Phytotoxic Effects of Polystyrene and Polymethyl Methacrylate Microplastics on Allium cepa Roots

Abstract

Plastic contamination has become one of the most pressing environmental issues due to rapidly increasing production of disposable plastic products, their fragmentation into smaller pieces, and long persistence in the environment, which affects all living organisms, including plants. In this study, Allium cepa roots were exposed to 0.01, 0.1, and 1 g L−1 of commercial polystyrene (PS-MPs) and polymethyl methacrylate microparticles (PMMA-MPs) for 72 h. Dynamic light scattering (DLS) analyses showed high stability of both types of MPs in ultrapure water used for A. cepa treatment. Morphometric analysis revealed no significant change in root length compared to control. Pyrolysis hyphenated to gas chromatography and mass spectrometry (Py-GC-MS) has proven PS-MPs uptake by onion roots in all treatments, while PMMA-MPs were recorded only upon exposure to the highest concentration. Neither MPs induced any (cyto)toxic effect on root growth and PMMA-MPs even had a stimulating effect on root growth. ROS production as well as lipid and protein oxidation were somewhat higher in PS-MP treatments compared to the corresponding concentrations of PMMA-MP, while neither of the applied MPs induced significant damage to the DNA molecule assayed with a Comet test. Significantly elevated activity of H2O2 scavenging enzymes, catalase, and peroxidases was measured after exposure to both types of MPs. Obtained results suggest that onion roots take up PS-MPs more readily in comparison to PMMA-MPs, while both types of MPs induce a successful activation of antioxidant machinery in root cells that prevented the occurrence of toxic effects.

Impacts of Plastics on Plant Development: Recent Advances and Future Research Directions

“…These studies have demonstrated that PS had a more negative effect on root growth in mung beans compared to onions. Biba et al [ 63 ] reported that there were no significant changes in onion root growth after exposure to any of the tested PS MP concentrations, compared to the control, although the highest concentration (1 g/L) caused a slight decrease in length. On the other hand, Chen et al [ 64 ] found that any applied concentration of PS MPs significantly reduced the growth characteristics of mung bean plants, including the shoot and root growth.…”

Microplastic stress in plants: effects on plant growth and their remediations

“…(2021b) . Nonetheless, Biba et al. (2023) observed no drastic changes in O 2 - production in onion roots under different PS MP stress levels; however, when compared with the effects of PMMA MPs, PS MP treatment showed relevantly higher O 2 - production, thereby indicating MP-type response of ROS production in the root.…”

Microplastics exposure altered hematological and lipid profiles as well as liver and kidney function parameters in albino rats (Rattus norvegicus)

“…While some of these plastics end up in terrestrial environments, the majority find their way into aquatic ecosystems. These plastics undergo photodegradation, transforming into microplastics (classified as secondary microplastics), accumulating in the soil [ 7 ], water and sediment [ 8 ], and terrestrial and aquatic organisms [ 9 ]. Additionally, certain microplastics classified as primary microplastics are intentionally produced for various products like textiles, cosmetics, and fishing nets, entering the environment or human bodies [ 8 ].…”