The tolerance mechanism and accumulation characteristics of Phragmites australis to sulfamethoxazole and ofloxacin

Antibiotic pollution has become a hot issue worldwide, which has toxic effects on plants and even threatens human health. As a common wetland plant, the tolerance mechanism of Phragmites australis to antibiotics is rarely reported. In this study, we investigated the enrichment characteristics and biological response of P. australis to sulfamethoxazole (SMZ) and ofloxacin (OFL) residues, which are common in the environment. We found that the simulated concentration of antibiotics far exceeded the current level of antibiotic residues in the water environment, but it did not significantly inhibit the growth of P. australis. At 1 mg L-1, OFL and SMZ significantly increased the biomass of P. australis, which was mainly related to the improvement of root activity and photosynthetic efficiency, but the duplex treatment (SMZ + OFL) did not significantly stimulate the growth of reeds. OFL could significantly reduce the accumulation of reactive oxygen species (ROS) in P. australis. When OFL was 1 mg L-1, compared with control, superoxide anion and H2O2 were reduced by 11.19% and 10.76%, respectively, which was mainly related to the improvement of membrane stability. SMZ and SMZ + OFL had no significant effect on ROS, but they significantly increased antioxidant enzyme activity. SMZ and OFL could increase soil invertase, urease, and protease activities, and the tested antibiotics had no significant effect on the Shannon-Wiener index of soil microorganisms. The accumulation of antibiotics within tissues could be ranked as root > leaf > stem, and the accumulation and transport of OFL were higher than those of SMZ.