Septal and lateral pores in the fungal endophytes of two pasture grasses

Abstract

Septal spores of two fungal endophytes of Lolium and Festuca are more elaborate, in presporulation hyphae, than the simple pore of many ascomycetous fungi. The pore of the Gliocladium-like endophyte consists of a dome-shaped, membraneous cap formed of vesicle-like structures that encloses the aperture. Woronin bodies in the pore vicinity appear to bear fine fibrillar processes extending radially from their surfaces, often making contact with the pore cap. In septal pores of the Phialophora-like endophyte the hemispherical boundary of the pore lumen bears an irregular electron-opaque deposit, and fibrillar processes from Woronin bodies have not been observed. Lateral pores occur in both endophytes in areas of massed contiguous hyphae. Reduction of two hyphal walls to a narrow strip occurs at the pore site. Development of a pore between the hyphae probably results from degradative activities of a fibrillar band extending between two Woronin bodies, one in each hypha, and penetrating the dividing wall. In lateral pore formation, involvement of Woronin bodies with an associated fibrillar band at the future pore site may support their enzymatic nature. Similarly, in septal pores of the Gliocladium-like endophyte, fibrillar extensions from Woronin bodies to the septal pore cap may indicate enzymatic control of the pluglike contents of the pore. Key words: fungi, septal pores, lateral pores, ultrastructure, endophytes, grasses.