Germination and development of attachment structures by conidia of aquatic Hyphomycetes: light microscope studies

The time scales of conidial germination and production of postgermination attachment structures in species of the aquatic Hyphomycetes were investigated. The conidia of most species germinated within 2 h and formed appressoria within 6 h of settlement. Subsequent to settlement, appressoria were formed by all of the tetraradiate and branched conidia at the poles of the conidial arms. It is suggested that appressorium formation is an adaptation to aid fungal attachment to a substratum. Conidial germination was not influenced by the substratum; however, appressoria were both more numerous and more complex on a glass substratum. Mucilage was present on conidia, and mucilaginous sheaths were frequently observed to be associated with germ tubes and appressoria. The majority of species produced mucilages composed primarily of polysaccharide(s) with neutral or carboxyl functional groups.