Uptake, translocation, and subcellular distribution of three triazole pesticides in rice

Triazole pesticides are widely used for the control of pathogenic fungi in crops, which were frequently detected in edible parts. Its extensive use has caused many environmental pollution and food safety problems. In this study, the uptake, translocation, and subcellular distribution of three triazole pesticides (triadimefon, tebuconazole, and epoxiconazole) in rice were investigated. The results showed that the three triazole pesticides could be taken up by rice roots, but their distribution in plant tissues were different. The accumulation of the three pesticides in rice root followed the order of epoxiconazole (4.26 mg/kg, 24 h) > tebuconazole (2.63 mg/kg, 24 h) > triadimefon (1.37 mg/kg, 24 h), while a reversed order was observed in rice shoots, triadimefon (0.48 mg/kg, 24 h) > tebuconazole (0.40 mg/kg, 24 h) > epoxiconazole (0.21 mg/kg, 24 h). The translocation of triazole pesticides within rice tissues involved both symplast and apoplast pathways, with triadimefon preferentially through by the apoplast pathway and epoxiconazole through by the symplast pathway. The proportions of triadimefon, tebuconazole, and epoxiconazole in the symplast and apoplast of rice plants were 15-33%, 6-31%, 7-37%, and 67-85%, 69-94%, 63-93%, respectively. The subcellular distribution revealed that all pesticides have a higher proportion in cell walls than in cell organelles and soluble components. Epoxiconazole has the highest accumulated capacity in the cell wall (45-67%) and triadimefon was more concentrated in the soluble components (24-29%). However, there were no significant differences in the amount of three pesticides in cell organelles. The distribution of the three pesticides in aboveground and underground parts of rice plant, uptake and transportation in symplast and apoplast pathways, and distribution in the subcellular tissue are all related to their hydrophobicity.