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.
Effects of pesticidal treatments on the chlorophyll content of plant parts
The chemical control of pests and weeds as a mode of crop protection involves the poisoning of one organism without injuring the other too much. This is pursued by developing chemicals with a selective way of action, based upon biochemical or morphological differences between host and parasite or between cultivated plant and weed, and by using these pesticides within often narrow limits of concentration and formulation, and with consideration of such factors as the developmental stage of the crop and the weather conditions. Nevertheless, in many cases the margin between a sufficient pesticidal activity and phytotoxicity is rather small, particularly with herbicides, and the treatment frequently influences the crop beyond its pesticidal action by changing the growth rate or by causing discoloration. Moreover, non-toxic effects of the pesticidal treatment may also occur, usually showing up as differences in growth of developmental rates or in colour intensity of the crop.
The metabolism and translocation of 3-aminotriazole in plants.
Abstract 3-Aminotriazole was transformed to two new products (X and Y) in leaves. Compound X was the major product. Both products were characterized by the same ring system and free amino group as the parent aminotriazole. The formation of Compound X was a function of time. The formation of both compounds required healthy, turgid leaf tissue. Compound X, while having some toxicity, was not as toxic as the parent aminotriazole. Compound Y did not appear to be toxic. Aminotriazole-C 14 was rapidly transformed and translocated from leaves. After 5 days, roughly one-half of the radioactivity had migrated elsewhere. Of the total radioactivity, only 7% was in the form of aminotriazole.