Root Uptake and Xylem Translocation of Pesticides from Different Chemical Classes     

Fernando Sicbaldi  Gian Attilio Sacchi  Marco Trevisan  Attilio A. M. Del Re 《Pest management science》1997,50(2):111-119

A pressure-chamber technique was used to study the root uptake and xylem translocation of some fungicides, herbicides and an insecticide from different chemical classes in detopped soybean roots. Physiological parameters such as K⁺ leakage from roots, K⁺ concentrations in the xylem sap, and protein and ATP levels in the root cells were measured so as to evaluate any potential damage of this technique to the root system. HPLC was used to quantify the compounds in the xylem sap. The pressure-chamber technique has proved useful to study the root uptake and translocation of pesticides, does not damage the root system, and allows one to obtain appreciable volumes of xylem sap that can be analysed directly by HPLC, thus avoiding dependence on the availability of radio-labelled compounds. The concentration of each pesticide in the xylem sap showed a steady-state kinetic profile. Non-linear regression analysis was used to calculate the steady-state concentration and the time required to achieve 50% of the steady-state concentration (TSSC₅₀). TSSC₅₀ was well correlated with log K_ow; the more lipophilic the compound the more time was required to reach the steady-state concentration. The efficiency of translocation was assessed by the transpiration stream concentration factor (TSCF) and a non-linear relationship between TSCF and log K_ow was observed. The highest TSCF values were measured for those compounds with log K_ow values around 3, a lipophilicity value similar to that reported earlier in an analogous experiment with detopped soybean plants but slightly higher than that reported in earlier experiments with intact barley plants. Lower TSCF values were obtained with chemicals with log K_ow values below as well as above 3. © 1997 SCI.  相似文献