Transpiration Effect on the Uptake and Distribution of Bromacil, Nitrobenzene, and Phenol in Soybean Plants

Abstract

Abstract The influence of transpiration rate on the uptake and translocation of two industrial waste compounds, phenol and nitrobenzene, and one pesticide, 5‐bromo‐3‐ sec ‐butyl‐6‐methyluracil (bromacil), was examined. Carbon‐14 moieties of each compound were provided separately in hydroponic solution to mature soybean plants [ Glycine max (L.) Merr. dwarf cultivar Fiskeby v] maintained under three humidity conditions. The uptake of each compound was determined by monitoring the removal of 14 C from the hydroponic solution. The extent to which 14 C was adsorbed to roots and translocated to plant shoots and leaves was examined by assaying root and shoot parts for 14 C. Bromacil was taken up slower than the other chemicals, had the most 14 C translocated to the shoot, and the amount translocated to the shoot responded directly to the rate of transpiration. In contrast, both phenol and nitrobenzene were rapidly lost from solution and bound to the roots. Less than 1.5% of the 14 C from phenol or nitrobenzene was translocated to the plant shoots. Increased transpiration rates had little influence on root binding of 14 C; however, increasing transpiration rate from low to medium was associated with an increased uptake of nitrobenzene. The three chemicals studied have similar Log K ow values, but their interactions with soybean were not the same. Thus, despite the usefulness of the octanol/water partitioning coefficient in predicting the fate of organic chemicals in animals and in correlating with root binding and plant uptake for many pesticides, log K ow may not be equally useful in describing uptake and binding of nonpesticide chemicals in plants.