アサクサノリの生化学的研究-II

Abstract

The purpose of the present work is to compare the rates and extents of utilization of such different nitrogen sources as ammonium chloride, sodium nitrate, sodium nitrite, urea and several amino acids by Porphyra tenera. The frond of this alga was cultured for a period of 2 days with one of these compounds as the sole nitrogen source. The comparison was made on the basis of both the decreasing rate of the added nitrogen in the culture media and the forms and amounts of the nitrogenous constituents of the frond. The results obtained are shown in Tables 1-4, and are summarized as follows: (1) Ammonia was easily absorbed by the frond, in which the soluble nitrogenous compounds, chiefly amide, alanine, glutamic acid and citrulline, were accumulated. The insoluble nitrogen in the frond, however, did not increase so markedly as the soluble nitrogen. (2) Nitrate was also absorbed easily, and usually a large amount of nitrate was accumulated in the frond. This suggests that further reduction and conversion of nitrate to organic forms might be restricted by the capacity of the alga to reduce it. However, since the use of nitrate as the nitrogen source characteristically leads to a relatively low content of soluble nitrogen, it seems that this nitrogen source is generally more conducive to the protein synthesis than ammonia or nitrite. (3) The permeability of the frond to nitrite was not so great. Once nitrite was absorbed, however, it was reduced entirely and caused a marked increase of soluble nitrogenous compounds in the frond, as in the case of ammonia. (4) The rate of absorption of urea was so variable in different experiments that we have not yet been able to formulate any characteristic feature of urea utilization in this alga. (5) Glycine, alanine, arginine and sodium glutamate were scarcely or not absorbed by this alga in the present experiments.