PHOSPHORUS TRANSFORMATIONS DURING THE DEVELOPMENT OF THE OAT EMBRYO

THE DEMONSTRATION in recent years of the fundamental importance of "energy-rich" phosphorus compounds in the metabolism of animal tissues and yeast (Lipmann, 1941; Kalckar, 1942) raises the question of whether similar "energy-rich" compounds occur in plants, and whether they have an essential role in growth and other vital activity. In animal tissues and yeast the key "energy-rich" compound is apparently adenosine triphosphate which stores up the energy released on sugar breakdown and makes this energy available where necessary. This compound, furthermore, where it has been shown to occur, depends for its synthesis on the operation of some kind of fermentation mechanism like the Meyerhof-Emden system, as well as on some types of respiration. The demonstration by LePage and Umbreit (1943) of the phosphorylated intermediates which comprise such a system in Thiobacillus thiooxidans (an autotrophic bacterium which can satisfy all its carbon needs from CO2), together with the presence of adenosine triphosphate suggests that a fundamental phosphorylating system together with "energy-rich" compounds of the adenosine triphosphate variety may be of universal biological significance. Indeed there is some evidence in the literature which indicates that many of the phosphorylated intermediates found in muscle and yeast also occur in some plants and that phosphorylations actually take place (see Tanko, 1936, for an account of such experiments; also Kurssanov, 1941). The oat embryo is of particular interest in this connection, since the oat coleoptile has been the test object for growth experiments involving the auxins, and also because Albaum and Eichel (1943) have shown that there is a change in the character of the metabolism in the early growth stages (prior to 72 hours) as compared to the later stages (beyond 72 hours), fat presumably being the metabolite during early growth and sugar during later growth. Studies were, therefore, undertaken in an attempt to fractionate and identify the phosphorus compounds of the oat embryo, to ascertain whether the character of such compounds changes as the metabolism of the embryo changes, and finally to determinie whether "energy-rich" phosphorus compounds of the adenosine triphosphate variety are present, and how these vary during development. These studies are not yet complete, especially those involving the 1 Received for publication April 1, 1943. This work was done in the Laboratories of the Departnment of Agricultural Bacteriology, University of Wisconsin. The first author wishes to thank Mr. G. A. LePage and Mr. R. Emerson for many helpful suggestions. 2 National Research Fellow in the Natural Sciences 1942-43. identification of all the phosphorus compounds which occur. Nevertheless definite changes in the phosphorus fractions have been found, as well as evidence for high energy phosphorus compounds. These results are presented in the sections which f ollow. MATERIALS AND METHODS.-The essential method in the fractionations is that of LePage and Umbreit (1943). This method, in brief, consists of an intermittent trichloracetic acid extraction of homogenized oat embryos until no more phosphorus is removed and a separation of the combined extracts into several well defined fractions. Each fraction is then analyzed for individual compounds known to occur