*3.2. Antibiotic Uptake by Pakchoi*

The edible portions of pakchoi samples, both controls and antibiotic-exposed plants, were separated and the concentrations of TC, CPL, and SMX within plants were determined to evaluate the uptake of antibiotics by plants, as shown in Figure 2. The results indicated a concentration range from 6.9 to 11.8 <sup>μ</sup>g·kg−<sup>1</sup> for TC (Figure 2A), 26.4 to 48.1 <sup>μ</sup>g·kg−<sup>1</sup> for CPL (Figure 2B), and 18.1 to 35.3 <sup>μ</sup>g·kg−<sup>1</sup> for SMX (Figure 2C) in plants, respectively. However, no antibiotic accumulation was detected in the controls. Obviously, the antibiotic concentrations in the vegetables increased as the antibiotic dose increased in the culture solution. The mean CPL concentration in the CPL-treated

samples was higher than those of the other antibiotic residuals in their corresponding treated samples when the exposure concentrations were at MIC levels.

**Figure 2.** Accumulation of antibiotics in hydroponic pakchoi under different dosages of antibiotic exposure. (**A**) TC exposure treatment; (**B**) CPL exposure treatment; (**C**) SMX exposure treatment. Values are mean ± SD (*n* = 3). Different letters on the top of the error bars indicate statistical difference among the treatments (*p* < 0.05).
