Distribution of carbofuran and dimethoate in flowers and their secretion in nectar as related to nectary vascular supply

摘要

The distribution of two systemic insecticides (carbofuran, dimethoate) in floral parts and nectar ofAjuga reptansL. (Lamiaceae),Brassica napusL. (Brassicaceae), andVicia fabaL. (Leguminosae), which differ in their types of nectary vascular supply, was determined. Radioactivity was detected in all floral organs when excised flowering plant tops were cultured in sucrose solution containing a combination of14C-labelled and formulated (unlabelled) insecticide. InA.reptansandB.napus, combined nectary tissue and nectar contained the most radioactivity on a fresh weight basis. Radioactivity was detected in floral nectar of all species, and in extrafloral nectar ofV.faba. Estimated concentrations of insecticide were much higher in extrafloral than in floral nectar ofV.faba; the presence of xylem in the nectary vasculature to the former may be responsible. However, the presence of xylem is not necessary for the secretion of systemic insecticides by nectaries.