Unveiling the Effects of Polypropylene Microplastics (PP-MPs) on Growth Attributes and Antioxidant Defense System in Wheat (Triticum aestivum L.)

Abstract Microplastics (MPs), as emerging pollutants in soil ecosystems, are increasingly alarming and present severe environmental threats to crop plants. Despite the elevated pollution of MPs in terrestrial ecosystems, the impact of polypropylene microplastics (PP-MPs) on plant growth and physiology has not been clearly elucidated. Therefore, this study aimed to reveal the effects of different levels of polypropylene microplastics (0.05%, 0.1%, 0.5%, and 1% PP-MPs) on wheat, one of the world's foremost crops. While 0.05% PP microplastic did not affect plant growth, 0.1%, 0.5%, and 1% PP microplastic pollution resulted in inhibition of shoot and root growth attributes. Stunted plant growth was accompanied by oxidative stress, as indicated by increased malondialdehyde (MDA) and hydrogen peroxide (H 2 O 2 ) content in this study. Higher levels of PP-MPs (0.5% and 1% PP) notably reduced photosynthetic pigment contents (chlorophyll a , chlorophyll b , total chlorophyll, and carotenoid) and total protein amount. Furthermore, exposure to higher concentrations of PP-MPs induced an increase in proline content, superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) activities to reduce the harmful effects of oxidative stress. The overall pattern of this study demonstrated that 0.05% PP-MPs had no adverse effect on wheat, but higher PP-MP contamination led to detrimental effects. These findings encourage addressing issues associated with microplastic pollution in crop plants and ultimately highlight the importance of plastic waste management for sustainable agriculture in soils.