Biochemical studies in the nitrogen metabolism of the apple fruit

Abstract

The effect of injecting, through a hole bored through the main stems, 2 vars. of apple trees with dilute solutions of NH4NO3, urea and asparagine was considerably to increase the total N content of the fruits as compared with fruit from uninjected trees. This increase was not, however, equally spread over all the fractions of N estimated (protein-, total soluble-, free ammonia-, asparagine- and amino acid N). The results for the peel and for the pulp of the fruits show the same general trend. In general while the absolute amount cf protein is slightly increased as a result of injection (all 3 solutions) the relative amt. is considerably decreased. The considerable increase in soluble N following injection is chiefly in the form of asparagine (glutamine is absent), amino acid N being little affected. In samples of "mature" fruit removed from the tree and stored at 9.5[degree] C for 54 days a net synthesis of protein was observed in the case of uninjected trees; there was no appreciable change in the ratio of protein to non-protein N in the fruit from the injected trees. The methods of sampling and of analysis used were the same as those described in a previous paper with the exception that an improved form of extractor (described, with figure) was used to obtain the soluble (in 85% alcohol) N.