Differential Response of Selected Clones of Bindweed to 2,4-D

Abstract

Selected clones of field bindwecdl (Convolviilus arvensis L.) differing in susceptibility to foliage applications of 2,4-dichlorophenoxyacetic acid (2,4-D) were used in testing some of the various mechanisms proposed for the selective action of this chemical. TIhe differences found in external morphology, such as degree of puibescence and number of stomata, showed no relationship to the selective action of 2,4-D. Entry of the chemical inito the plant anid tranislocation within the stem also were not critical factors. The most pronounced physiological differences between resistant and susceptible clones of bindweed occurred at the cellular level. When incubated in a nutrient agar containing 2,4-D, excised stem sections of both clones produced callus tissue, but the callus of the susceptible clone, as compared to the resistant, was approximately double in volume, dry weight, and degree of hydration. With increasing age, stem sections of the susceptible clone became even more responsive to 2,4-D; the reverse was true for the resistant. The differential response of the two clones was less pronounced when 2,4-D was applied to the roots than when it was applied to the foliage.