Microplastic and Nanoplastic Interactions with Plant Species: Trends, Meta-Analysis, and Perspectives

The ubiquitous presence of nanoplastics (NPx) and microplastics (MPx) in the environment has been demonstrated, and as such, the exposure scenarios, mechanisms of plant response, and ultimate risk must be determined. Here, we performed a meta-analysis of the most recent literature investigating the effect of MPx/NPx on plant species under laboratory and field conditions so as to evaluate the current state of knowledge. Effects of MPx/NPx exposure in plants vary as a function of plant species, and interestingly, nonsignificant responses are reported in staple crops. We found that NPx (<100 nm) more negatively affected plant development parameters, photosynthetic pigments, and biochemical indicators than did MPx (>100 nm). Surprisingly, NPx exposure exhibited negligible effects on germination rate, although root morphology was negatively affected. Alternatively, MPx negatively affected (14%) germination and generally exhibited nonsignificant effects on root morphology. The effect of MPx/ NPx on plant health decreases with increasing exposure time. No specific trends were evident for the production of biochemical enzymes as related to MPx/NPx concentration or size. Furthermore, we provided a framework for additional investigative work to address the knowledge gaps and to enable accurate assessment of the fate and risk of these materials to environmental and human health.