Zur Feinstruktur der endophytischen Cyanophyceen von Gunnera chilensis Lam.

Abstract

Nostoc punctiforme lives within the cells of Gunnera chilensis . The blue-green algae are contained in the cytoplasm of the host cells and are surrounded by the plasmalemma of the higher plant. The cyanophyceae are surrounded by a 0.1—l μ m layer of mucilage without structure in the electron microscope and a 4-layered cell wall. Inside the blue-green algae are to be seen the typical thylakoids, derived from the plasmalemma, osmiophilic globules and nucleus equivalents. Nostoc punctiforme isolated from Gunnera chilensis and growing in artificial medium has the same cell wall as the symbiontic living algae. Other structural changes were not observed in the electron microscopic level. The number of Nostoc punctiforme in a cell are increased with the age of the colony. In old colonies the cytoplasm of the host cell are reduced to a very small border. Beside the normal Nostoc celles are obvious ly dead cells, which are very black, without structures and of half-moon shape. The dead cells in cultures of isolated Nostoc punctiforme have their shape but the cytoplasm gives no reaction with OSO 4 and only the thin lined thylakoids are visible. In sterile growing Gunnera plants the infection with Nostoc punctiforme was studied. The blue-green algae penetrate the intercellulares and later the cell wall. A scheme of this process is given and discussed according to the endosymbiont-hypothesis.