Uptake, translocation and accumulation of imidacloprid in six leafy vegetables at three growth stages

The uptake, translocation and accumulation behaviours of imidacloprid in six leafy vegetables, including Xiadi cabbage (XDC), Huaguan cabbage (HGC), Gaogengbai (GGB), Shanghaiqing (SHQ), Kangresijiqing (KRQ) and Ziyoucai (ZYC), were investigated under hydroponic conditions. Seedling stage (S-stage), rapid growth stage (R-stage) and maturation stage (M-stage) for each vegetable were considered. The root concentration factor (RCF), translocation factor (TF) and bioconcentration factor (BCF) were used to compare the difference. The results show that during 48 h of exposure, the total amount of imidacloprid taken up by the test vegetables increased with vegetable growth; however, the imidacloprid concentration in vegetable tissues varied significantly according to the variety and growth stage. For individual vegetables, imidacloprid was most easily accumulated into HGC and GGB shoots at R-stage, but into XDC, KRC and ZYC shoots at S-stage. For varieties, the ability of accumulating imidacloprid from solution to shoots seemed to follow the order of GGB > XDC > SHQ > KRQ > HGC > ZYC. Pearson's correlation analysis revealed significant negative correlations between daily transpiration and logBCF and between logRCF and logTF, indicating that the difference of uptake, translocation and accumulation behaviours of imidacloprid in vegetable varieties and growth stages may be related to the daily transpiration and the ability of concentrating imidacloprid in vegetable roots.