THE NATURE OF THE INHIBITING SUBSTANCE EMITTED BY GERMINATING UREDIOSPORES OF PUCCINIA GRAMINIS VAR. TRITICI

Abstract

The self inhibition of germination of urediospores of Puccinia graminis Pers. var. tritici Erikss. & Henn. has been consistently demonstrated in Warburg flasks. Four ways of overcoming the effect of the inhibitory substance have been discovered: use of a sufficiently large volume of water in relation to weight of spores; the placing of a silver nitrate solution in the center well; and the introduction of acetone or ammonia vapor into the flask atmosphere. The vapor of trimethylethylene inhibits germination of the urediospores in the same way that the natural inhibitor does, and the same means can be used to counteract its effects. The similarity of the absorption spectra of the inhibitor and of trimethylethylene in acetone solutions indicates that trimethylethylene is the natural inhibitor. Cyclohexene has formative and inhibitory effects on the germ tubes and these effects can be overcome by vapor of acetone.