Cytochemical Ultrastructure of Peltigera Canina: some Features Related to its symbiosis

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Abstract
Modified techniques allow the investigation of structures and inclusions in the lichen P. canina to following development from the growing edge of the thallus to fully differentiated areas towards the center. At .apprx. 60 .mu.m from the growing edge of the thallus, in area of cell division occurs. All the fungal material originates in this zone, whose cells have meristematic features. In the phycobiont, polyglucoside granules are specifically differentiated by Thiery''s test. Phycobilisomes are identified by a triple staining technique. Cyanophycin granules are stained with phosphotungstic acid at a low pH, corroborating the protein composition of these granules. Incubation in a lead nitrate medium allowed the ontogeny of the polyphosphate granules to be followed. In the mycobiont, the plasmalemma is strongly invaginated in hyphae close to blue-green algal cells and may initiate mesosome-like structures possibly involved in absorption of algal carbohydrates. Two types of vacuoles are demonstrated. The 1st one [diaminobenzidine (DAB) plus and Gomori minus], corresponds to common vacuoles which develop in cortical and medullar hyphae. The 2nd one (DAB minus and Gomori plus), is only present in the hyphae of the algal layer and corresponds to autophagic vacuoles. They are involved in the system mesosome-like structure/autophagic vacuole/primary lysosome, which could participate in the absorption of exogenous carbohydrates. The concentric bodies appear in great numbers in the zone of maximum cell division. As their number diminishes from this zone towards the differentiated parts of the thallus, they are passively distributed in all differentiated hyphae of the thallus. They consist of an electron-transparent core, from which a radiating system of unit membranes arises. Unit membranes are impregnated with a more or less electron-dense, granular substance which forms concentric layers surrounding the central core.

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