Responses of Hebeloma radicosum fruit-bodies to light and gravity: negatively gravitropic and nonphototropic growth

Responses of the long-rooting agaric Hebeloma radicosum fruit-bodies to light and gravity were studied. In light from below or obliquely below, fruit-bodies grew straight downward with gills tilted and cap swollen and waved if they had emerged downward from the culture medium, or bent upward from the beginning if they had emerged obliquely downward. In light from above or obliquely above, they grew upward if they had emerged upward. Thus, they did not grow toward unilateral light from obliquely below or obliquely above, and hence their growth was nonphototropic and negatively gravitropic from the beginning of development. Even the straight downward growth seems to be latently negative-gravitropic. In the dark, fruit-bodies grew upward, forming pseudorhizas, but they remained immature; they matured only in the light. These characteristics may be related to the growth habits of the fungus colonizing deep in the ground, forming primordia there, and developing mature fruit-bodies on the ground. Received: March 26, 2001 / Accepted: July 12, 2001