Translocation of Herbicides and Assimilates in Red Maple and White Ash

Abstract

Herbicidal dosages of 3-amino-1,2,4-triazole (amitrole) or 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) were applied to red-maple and white-ash trees. Amitrole applied to either leaves or stems was absorbed and transported throughout the trees. In contrast, 2,4,5-T was not exported from the leaves and did not appear to be symplastically translocated following application to stems. Leaves on similarly treated trees were exposed to 14CO2, and the effect of the herbicides on the movement of 14C-assimilates was noted. Both amitrole and 2,4,5-T caused significant transport of 14C-assimilates into the veins of fully expanded leaves from the 14CO2-treated leaf. Translocation of labeled assimilates to the roots was reduced if the 14CO2-treated leaves had been sprayed previously with either herbicide. When the 14CO2-treated leaf had not been sprayed, transport of labeled assimilates to the roots was only moderately affected by amitrole or 2,4,5-T applied to the remainder of the shoot.