Effects of polyethylene and polylactic acid microplastics on plant growth and bacterial community in the soil

Area of Science:

• Environmental Science
• Soil Science
• Plant Biology

Background:

• Microplastics (MPs) are pervasive environmental contaminants.
• Biodegradable MPs (BMPs) are increasingly used, but their ecological impact is poorly understood.
• Differential effects of MPs based on biodegradability on soil-plant systems require investigation.

Purpose of the Study:

• To investigate the effects of polyethylene MPs (PEMPs) and polylactic acid MPs (PLAMPs) on soybean (Glycine max) physio-biochemical performance and soil bacterial communities.
• To compare the impacts of MPs with different biodegradability on terrestrial ecosystems.
• To elucidate the specific effects of BMPs on soil-plant interactions.

Main Methods:

• Soybean plants were exposed to PEMPs and PLAMPs.
• Physio-biochemical parameters (e.g., root length, enzyme activity) were measured.
• Metabolomic profiling and soil bacterial community analysis (Shannon and Simpson indices, dinitrogen fixation bacteria) were performed.

Main Results:

• PEMPs did not exhibit significant toxicity to soybean growth.
• 0.1% PLAMPs significantly reduced soybean root length by 27.53%.
• MP exposure altered peroxidase (POD) and catalase (CAT) activity in soybean leaves, affected amino acid metabolism, and modified soil bacterial diversity and dinitrogen fixation under PLAMPs.

Conclusions:

• Biodegradable MPs, specifically PLAMPs, can negatively affect soybean growth and soil microbial communities.
• The biodegradability of MPs is a critical factor determining their environmental impact.
• BMPs may pose a more significant threat to terrestrial ecosystems than conventional MPs, warranting further research.