Mechanism of dehiscence in Geastraceae and Astraeus

Abstract

The opening of the fruiting body of the Geaster is caused by the dilation of the pseudo-parenchymal layer, of which only the cellular content is active. As the stellate lobes bend back, the mechanical layer is active, while the pseudoparenchymal layer, directly or indirectly, functions as a resistance layer. The backward curving of the stellate lobes is due to a process of dehydration contraction. With increasing water, a marked dilation of the hyphal walls is noted.

The hygroscopic movements of the lobes in Astraeus are caused by the dilatation capacity of the hyphal walls, in which the palisade layer and the white layer, both composed of thick-walled elements, function as a dilating layer, while the mechanical layer acts as a resistance fabric. Apart from the thickness of the walls, the direction of the hyphae is also important: each of the three layers is built by hyphae parallel to each other, but the direction of them in each of the layers is different: in the mechanical layer they are arranged in Meridional form, in the palisade with radial disposition, and in the white layer they bend in a curved way from the south to the radial direction.