. natans (from 0.0034 to -0.0029 day ), accompanied by change in the stem/leaves endophyte community composition. Further analysis suggested nano-plastics caused a reduction in environmental nutrient availability and the proportion of positive interactions between endophyte communities (43%), resulting in the lowest RGR of V. natans. In contrast, endophytes may help P. maackianus and M. spicatum cope with nano-plastic stress by increasing the proportion of positive correlations among communities (70% and 75%), leaving their RGR unaffected. Collectively, our study elucidates the species-specific response strategies of submerged macrophyte-endophyte to nano-plastics, which helps to reveal the different phytoremediation potential of submerged macrophytes against nano-plastic pollution.