Carbohydrate and Lipid Metabolism during Germination of Uredospores of Puccinia graminis tritici

Uredospores of Puccinia graminis (Pers.) tritici (Eriks. and Henn.) were uniformly labeled with 14C by permitting the host (Triticum aestivum L.) to carry out photosynthesis in ^{14}\text{C}{}_{2}$ during the process of spore production by the obligate parasite. The use of 14C labeled spores provided advantages in a study of the utilization of endogenous substrates at frequent intervals with small amounts of spores under conditions conducive to germination. Because of previous uncertainties about the nature of the substrates of importance to germination, a detailed study of carbohydrate and lipid components, both in the spores and in the germination medium, was made during the first 7 hours after placing the spores on aqueous media. Diethyl ether and 80% ethanol soluble metabolites each constituted approximately 20% of the total spore carbon. During the first hour nearly 60% of the 80% alcohol solubles disappeared from the spores while the total ether soluble material did not change appreciably. A significant part of the 80% ethanol soluble materials appeared in the germination medium. During germination and germ tube extension, there was rapid utilization of trehalose, arabitol and mannitol even though appreciable amounts of these materials were present as exogenous pools in the germination medium. Although the total amounts of ether soluble components did not change as drastically as the carbohydrate fraction, there was extensive utilization of palmitic, oleic, linolenic and 9,10-epoxyoctadecanoic acids. The results indicate that the germination process in spores of obligate parasites is not based solely on the utilization of lipids and some possible roles of the changes in internal and external pools of soluble carbohydrates are discussed.