THE EFFECT OF 3-AMINO-1,2,4-TRIAZOLE ON THE UPTAKE, RETENTION, DISTRIBUTION, AND UTILIZATION OF LABELLED PHOSPHORUS BY YOUNG BARLEY PLANTS

Abstract

Seedlings of barley were grown to the 3-leaf stage in phosphate-free nutrient solution and AT was added at such times that the roots were in contact with 100 p.p.m. of the compound for 96, 48, 24, 4, 1, or 0 hours immediately prior to transfer to labelled phosphate solution for 1 hour. The plants were then returned to phosphate-free nutrient solution and harvested 1, 2, 4, 24, 48, and 96 hours after the start of the contact with radioactive solution. In an experiment designed to determine the effect on utilization of phosphate the immersion in AT was of 48 hours' duration.Exposure to AT diminished uptake of P³² but also decreased the subsequent loss to the environment. The activity in both acid-soluble and acid-insoluble fractions of the root was reduced by treatment but exposure to AT for up to 48 hours increased the amount of P³² translocated to the shoot. The proportion of the absorbed phosphate found in the shoots of treated plants was higher than in the controls.For 2 to 4 hours the incorporation of P³² into both acid-insoluble (nucleic acids, phospholipids, phosphoprotein) and acid-soluble (nucleotides, sugar phosphates, inorganic phosphate) fractions showed little deviation from normal, but by the end of 24 hours AT treatment caused a decrease in the acid-insoluble fraction of both roots and shoots. The pattern of esterification was changed but little.Apparently the effect of AT on phosphate metabolism is not concerned with the reactions of oxidative phosphorylation or of glycolysis, but is confined to the processes involved in the incorporation of phosphate during the synthesis of nucleic acids.