The Degradation of 2,4-Dichlorophenoxyacetic Acid by Maize Cells in Suspension Culture

Abstract

Summary About 40 per cent of [1-14C]2,4-D was degraded by maize cells during the first 3–4 days of subculture. A comparison of the metabolism of [1-14C]2,4-D and [2-14C]2,4-D led to the conclusion that the first step in 2,4-D degradation is the splitting off of the side chain. The rate of degradation increased several times during the first 15 h of subculture and then declined concomitantly with a decrease of intracellular 2,4-D content. An estimation of the relative rate of degradation (rate of degradation: intracellular 2,4-D content) revealed it to be diminished when 2,4-D content in the cells decreased under the influence of some experimental factors. The presence of two pools of intracellular 2,4-D — one fast-effluxing and the other saturable slowly-effluxing is postulated on the ground of efflux analysis. It was concluded that only 2,4-D in the fast-effluxing pool is available for degradation. The influence exerted by some parameters (initial 2,4-D concentration, pH of the medium, suspension density, physiological state of the cells) on the rate of 2,4-D degradation depends on the changes of intracellular 2,4-D content, compartmentation of 2,4-D and metabolic activity.