Chioroplast-ultrastructure and chlorophyll contení in leaves from Quercus branches with and without epiphytic lichen thalli

The effect that the massive presence of lichen thalli growing on the branches of Quercus pyrenaica and Q. rotundifolia leaves has on their chloroplasts been studied. In both species there were significant decreases in the amount of chlorophylls in the leaves of twigs with a dense cover of lichens in comparison with the leaves from thallus-free twigs. The áreas and perimeter of chloroplasts in leaves from twigs with epiphytes did not differ significantly from those in leaves without epiphytes. However, in leaves with epiphytes the percentage of chloroplast área occupied by starch was higher. In Q. pyrenaica the number of grana per chloroplast section and per //in2, the percentage of chloroplast stroma occupied by grana, the average number of thylakoids forming grana and the grana width was significantly smaller in leaves near lichen populations. These results are discussed and related to the great chelating capacity of the lichen's substances.