Microplastics change the safe production ability of arsenic-stressed rice (Oryza sativa L.) by regulating the antioxidant capacity, arsenic absorption, and distribution in rice

Abstract

Microplastics (MPs) and arsenic (As) are pervasive pollutants in agricultural soils, drawing increasing attention due to their combined toxicity. While biodegradable plastics offer a potential alternative to conventional plastics, their interactions with As and subsequent effects on edible crops remain largely unexplored. Here, we investigated the combined effect of polyethylene (PE) and polylactic acid (PLA) microplastics with As on rice growth, As accumulation, and rhizosphere microbial communities in two rice genotypes. The results showed that As-PE exposure was more detrimental to rice growth than As alone, leading to biomass reductions of 21.1–39.8% in 2A roots, 32.6–54.6% in stems, and 21.9–32.7% in leaves. In contrast, PLA mitigated As-induced growth inhibition in 2119, increasing leaf biomass by 56.1–71.9% and stem biomass by 45.6–57.9%. The presence of MPs intensified As toxicity and induced oxidative stress, with the low-As-accumulating genotype exhibiting stronger detoxification mechanisms, including enhanced sequestration of As in the leaf cell wall and MPs facilitated As adsorption and desorption in the root zone, exacerbating As accumulation in the aerial part of rice, particularly during grain filling. Different degradation characteristics of MPs altered microbial composition and function, impacting rhizosphere iron plaque formation and As availability in soil. PLA decreased the As content in 2A and 2119 roots by 6.1% and 24.0%, respectively, whereas PE increased by 10.6% and 12.9%. This study provides new insights into the comprehensive toxicity of As and MPs in the soil-plant system, highlighting their effects on As uptake and accumulation in rice.