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The hidden constrains in soil ecology and plant physiology: microplastic effects on nutrient and metal transport in soil-plant continuum
Summary
Researchers grew lettuce in soils amended with conventional polyethylene and biodegradable microplastics, finding both types significantly reduced soil nutrients and plant growth, while also triggering upregulation of metal transporter genes — indicating microplastics act as stressors that alter how plants absorb and move elements.
Plastic pollution, particularly microplastics (MPs), is a growing ecological concern. In agroecosystems, plastic mulches enhance crop production but, alter nutrient cycles, affect soil structure and aeration, and may disrupt to soil-plant interactions and human health. The research, through a multifaceted and ecological approach, aimed to investigate: i) the interaction between microplastics and element translocation from soil to plants; ii) plant morphological, biochemical, and physiological responses to MPs-contaminated soils; iii) differential effects of conventional (PE) and biodegradable (BPs) MPs on soil and plants. Lettuce was grown in soils amended with 1% and 2% PE or BPs. At harvest, soil properties, nutrient status, heavy metals concentrations were analysed. Plant biometry, photosynthesis, bioaccumulation, translocation, and metal transporter gene expression were evaluated. Untreated soils served as controls. The addition of 2% of PE and BP significantly (p < 0.001) reduced soil nutrients: nitrate (−7.5%; −15.5%), nitrite (−65.4%; −46.5%), and sulphate (−13.9%; −31%, respectively). In 2%BPs treated-leaves, Zn (−96%), K (−39%), and Mg (−33%) significantly (p < 0.001) decreased as well as in plant growth (−67%) and photosynthesis (−24%) were reduced. Metal-transporter expression was significantly (p < 0.05) upregulated in 2%PE-treated roots (NRAMP5:+21.4, ZIP:+7.74, IRT1:+2.21, HMA3:+2.64) and leaves (IRT1:+3.2-fold), and 2%BPs-treated roots showed NRAMP5 (+18.2), ZIP (+5.81), and IRT1 (+2.13) upregulation. BPs constrained plant growth and both MPs types triggered a molecular response. MPs’ presence in soils can be considered a stressor for plants as the consequent changes in element availability in soils caused alterations of bioaccumulation and translocation indices and upregulation of metal transporter genes.