Electron microscopy of Peach leaves infected by Taphrina deformans (Berk.) Tul

• Published in: Phytopathologia mediterranea 1972-12, Vol.11 (3), p.166-179
• Main Authors: Marte, Mario, Gargiulo, Anna Maria
• Format: Article
• Language: English
• Subjects: Cell walls; Chloroplasts; Cytoplasm; Hyphae; Leaves; Mitochondria; Organelles; Parasite hosts; Parasites; Plant cells
• ISSN: 0031-9465; 1593-2095

Tumourous tissues of Peach leaves infected by Taphrina deformans, both at the beginning of the disease (end of April) and after maturation of the asci (end of May), have been investigated at the electron microscope. During the first phase of the disease the content of infected nuclei becomes more dense and homogeneous than normal. This change slowly decreases in intensity and disappears immediately before death. The hypertrophied cells actively multiply by means of amitotic divisions. The nucleus first loses its envelope and its mass becomes mixed with the surrounding cytoplasm. Then, both nucleus and cytoplasm are partitioned by a septum which, like the mitotic cell plate, originates from the fusion of small electronically empty vesicles covered by a single membrane. The two new nuclei then reacquire an individuality and a new envelope forms around them. At no time during nuclear amitotic scission were microtubules observed. There is a considerable increase in free ribosomes in the cytoplasm of the hypertrophied cells. This phenomenon, that may be correlated with metabolic activation tends to disappear after maturation of the asci, when the cytoplasm appears emptier and more vesiculated than normal. There is a gradual process of regression of the chloroplasts from the first stages of disease onwards. The chloroplasts decrease greatly in volume, lose starch, assume elongated forms and sometimes divide. Their lamellar system is drastically reduced. It was not possible to prove with certainty whether any of the chloroplasts regressed to the status of propias tids. However, it is certain that, by the time cellular necrosis had occurred, the greater part of these organelles had not reached the proplastid stage. Precipitates, dense to electrons and probably formed of polyphenols, were observed in the vacuole of several tumour cells especially during the first phases of infection. With the gradual advance of the disease, granular deposits, very dense to electrons, become evident in the mitochondria, while the matrix of these organelles becomes more opaque and their cristae expand slightly. After maturation of the asci some infected cells appear necrotic. Their cytoplasm becomes more and more vesiculated, concurrent with some activation of the Golgi. The matrices of the mitochondria and plastids become very electron-dense as also do their membranes and that of the endoplasmic reticulum. All these elements are visibly thicker. Finally, the cytoplasm coagulates and