Biodegradable microplastics affect tomato (Solanum lycopersicum L.) growth by interfering rhizosphere key phylotypes

Biodegradable microplastics (BMPs), which form as biodegradable plastics degrade in agricultural settings, may influence plant growth and soil health. This study investigates the effects of BMPs on tomato growth and the microbial mechanisms involved. A greenhouse experiment applied BMPs-polyhydroxyalkanoate (PHA), polylactic acid (PLA), poly(butylene succinate-co-butylene adipate) (PBSA), and poly(butylene-adipate-co-terephthalate) (PBAT)-to tomato plants. The study analyzed their effects on plant growth, soil properties, and rhizosphere microbial communities. BMP treatments significantly reduced tomato biomass, height, and chlorophyll content compared to the control. PLA0.1 decreased the chlorophyll a/b ratio, while PLA1 increased it. Elemental analysis showed PLA1 increased phosphorus, calcium, and potassium in leaves, whereas all BMPs reduced nitrogen levels. BMPs also altered soil nitrogen and DOC levels, significantly shifting rhizosphere microbial communities, with a notable increase in Betaproteobacteria abundance. Ecological network analysis revealed that BMPs disrupted key microbial modules linked to plant growth. Beneficial modules positively associated with biomass and nutrient uptake were reduced under BMP treatments, whereas harmful microbial taxa in module 3, associated to poor plant health, were promoted. These shifts suggest that BMPs disrupt microbial ecological relationships critical for optimal plant growth. The findings highlight the potential negative impacts of BMPs on tomato growth through changes in microbial dynamics and soil properties.