Ureide accumulation and drought inhibition of N₂fixation

Legume nitrogen fixation is inhibited by soil water deficit and under drought conditions ureidic legumes, such as common bean and soybean, accumulate ureides, which are the main products of N₂ fixation in these plants. Coleto et al. study genotypes of common bean, Phaseolus vulgaris, with variable degrees of N₂-fixation tolerance to water stress, and find variable accumulation of ureides in their leaves. There is no accumulation of ureides in the nodules of any of the genotypes and the rise in leaves occurs even after complete inhibition of N₂-fixation, probably as the result of remobilization of nitrogen from stressed tissues. They therefore conclude that shoot ureide accumulation after prolonged exposure to drought is not a cause of feedback inhibition of nitrogen fixation.