THE RELATION OF SELF-INHIBITION OF GERMINATION TO THE OXIDATIVE METABOLISM OF STEM RUST UREDOSPORES

Abstract

Studies were made on the oxidative metabolism of stem rust uredospores under self-inhibited conditions and when self-inhibition was removed. The oxidative metabolism of self-inhibited spores is characterized by the following features: the oxygen uptake declines rapidly; the respiration is mainly based on a fatty acid oxidation apparently bypassing the Krebs cycle (malonate insensitivity); and the enzymes of carbohydrate breakdown are more or less inactive. Compounds that are able to overcome self-inhibition stimulated oxygen consumption. Simultaneously an intensified utilization of endogenous fatty acids was initiated and also an increased malonate sensitivity. Longer incubation periods with stimulants resulted in germination and in a concomitant activation of carbohydrate metabolism. The catalytic effect of pelargonaldehyde or other stimulants in overcoming self-inhibition was reproduced by the administration in substrate concentrations of suitable respiratory material such as butyrate and propionate. The stimulated respiration induced by these substances appears to be a prerequisite for germination.The possible significance of the above findings from the point of view of host–parasite relations is discussed.