Interactions between a fungal endophyte and gametophyte cells in <i>Psilotum nudum</i>

Abstract

Mature Psilotum gametophytes found in greenhouse pots containing plants of Hoya, Philodendron, Aspidistra, or Diffenbachia were processed for microscopy. An endophytic fungus was abundant in the rhizoids and in most cortical parenchyma cells except at the growing apices. Although the fungus has not been identified, it is an aseptate fungus with coarse hyphae which occasionally form vesicles. Endophytic fungal hyphae store quantities of lipid which appear to be released into the host cytoplasm upon fungal degeneration. This lipid and the remnants of hyphal cell walls may be used as an energy source by the achlorophyllous gametophyte. Gametophyte cell organelles, including the nucleus, appear to degenerate after fungal breakdown, and the cells presumably die. Although reinfection of cells containing degenerated hyphae was found, it was not particularly common.