Influence of Transpiration Stream on Plant Uptake and Translocation of Pharmaceuticals.

Plant could accumulate pharmaceuticals through the practice of land application of animal manure and biosolids from wastewater treatment plants and irrigation with reclaimed water. Plant transpiration flow could influence the extent of uptake and translocation of pharmaceuticals within plants. In this study, the uptake of pharmaceuticals by well-developed lettuce was studied in hydroponic systems with plant hormone abscisic acid (ABA) used to alter the amount of transpired water. The results revealed that ABA added in nutrient solution could effectively reduce the amount of water transpired through the lettuce. A good positive linear relation was observed between pharmaceutical mass accumulated in shoots and transpired water for caffeine (R² > 0.5) and carbamazepine (R² > 0.9). Both pharmaceuticals manifested a low affinity to lettuce roots. For trimethoprim a positive relation was observed for the accumulation in shoots (R² > 0.8) and roots (R² > 0.5) vs. transpired water. In contrast, no apparent relation between transpired water and accumulation in shoots was observed for lamotrigine, menesin, oxytetracycline, and tylosin. Overall, these results suggest that the uptake and distribution of pharmaceuticals in vegetables could be affected by the transpiration stream as well as the affinity of pharmaceuticals with plant tissues.