Riboflavin Nullification of Inhibitory Actions of 3-Amino-1,2,4-Triazole on Seedling Growth.
The physiological mechanislmis involved in the toxic actions of 3-amino-1,2,4-triazole (amitrole) have been actively investigated since the chemical was first introduced as a potential herbicide in 1954 (2). Much of the research has been guided by hypotheses involving one of three major metabolic processes: A, porphyrin synthesis, B, cation functions, and more recently C, the metabolism of purines and their derivatives. The extensive literature associated with the first two categories will not be considered herein. Amitrole interferences in some of the biochemiiical processes of the third category now appear to be the actions of nmajor physiological importance in the response of plants to the herbicide. Much of the pertinent research deals with attempts to find physiological compounds capable of reducing the toxicity of amitrole to various organisms. The most effective conmpounds are purines (23, 24) or histidine (13, 23) for unicellular plants anid riboflavin or riboflavin derivatives (22, 24) for higher plants. The investigations reported herein Nwere initiated as a result of my observations that the riboflavin effect could not be denmonstrated with barley seedlings by tecliiques that had been used successfully with other herbicidemetabolite combinations (9, 14, 18). The objectives of this study were: A, to develop techniques by whiclh the riboflavin nullification of amitrole toxicity could be observed with higher plants, and to compare adenine and histidine with riboflavin by these techniques; BR, to consider the possibilitv that the riboflavin effect was the result of non-physiological processes: C, to compare the effectiveness of riboflavin in species of higher plants that differ in their response to amitrole, and D, to determine if certain other metabolites of theoretical interest might give additional reductionis in amitrole toxicity.
Effect of histidine on the inhibitory action of 3amino-1,2,4-triazole.
HE present experiments were part of a study to determine the ITmechanisms by which herbicides affect plant growth and to find metabolites which protect growth against the inhibitory actions of herbicides. Bakers' yeast was selected for use in preliminary investigations because its rapid growth rate facilitates examination of large numbers of herbicide-metabolite combinations. The experiments reported herein present evidence which implicates histidine metabolism as a growth process which is sensitive to 3-amino-1,2,4triazole [amitrole].2
The effect of 3-amino-1,2,4-triazole on phosphorylase of Oscillatoria princeps.
Abstract 1. 1. The inhibitory effect of 3-AT on Oscillatoria princeps phosphorylase is probably due to the chelation by 3-AT of the essential metal required by this enzyme. 2. 2. The inhibition of this phosphorylase by 3-AT can be effectively reversed by the addition of manganous or ferric ions only in the proper concentrations for forming the bivalent and trivalent chelates. 3. 3. Evidence is presented for the 3:1 structure of the ferric chelate of 3-AT.