INVESTIGATIONS ON NITROGEN COMPOUNDS AND NITROGEN METABOLISM IN PLANTS. I. THE REACTION OF NITROGEN COMPOUNDS WITH NINHYDRIN ON PAPER: A QUANTITATIVE PROCEDURE

This is the first of a group of papers which will record investigations on nitrogen compounds and their metabolism in plants. The work was undertaken not only because of the intrinsic interest of nitrogen metabolism, but even more because it had become so apparent that other vital phenomena would only be fully comprehended when their relations to nitrogen metabolism were revealed (26, and refs. there cited; 27). Plant respiration?long considered in terms only of carbohydrate breakdown?has recently been shown to include a moiety which varies concomitantly with protein synthesis and the metabolism of amino acids. This was especially true of the cells of the potato tuber (24), under the conditions which promote accumulation of salts. In another series of papers (for references see 21), the ability to accumulate salts, now somewhat generally conceded to be a property of active cells and dependent upon their aerobic respiration, has also been associated in a variety of ways with cells able to grow and to synthesize protein and with factors able to foster this process (22, 23, 24). For the particular case of the potato tuber, it was recognized that aerobic respiration, protein synthesis from the stored reserves of soluble nitrogen and the accumulation of anions (Br) and cations (K) varied pari passu under the influence of a wide range of conditions. Observations such as these led to the view that the energy of respiration was made available simultaneously for both salt accumulation and the protein synthesis with which it appeared to be linked. The necessary point of contact between the energy derived from aerobic respiration with the metabolism of nitrogen compounds and salt accumulation, promised, therefore, to be fundamental to the understanding of all of these processes. Prior to the work now to be described, some progress had been made by analytical methods which could fractionate the soluble nitrogen of the cells only into the amino-N and amide-N fractions (22). The total amide-N was further separable into glutamine-amide-N and asparagine-amide-N (25), and it became apparent that these two substances stood in quite different relationships to protein synthesis (26, and refs. there cited). Further