The metabolism of [14C]aldicarb in the root of sugar beet plants

Abstract

AbstractSugar beet plants were grown in the field, after in‐furrow application of [14C]‐ aldicarb (3 kg of aldicarb ha−1) at planting. The ripe sugar beet plants were harvested, and the roots were analysed. The roots were fractionated according to a procedure similar to the normal beet‐sugar manufacturing process. Expressed as a proportion of the total radioactivity incorporated into the root, the pulp contained 29.7%, the lime cake 9.7%, the crystallised sugar 17.7% (which gave, with the radioactivity found in the sugar in the molasses, a total of 20.7% of the radioactivity in the total sugar), and the molasses, 42.9%. A part of the labelled carbon from the radio‐ active aldicarb and its metabolites had thus been metabolised and incorporated into sugar molecules. Except for the radioactivity in the sugar and in the lime cake from the processing, the proportion of radioactive non‐conjugated organosoluble compounds was very low (2.6%), and perhaps partially corresponded to the very low amount of aldoxycarb (aldicarb sulphone) in the root (less than 0.001 mg of [14C]‐aldicarb equivalents kg−1 fresh weight). Hydrolysis of the molasses yielded free radioactive 2‐methyl‐2‐(methylsulphinyl)propan‐1‐ol (3.1%), 2‐mesyl‐2‐methyl‐propan‐I‐ol (8.9%) and 2‐mesyl‐2‐methylpropionic acid (12.0%) which had been conjugated to plant constituents in the root. The corresponding concentrations (expressed as mg of [14C]aldicarb equivalents kg−1 fresh weight of root) were 0.004, 0.011, and 0.016, respectively. No aldicarb, aldicarb sulphoxide or aldoxycarb (nor the corresponding nitrile, generated from aldicarb during the fractionation procedure) was liberated by the hydrolysis, indicating the absence of conjugates of these compounds in the root.