The Response of Aspen Roots to 3-Amino-l,2,4-triazole.

A technique for following the root elongation of rooted cuttings of Populus tremula on moist filter paper is described. Aminotriazole caused inhibition of root elongation, when applied to the mature leaves in quantities of 0.1 mg. per plant or more or to the growth solution in concentrations from 3x10^-5 M. In both cases the response was delayed about 24 hours. Only high concentrations applied to the roots caused a considerably more rapid response. The onset of the inhibition was usually accompanied by the appearance of necroses in the extending part of the root, while the meristem and the mature parts of the root showed no visible injuries. In spite of this injury the root tip, at moderate concentrations of ATA, continued to elongate at a slow rate. The inhibition of root growth appeared before chlorosis or other injuries to the leaves become visible. The roots of wheat seedlings grown in the dark showed a similar sensitivity to the inhibitory effect of ATA, while the roots of pea seedlings were less sensitive. [ABSTRACT FROM AUTHOR]