16. Brown, Jr. R. M. and R. Wilson. 1968. Ultrastructure of the lichen Physcia aipolia (Ehrh) NYL. J. Phycol. 4:230-240.

16. Summary

The ultrastructure of the lichen Physcia aipolia was studied in the desiccated and hydrated states. No significant structural variation between these 2 states was noted for the fungus. The fungus contains unusual ellipsoidal structures heretofore unobserved. Their possible role in the formation of membrane is discussed. The plasmalemma of the fungus is convoluted while that of the alga is smooth. The convoluted projections have a "double-unit membrane" structure similar to fingerlike projections of the ellipsoidal bodies. With OsO4 fixation crystals are preserved, enclosed in unit membrane sacs which extend to the convoluted surface. The pyrenoid of the associated alga does not produce starch in the desiccated condition, and electron-dense granules are present in the matrix associated with chloroplast lamellae which enter this area. In the hydrated condition, the alga contains abundant starch in the pyrenoid region, and the electron-dense granules are displaced to the periphery of the pyrenoid starch. Mitochondria, endoplasmic reticulum, and ribosomes are not clearly defined in the desiccated state while they are more so in the hydrated condition. Golgi bodies were not observed in either lichen component. Finally, no fine structural basis for indicating an exchange of materials between the alga and fungus was observed except, possibly, the convoluted plasmalemma of the alga.

 


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Last modified 27 October 2005.
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