Nanoparticles alter the nature and strength of intraploidy and interploidy interactions in plants

Engineered nanoparticles have profound impacts on organisms, yet there is limited understanding of how nanoparticle exposure shapes species interactions that are key for natural community dynamics. By growing plants of the same (intraploidy) and different ploidy levels (interploidy) of Fragaria in axenic microcosms, we examined the influence of nanoparticles on species interactions in polyploid and diploid plants. We found that, under copper oxide (CuO) nanoparticle exposure, polyploids experienced reduced competition when growing with polyploids (the effect of polyploids on polyploids, RII8x,8x), and a shift towards facilitation when growing with diploids (the effect of diploids on polyploids, RII8x,2x). This reduction in competitive interactions in polyploids, in line with the stress gradient hypothesis, was primarily caused by nanoscale effects, because the strength of competitive interactions (RII8x,8x and RII8x,2x) remained relatively unchanged under CuO bulk particles compared to control conditions. In contrast, diploids experienced a shift from facilitation (RII2x,2x and RII2x,8x) under control conditions to neutrality under CuO nanoparticles, with a similar reduction in facilitation observed with both nanoparticles and bulk particles. These findings underscore ploidy specific interaction dynamics and the need of considering species interactions when predicting organismal responses to nanoparticle pollution in ecological communities. ### Competing Interest Statement The authors have declared no competing interest.