Microscopie de la mycoflore des aiguilles de sapin (Abies alba). II. Lophodermium piceae
Colonization of Abies alba Mill, needles by Lophodermium piceae (Fckl.) Höhn. (Ascomycetes, Hypodermataceae) was studied by light and electron microscopy. Internal mycelium is at first extracellular and invades all the tissues of the needle; thereafter hyphae may penetrate all cells. Cytoplasm and walls of living cells (parenchyma, phloem, cellulosic transfusion tissues) are then lysed. Hyphae also invade thick-walled and lignified cells (epidermis, hypodermis, xylem, tracheids, and fibers of transfusion tissues) without major degradation of the cell wall. Ascomatal development is intraepidermic. Colonization of the needles is limited by black areas (the diaphragms), the structure of which is described. Lophodermium piceae is a primary saprophyte. Needles are colonized during senescence but ascomata appear only on fallen needles. There are about 230 ascomata per gram of needles. The ecology of this fungus is compared with that of Thysanophora penicillioides (Roum.) Kendrick on Abies needles and with that of Lophodermium pinastri (Schrad.) Chev. on Pinus needles.