The Ultrastructure of the Symbionts of Rhizocarpon Geographicum, Parmelia Conspersa and Umbilicaria Pustulata Growing under Dryness Conditions.

Abstract

The dryness-induced ultrastructural changes of both myco- and phycobiont of three lidien species (R. geographicum, P. conspersa, and U. pustulata) have been studied over three months and half, period of time. During this time other ecological factors, such as rock substratum, temperature, light and gas interchange were unaltered compared to the natural conditions. A large number of ultrastructural changes were observed in the mycobiont as well as in the phycobiont (Trebouxia) and often, cells showed a highly disorganized morphology. The most importan! ultrastructural modifications were: 1. pyrenoglobuli of the algae were peripheral, 2. new and unknown structures were observed ¡n the phycobionts of both R. geographicum and U. pustulata as well as in the mycobiont of the latter species.