DESTRUCTION OF C-14-LABELED AND N-15-LABELED AMINO-ACIDS AND NUCLEIC BASES IN SOIL AND THE SUPPLY OF THEIR TRANSFORMATION PRODUCTS TO PLANTS

The destruction of amino acids (glycine and alanine) and nucleic bases (uracil) in soil was evaluated according to the mineralization losses of tracer C-14 occupying a certain position in the molecule. Carbon o f carboxyl groups of amino acids was lost most rapidly, carbon of the pyrimidine ring of uracil somewhat more slowly, and carbon of the meth ylene group of glycine even more slowly. Microorganisms play a major r ole in the decomposition of both amino acids and also nucleic bases. T he losses of nitrogen from different parts of the plow horizon which w ere detected experimentally are caused mainly by the descending migrat ion of nitrates, which form in the process of mineralization of amino acids and uracil labeled with N-15. In the first year after the experi ment was set up, the ratio of tracer carbon and nitrogen which entered the plants averaged about 1:300, which is indirect proof that the maj or portion of the tracer nitrogen which entered the plants was mineral ized beforehand in the soil.