An in vitro phytotoxicity assessment of UV-enhanced biodegradation of plastics for spinach cultivation

Abstract

Polyethylene-based plastic mulch films are widely utilized in agriculture due to their benefits in improving soil conditions and crop yield. However, their degradation into microplastics has been shown to negatively impact plant growth and development, posing a significant source of plastic pollution in the agroecosystem. In response to this issue, the present study aimed to design an innovative bioremediation system based on PGPR (Pseudomonas aeruginosa), biochar, and UV treatment for the degradation of plastics. Additionally, the phytotoxic effects of plastic residues on the growth of Spinacia oleracea (spinach) were evaluated to understand the impact of plastic contamination on plant health. Bacterial strains were isolated from vegetable-cultivated soil with plastic mulch. The bacterial strain demonstrating the most effective plant growth-promoting properties and plastic degradation efficiency was identified as Pseudomonas aeruginosa (OP007126). Biochar was prepared from food waste and thoroughly characterized. Polyethylene (PE) was exposed to UV radiation to induce degradation. A glass house experiment was then designed to assess the effect of PGPR, biochar, and UV radiation on mitigating plastic-induced stress and promoting plant growth. Fourier transform infrared spectroscopy (FTIR) and weight loss measurement showed a maximum degradation of 62% with a combination of all treatments. PE negatively affected the morphology of the plant as it decreased the shoot and root fresh weight by up to 60%. Biochemical parameters of spinach were also affected by PE, as proline content increased by up to 45%. The use of amendments demonstrated effectiveness in alleviating the detrimental impact of PE on spinach plants, as evidenced by improvements in morphological, physiologic, and biochemical parameters. This approach presents a promising strategy to mitigate the detrimental effects of plastic mulch and warrants further investigation through field trials.

Graphical abstract

Keywords

Microplastics / Biochar / Degradation / PGPR / UV

Highlight

	● PGPR, Plant growth promoting rhizobacteria was identified as Pseudomonas aeruginosa .
	● Pseudomonas aeruginosa was used to degrade plastic and to enhance plant growth.
	● Biochar was proven as good soil amendment for degradation of microplastic (MPs).
	● P. aeruginosa , biochar and UV rays enhanced plastic degradation and Spinacea oleracea growth.

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