Responses of plants and rhizosphere microorganisms in constructed wetlands under sulfamethoxazole stress

In order to explore the response mechanism of plants and rhizosphere microorganisms in constructed wetlands under the stress of sulfamethoxazole (SMX), the removal efficiency of different concentrations of SMX in the combined remediation of five plants and rhizosphere microorganisms was characterized. According to the removal efficiency of SMX, the root activity, reactive oxygen species and antioxidant system of Gladiolus hybridus and Cyperus alternifolius were studied, and the response characteristics of their rhizosphere microbial community under SMX and temperature stress were analyzed simultaneously. The results showed that the removal rates of SMX by Gladiolus hybridus and Cyperus alternifolius were the highest in the five constructed wetland plants and rhizosphere microorganisms, with an average of 40.38% and 44.70%, respectively. When SMX concentration was higher than 30 mg/L, the root activity of Gladiolus hybridus and Cyperus alternifolius was inhibited, which was 69.77% and 67.26% lower than that of 0 mg/L, respectively. With the increase of SMX concentration, the reactive oxygen species (ROS) content of Gladiolus hybridus and Cyperus alternifolius increased by 69.08% and 72.67% compared with 0 mg/L, respectively, but the antioxidant enzyme activities decreased by 19.32% and 24.83%, respectively. Compared with normal temperature (20-25 ℃), the ROS content of Gladiolus hybridus and Cyperus alternifolius increased by 2.26% and 1.98%, and the antioxidant enzyme activity decreased by 47.72% and 44.42%, respectively, under low temperature (4-12 ℃). The measurement results of the rhizosphere microbial community by high-throughput sequencing technology showed that high concentrations of SMX inhibited the diversity and species richness of the plant rhizosphere microbial community. PICRUSt function prediction software was used to predict the microbial community function, and it was found that the relative abundance of microbes with amino acid and carbohydrate metabolism was higher.