THE ROLE OF HYDROPHOBICITY IN ATTACHMENT OF UREDINIOSPORES AND SPORELINGS OF UROMYCES-VICIAE-FABAE

Aggregation of urediniospores of Uromyces viciae-fabae was caused by t heir hydrophobic surfaces. Solvent extraction of the lipids from the s urface of spores decreased aggregation and increased attachment of imb ibed spores to hydrophilic substrata. After landing on a substratum, u rediniospores oriented randomly and made contact with the surface via spines. Spine/substratum attachment was stable on hydrophilic and hydr ophobic substrata even when the alignment of spore aggregates was gros sly asymmetrical to the point of attachment. When incubated at 100% r. h. capillary condensation formed between the spore wall and contiguous surfaces and spores imbibed. After imbibition hydrophobic regions rem ained on the surface of spores. Extracellular matrix released from the germ pore and extending germ-tube contained a region of hydrophobicit y at its periphery. There was a positive correlation between protein c oncentration in the extracellular matrix and its ability to spread on a wax surface. Hydrophobic interactions contribute to the passive and active attachment of spores and sporelings.