Les cystides à cristaux des Inocybes (Agaricales): étude histochimique et cristallographique

Abstract

Histochemical and cristallographic studies were performed in light microscopy and scanning electron microscopy on crystal-bearing cystidia of several Inocybe spp. (Agaricales) and confirmed the excretory function of these sterile cells of the hymenium. At the apex of these bottle-like cells, the wall had an axial polysaccharidic matrix rich in carboxyl groups. It also presented an enhanced permeability and a local concentration of Ca2+. Functioning as an hydathode, the cystidium secreted, at its apex, an aqueous droplet into which twin crystals developed. In addition, crystal sand were found in the cystidium wall. These two crystalline products were calcium oxalate as confirmed with anthracene green and the Pizzolato test. A detailed crystallographic study showed that these twin crystals undoubtedly belong to the monoclinic system, i.e., the monohydrated form of the calcium oxalate or whewellite. In the case of Inocybe asterospora Quél., these grouped crystals were formed regularly by two pairs of twin crystals. The identification and localization of the Ca2+ ions have been determined with the scanning electron microscope by means of the X-emission pictures and the resulting energy dispersive X-spectrum for the latter element. Key words: Inocybe, cystidium, hydathode, calcium oxalate, whewellite.