Microplastics as emerging stressors in plants: biochemical and metabolic responses

Plastics have become an integral part of modern life, driving global production to a new level and contributing to widespread environmental pollution due to inadequate recycling and waste management systems. The COVID-19 pandemic exacerbated this crisis by increasing the use of single-use plastics, countering earlier attempts to reduce plastic use. A critical concern with plastic pollution is its progressive degradation into microplastics (MPs) and nanoplastics (NPs), which can disperse through air, water, and soil and reach every part of ecosystems. The application of sewage sludge, the breakdown of plastic mulch, and wastewater irrigation have made agricultural soils into important MP sinks, with grave consequences for soil health and food safety. MPs and NPs in particular present significant concerns because of their tiny size, high mobility, and capacity to interact with pollutants in the soil, enter plant tissues, and interfere with metabolic, physiological, and biochemical processes. Recent studies have highlighted their uptake in diverse crops, demonstrating oxidative stress, impaired growth, and significant metabolic reprogramming. This review critically examines the pathways of microplastic uptake and transport in plants, resulting in physiological and biochemical alterations, and the underlying metabolic responses. Microplastics are found to interfere with soil microbes and nutrient cycling, as well as plant metabolism. It is essential to comprehend these changes using multi-omics techniques in order to create resilient crops and successful mitigation plans. By identifying current knowledge gaps, it outlines future research directions to deepen our understanding of plant-microplastic interactions and their broader consequences for agriculture and ecosystem sustainability.