[Physiological and Ecological Response Characteristics and Transcriptomic Change Characteristics of Rice （Oryza sativa）Under Different Microplastic Stresses].

Abstract

Traditional plastics are difficult to degrade in the environment after use and disposal, but they are prone to aging and forming microplastics （MPs）, which are emerging environmental contaminants, posing a serious threat to global ecological security and human health. To mitigate the ecological impact caused by traditional plastic products, the use of biodegradable plastics is gaining widespread attention. However, the ecological risks of biodegradable materials to the soil remain unclear. Furthermore, biodegradable plastics are highly susceptible to aging behaviors such as pyrolysis, weathering, and exposure to light in the environment and turn into smaller MPs. To reduce the pollution problems caused by the disposal of traditional plastics, biodegradable plastics have been continuously developed and are increasingly utilized, garnering considerable attention. However, degradable plastics are susceptible to degradation through aging in the environment after use, yet there has been limited reporting on the impact of degradable plastics on ecosystems post-aging and degradation. Additionally, the risks to the ecosystem after the aging of degradable plastics are not very clear. To further elucidate the ecological effects of different MPs on plants, rice （Oryz sativa） was taken as the research subject in this study. Fresh degradable polylactic acid MPs （PLA-MPs, PLA）, aged-degradable polylactic acid MPs （aged-PLA-MPs, APLA）, and traditional polyethylene MPs were also selected to study the physiological and ecological response characteristics and transcriptomic change characteristics of rice under different MP stresses. The results indicated that rice exhibited varying ecological responses to different MP stresses, and PLA and APLA induced more severe oxidative stress in rice compared to PE-MPs. Compared with that of the CK group, the rice SOD contents of the PE treatment groups and aged PLA-MPs treatment groups were significantly increased by 17.41% and 36.48%, respectively. The rice POD contents of the PE and PLA groups were significantly increased by 21.91% and 48.65%, respectively. The CAT levels in the PLA and APLA groups were significantly increased by 29.34% and 24.91%, respectively. The MDA contents in the PLA and APLA groups were significantly increased by 70.52% and 135.94%, respectively. Under the stress of different MP exposure, significant changes were observed in chlorophyll and chlorophyll fluorescence parameters in rice. The chlorophyll contents in the rice were significantly reduced by 21.28% and 12.77% in the PLA group and aged PLA-MPs, respectively. The maximum optical quantum yield （F_v/F_m） was significantly reduced by 13.95% and 44.19%, respectively. Non-photochemical fluorescence quenching （NPQ_Lss） significantly increased by 222.64% and 143.40%, respectively. Transcriptome sequencing analysis showed that exposure to MPs led to enrichment of tetrapyrrole binding, heme binding, oxidoreductase, iron ion binding, and phenylpropanoid biosynthesis pathways in rice. The aged PLA-MPs group of rice was more concentrated in the enrichment of hydrolases and amino acid metabolism and biosynthesis pathways. The results of this study have practical and guiding significance for the comprehensive evaluation of the potential ecological risks of degradable MPs in the environment and their ecological effects on plants.