Sporangiogenesis in Three Genera of the Saprolegniaceae. I. Pre-Sporangium Hyphae to Early Primary Spore Initial Stage

Abstract

The changes in cytoplasmic organization up to the early stages of primary spore initial delimitation are described in sporangia of four species of Saprolegniaceae. Organelle associations characteristic of asexual and vegetative stages are present in the cytoplasm of presporangium hyphae of Achlya debaryana. Organelles are aligned parallel to the axis of hyphal growth and the apex assumes the characteristic profile of a sporangium. Dense-body vesicles possibly originate from expanded cisternae of endoplasmic reticulum at this stage. In Dictyuchus anomalus, D. pseudodictyon, and Brevilegnia minutandra, nuclei of the primary spore initial stage orient radially in the cytoplasm with nucleus-associated organelles close to the sporangium wall. Nuclei in the central region of sporangia degenerate.