Light And Electron Microscopic Study Of The Lichen Xanthoria Parietina Infecting Fruit Trees In Egypt

Ali M. Koriem
Efficient Productivity Institute, Zagazig University, Egypt.

Abstract

The lichen Xanthoria parietina is the most abundant lichen infecting fruit trees in Egypt. The anatomy of the lichen thallus showed a typical foliose lichen layers i.e. upper cortex, algal layer, medulla, lower cortex and rhizines. The rhizines were spreading over the cork tissues forming foot-like structure. No penetration was noticed except the loosely cork layer in the center point of contact. The fine structure including cellular and subcellular structures as well as the interaction between the symbionts were investigated by electronmicroscopy. Two layered cell wall, concentric bodies, one pore septum and intrahyphal-hypha were observed in the mycobiont hyphae. The ultrastructure of the phycobiont showed that Trebouxia cells had pyrenoids that contain electron dense globules (pyrenoglobuli). The interaction between the symbionts ranged between wall to wall contact to intramembranous haustorium. Intracellular haustoria were absent.