Root uptake and translocation of ¹⁴C-sulfadiazine in leaf lettuce

The presence of antibiotics in agricultural soils raises concerns regarding their uptake by plants and subsequent entry into the food chain. Therefore, this study aimed to evaluate the root uptake and translocation of the antibiotic sulfadiazine (SDZ) radiolabeled with carbon-14 (¹⁴C) in leaf lettuce (Lactuca sativa var. crispa), a vegetable frequently consumed raw. The experiment consisted of applying ¹⁴C-SDZ (8.01 × 10³ Bq) per pot to the soil, with plants cultivated in individual pots and sampled at 1, 3, 6, 8, and 10 days after application (DAA). The distribution of ¹⁴C-SDZ in the plant was assessed by autoradiography, sample oxidation using a biological oxidizer, and quantification by liquid scintillation spectrometry. The results demonstrated progressive root uptake of ¹⁴C-SDZ, with the fraction recovered in roots increasing from 2.27% (1 DAA) to 5.98% (10 DAA). However, translocation to the aerial parts was minimal. While most of the applied ¹⁴C-SDZ remained in the soil (47.63-68.78%), only 0.69-1.23% was translocated to the stem and 0.36-0.41% to the leaves. These results indicate that ¹⁴C-SDZ is absorbed by lettuce roots, but its translocation to aboveground tissues is limited, resulting in predominant accumulation in the root system. This restricted distribution pattern of ¹⁴C-SDZ highlights the importance of understanding root uptake and translocation processes within the soil-plant system.