Behavior of the Inner Wall Layer of the GerminatingFuligo SepticaSpore: Evidence of Peroxidase Activity

Abstract

The spore wall of Fuligo septica is composed of an exterior electron-dense, spined layer and an interior more electron-transparent, fibrous layer. The fibrous material in the interior layer is often tightly packed. During germination, the exterior layer splits, but the inner layer does not. A remnant of this inner layer surrounds the newly released protoplast if the remnant is not left behind. The remnant appears to be derived from the fibrous wall material. However, swarm cells appear to be free of structural wall components. Cytochemical tests suggest peroxidase activity in the inner wall layer. Initial localization of peroxidase activity near the split in the outer wall may indicate peroxidase plays a role in the germination process. Light microscopic observations of Fuligo septica (L.) Wiggers show that during germination the spore wall ruptures to form a wedge-shaped split through which the protoplast emerges (11). Electron micrographs of this species indicate that the spore wall is composed of two layers: an outer electron-dense layer with spines and an inner, relatively electron-transparent layer (3). A two-layered wall has been observed in other Myxomycetes such as Arcyria cinerea (Bull.) Pers. (17) and Stemonitis virginiensis Rex (18). In these two species the inner layer is elastic and remains intact longer than the outer layer. However, in F. septica there are no published studies dealing with the behavior of the inner layer. In the present study, we examined the inner wall layer and compared its behavior with that of other Myxomycetes.