[Chlorella enhances the resistance of wheat to sulfamethoxazole]

To clarify mechanisms underlying the enhancing effect of applying Chlorella sorokiniana on the resis-tance of wheat (Triticum aestivum) seedling under sulfamethoxazole (SMX) stress, we conducted experiments on C. sorokiniana cultivation and wheat seedling hydroponics. There were four treatments with the concentration of 0, 25, 50, 100 and 200 mg·L^-1 SMX in the culture medium of C. sorokiniana. After 7 days cultivation, algal growth, photosynthetic activity, and SMX removal capacity were analyzed. Subsequently, 0, 25, 50, 100 mg·L^-1 of SMX and C. sorokiniana culture solution (0.5 g·L^-1) were applied to the hydroponic solution of wheat seedlings for 15 days cultivation. We measured the growth, photosynthetic characteristics, and SMX content in both the see-dings and culture medium. The results showed that C. sorokiniana exhibited strong tolerance to SMX, maintaining effective growth under 200 mg·L^-1 SMX. After 7 days cultivation, the maximum net removal rate of SMX from the culture medium reached 64.1%, with degradation being the main removal pathway under lower SMX concentrations. SMX stress significantly inhibited the growth and photosynthetic activity of wheat seedlings, while the application of C. sorokiniana effectively alleviated this stress effect. Compared to the (25, 50, 100 mg·L^-1) SMX treatment group, the seeding height, root length, fresh weight, and dry weight were elevated by 3.7%-10.9%, 2.0%-11.1%, 9.3%-21.6%, and 6.7%-19.4%, respectively, and photosynthetic activity was also improved. The application of C. sorokiniana significantly increased the SMX removal rate in the hydroponic solution, while reducing SMX accumulation in wheat seedings and residual SMX in the hydroponic solution by 13.6%-39.6% and 8.9%-22.7%, respectively. In summary, C. sorokiniana reduced SMX levels in the rhizosphere environment and wheat seedings through absorption and degradation, thereby mitigating toxic effects of SMX on wheat growth. The findings could provide insights for the green prevention and control of antibiotic residue pollution and the safe production of wheat.