Effect of exogenous NH4+-N supply on distribution of ureide content in various tissues of alfalfa plants,Medicago sativa

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Abstract
The profile of ureide (allantoin and allantoic acid) accumulation in various tissues of alfalfa, Medicago sativa, was surveyed under different nitrogen nutrient conditions. In the xylem sap, the ratio of ureides to asparagine of two amide type legumes, alfalfa and Lotus corniculatus, was 14 times lower than that of a typical ureide type legume, soybean when they grew in a nitrogenfree nutrient solution. In alfalfa plants, the ureide concentration was higher in the lateral roots and in the nodules than in other tissues. In the main root the concentration of ureide increased gradually towards the root tip. This distribution of ureides, except for the nodule tissues, was similar to that of the non-nodulating soybean variety. Application of ammonium sulfate to the root system slightly increased the ureide content in various tissues of alfalfa in the short term, while the ureide content in the nodule tissues rather decreased after the treatment. The data indicated that ureide accumulation mainly occurred in roots and leaves in the case of alfalfa in the same way as in non-nodulating soybean plants, although the content was much lower than in soybean nodules.