Structure and Ultrastructure of Three Oak Leaf Galls: L., Geoffroy and Hartig.

The structural and ultrastructural characteristics of galls induced by three species of insects parasitizing on oak leaves ( L.) were examined utilizing light and fluorescent microscopes, as well as scanning and transmission electron microscopes. The tissues of the investigated galls exhibited marked differences from those of a typical oak leaf. In the L. gall, the larval chamber in its final stage was formed from the remnants of dead cells that remained after larval feeding on the gall nutritive tissue. The cells of the gall nutritive tissue and the cells of the gall parenchyma exhibited diametrical differences: the former contained dense cytoplasm and had large nuclei and nucleoli, whereas the latter displayed sparse cytoplasm, prominent vacuoles, and very small nuclei. The region of coalescence between the gall stalk and leaf tissues has been described. In Geoffroy gall, the early developmental phases have been described in detail. The external gall tissues resembled periderm, whereas periderm does not normally occur in leaves. In the cytoplasm of Hartig gall, different bodies were found, including organized smooth endoplasmic reticulum; however, not all of the observed structures were definitively classified.