*3.1. Effects of Antibiotic Exposure on Pakchoi Growth*

The effects of antibiotics on pakchoi growth were assessed by analyzing the growth parameters. The detected values of plant height, root length, and fresh biomass are shown in Table S4. Figure 1 shows the changes of pakchoi growth at different antibiotic types and doses. Compared with the control, the growth indices increased when exposed to 50% MIC levels of antibiotics (*p* < 0.0001 for the plant heights and *p* < 0.001 for the fresh biomass values). When the exposure dose was increased to MIC levels, this growth-promoting effect was maintained in CPL-treated plants. However, the TC- and SMX-treated plants were significantly inhibited (*p* < 0.01), as indicated by the growth parameters being less than those of the controls. According to the detection of growth inhibition rates (data shown in Table S4), fresh plant biomass was the most affected parameter (fresh biomass > root length > plant height) under antibiotic exposure. SMX showed the greatest impact on pakchoi growth in the three antibiotic types and CPL had the least inhibition on the plants.

**Figure 1.** Effects of different dosages and types of antibiotic exposure on the growth of pakchoi under hydroponic condition. (**A**) Plant height; (**B**) Root length; (**C**) Fresh biomass. Values are mean ± SD (*n* = 10). Different letters on the top of the error bars indicate statistically difference among the treatments (*p* < 0.05). TC, tetracycline; CPL, cephalexin; SMX, sulfamethoxazole; MIC, minimum inhibitory concentration; SD, standard deviation.
