Unveiling the effect of microplastics on agricultural crops – a review

Microplastics (MPs), ever since they were identified as a potential and widely distributed persistent contaminant, the number of studies highlighting their impacts on various terrestrial ecosystems have been increasing. Recently, the effect of MPs on the agricultural ecosystem has gained momentum. Hence, the present review examines the impact of microplastics on agricultural crop systems and the mechanism underlying its toxicity. The current review revealed that most of the studies were conducted at a laboratory scale and under controlled conditions. Additionally, it was observed that polystyrene (PS) followed by polyethylene (PE) are the most studied polymer type, while the most studied plants are wheat and maize. Hitherto, literature studies suggest that the microplastics’ influence on plant growth can be negative or sometimes neutral; while in some cases it exerts a hormetic effect which depends on other factors determining plant growth. Notably, the main mechanisms through which microplastics influence plant growth are mechanical damage, alteration of soil properties, or by leaching of additives. Overall, with burgeoning research interest in this aspect, the current review has significant implications for the toxicity of MPs on plants and throws light on the need to develop novel guidelines toward the sustainable use of plastics in agricultural sector. However, realistic field-level studies and estimating the MPs concentration at various region are essential to develop remediation approaches. Future studies should also focus on translocation and accumulation of micron sized MPs in edible portion of crops and their effect on food safety. Although several papers on various elements of microplastics in terrestrial ecosystems have recently been published, there is currently no comprehensive review focusing on the effect of microplastic contamination in plants. Furthermore, no review has conducted a meta – analysis indicating the most commonly reported source, methods to identify the MPs in plants, majorly reported polymer type, widely studied plant species and the mechanism underlying in its toxicity. Hence, this review mainly focuses on edible/economically important crops and highlights the impacts of microplastics on different plant parameters i.e., seed germination, root and shoot growth, photosynthesis, nutrient metabolism, oxidative damage and genotoxicity and mechanisms through which microplastics affect plant growth.