[Tolerance Screening and Critical Response Mechanisms of Wetland Plants to Sulfonamide Antibiotics]

Antibiotic contamination in aquacultural wastewater challenges constructed wetland efficacy， necessitating the identification of highly tolerant wetland plant species. Ten dominant wetland plant species in South China were exposed to sulfonamide antibiotics （SAs） at concentrations of 50-5 000 μg·L^-1. Growth-morphological adaptations （root number， length， biomass， etc.） and physiological-biochemical responses [chlorophyll content， radial oxygen loss （ROL）， root-secreted TOC/DIC， etc.] were quantified. Tolerance was comprehensively evaluated using principal component analysis （PCA） coupled with a membership function method. The results indicated that high concentrations of SAs （5 000 μg·L^-1） significantly inhibited root development （P<0.05）， with root dry weight （inhibition rate of 75.7%， same below）， root number （76.1%）， maximum root length （60.9%）， and root porosity （52.2%） identified as sensitive indicators. Synergistic suppression of photosynthesis and ROL occurred： Chlorophyll content decreased by 6.3%-61.9% and ROL by 3.7%-86.4%， while root carbon release increased markedly （TOC by 12.19-fold， DIC by 2.03-fold） （P<0.05）. PCA combined with the membership function method identified root number， root dry weight， chlorophyll content， and TOC secretion as key tolerance indicators. Cyperus papyrus （D=0.781） and Alisma plantago-aquatica （D=0.650） demonstrated optimal comprehensive tolerance. Cyperus papyrus emerged as a critical stress-tolerant species for SA-polluted wetland remediation， maintaining photosynthetic homeostasis （chlorophyll increase up to 21.4% at high concentrations）， high ROL capacity （RI>0.97）， and carbon metabolic plasticity （12.19-fold TOC elevation）.