Infection Structures and their Surface Changes during Differentiation in Uromyces fabae

Germ tubes of Uromyces fabae differentiated into appressoria which were deliminated either by one or two septa. These appressoria developed rapidlyon artificial membranes as well as on leaf surfaces. Fluorescein-conjugated wheat germ aggJutinin (WGA) bound strongly tO the germ tube walls of U. fabae and its binding ability did not differ significantly in 3, 5 and 7 hold germ tubes. The binding of WGA was less on the appressorium. Measurement of fluorescence with a lnicroscope photometer revealed two times more binding sites on germ tube walls than on appressoria. No binding of WGA was noticed on substomatal vesicles and infection hyphae. The binding of WGA was completely inhibited by preincubation with hydrolysate of chitin. Biflding patterns of other Jectins were quite different. Canavalia ensiformis lectin did not bind tO any structure, the Jectins of Griffonia simplicifolia and Lotus tetragonolobus bound weakly to all structures, the lectins of Phaseolus vulgaris and Arachis hypogaea bound only tO substomatal vesicles and infection hyphae, and the Ricinus communis lectin bound only tO the infection hyphae. Based on these observations it appears that infection structure surface of U. fabae, besides having chitin as a component, also contain some other carbohydrates such as galactOse and fucose.