Riboflavin Nullification of Inhibitory Actions of 3-Amino-1,2,4-Triazole on Seedling Growth

Abstract

Chemical inactivation of the herbicide, 3-amino-l,2,4-triazole [amitrole] in illuminated solutions containing riboflavin or isoriboflavin was demonstrated by chemical analysis for amitrole and bioassay of exposed solutions for amitrole toxicity to growth of germinating seedlings. Under dark conditions, chemical inactivation of amitrole by flavins did not occur. Riboflavin, but not isoriboflavin, was effective in the partial reduction of amitrole inhibition of growth in the absence of light. Riboflavin dark-nullification of amitrole toxicity was observed with seedlings of alfalfa, barley, corn, cucumber, flax, oats, soybean, and wheat; but riboflavin had little effect on amitrole toxicity to seedlings of buckwheat, a species sensitive only to relatively high rates of the herbicide. All 9 species were approximately equally insensitive to amitrole in the presence of exogenous riboflavin. These results support the belief that a physiological mechanism is involved in the nullification of amitrole phyto-toxicity by riboflavin.