F. M. Gerola

An Electron Microscopy Study of Leaf Vein Tumours from Maize Plants Experimentally Infected with Maize Rough Dwarf Virus

RIASSUNTONelle neoplasie nervali delle foglie di piante di mais infettate sperimentalmente con il virus del nanismo ruvido, si rilevano varie alterazioni ultrastrutturali, sia nelle cellule in cui si possono osservare particelle di virus, sia nelle cellule mesofillari vicine alle neoplasie nervali.Una delle alterazioni ultrastrutturali piu precoci delle cellule mesofillari consiste nella comparsa di numerose vescicole nella porzione peristromatica dei cloroplasti. La presenza di particelle di virus nelle cellule determina invece alterazioni piu pronunciate, accompagnate probabilmente da uno squilibrio osmotico. Infatti, dapprima i dischi dei grani si rigonfiano e perdono molte volte la loro possibilita di evidenziazione, successivamente avviene la rottura della membrana che delimita i cloroplasti, cosicche grani e lamelle finiscono col degenerare, sparpagliandosi per il citoplasma.Nelle cellule delle neoplasie piu giovani sono facili ad osservarsi particelle « immature » virus-simili, mentre inizia la dif...

Some Observations on the Shape and Localization of Different Viruses in Experimentally Infected Plants, and on the Fine Structure of the Host Cells. II. Nicotiana Glutinosa Systemically Infected with Cucumber Mosaic Virus, Strain y

SUMMARYThe morphological changes induced in leaf cells of Nicotiana glutinosa by CMV-Y have something in common both with those found in virus-infected animals, and with those induced in plants following lacking of mineral elements or mutation.As to the chloroplasts, the alterations are different in leaf areas showing different macroscopical changes. In leaves with mottling the chloroplasts have fragmented lamellae and are often deeply indented. In leaves with chlorotic areas a great number of chloroplasts are exceedingly small, while in dark green areas the chloroplasts contain a number of vesicles and often have ruptured membranes.The tonoplast often disappears, so that the cells become uniformly filled with altered cytoplasmic organelles.The ribosomes are numerous, sometimes aggregated in small groups (infective polysomes?).The Golgi complex gives rise to a great number of vesicles, thus showing an increased activity. The cytoplasm becomes vacuolated and shows masses of membranes often arranged in myel...

Mycoplasma development and cell alterations in white clover affected by clover dwarf an electron microscopy study

SummaryThe presence of mycoplasma has been demonstrated in the phloem of leaves of white clover (Trifolium repens L.) affected by clover dwarf. Mycoplasma-like bodies were found both in parenchyma and companion cells and in sieve elements.In young parenchyma and companion cells mycoplasma-like bodies appeared as round or oval particles with high ribosomal content, delimited by a ribosome-bearing membrane. Their diameter ranged between 50 and 400 nm. In mature sieve elements they were larger, more pleomorphic, and showed a central clear area containing presumed DNA filaments. Budding and dividing forms were sometimes seen among them.The main alterations found in the infected cells were: increased ribosome content, dilation of the perinuclear space, degeneration of mitochondria and chloroplasts, and cytoplasmic vacuolation. Many cells appeared completely disrupted and their content was replaced by a great number of pleomorphic mycoplasma.

Some Observations on the Shape and Localization of Different Viruses in Experimentally Infected Plants, and on the Fine Structure of the Host Cells III: Turnip Yellow Mosaic Virus in Brassica Chinensis L.

SUMMARYAn electron microscopy study has been made on ultrathin sections of leaves from Brassica chinensis experimentally infected with TYMV showing the typical symptoms of the desease.The most prominent alterations have been found in the cells of the whitish leaf areas, where the chloroplasts, shorter and thicker than normal, appear deeply lobated. Portions of these chloroplasts often detach themselves from the chloroplasts and become free in the cytoplasm. The chloroplast membrane invaginates and forms a number of small vesicles all around the chloroplasts. The lamellar system is markedly reduced.A great number of virus-like particles is visible in the cytoplasm. These particles are similar in size and shape to the virus particles isolated from infected plants, and are thought to be TYMV particles.

Some Observations on the Shape and Localization of Different Viruses in Experimentally Infected Plants, and on the Fine Structure of the Host Cells

SUMMARYFragments of leaves from Chenopodium amaranticolor experimentally infected with Arabis mosaic virus have been examined in the electron microscope.In the chlorotic leaf areas, some cells are badly damaged, while others are only slightly altered. Virus particles are seen only in the latter cells.In the less damaged cells the chloroplasts often show protrusions at their ends and seem swollen. Their grana are formed by a reduced number of discs, and the stromatic lamellae are sometimes fragmented. Voluminous cytoplasmic portions with a great number of virus particles are present. These particles have hexagonal shape and a diameter of about 25.5 mμ. They aggregate in concentric layers which form hollow spherical bodies of about 1 μ diameter, inside which is trapped a portion of cytoplasm or a round, electron opaque body. A number of short, bending membranes is frequently seen in these virus-rich cytoplasmic areas.In the more severely damaged cells the chloroplast membrane dissolves, and the chloroplast ...

An electron microscopy study of the penetration of tobacco mosaic virus into leaves following experimental inoculation

Abstract Leaves of Vigna sinensis were inoculated with tobacco mosaic virus (TMV) by gently rubbing their surface with a suspension of virus particles mixed with Carborundum powder. The modifications induced by this treatment on the leaf surface and in the epidermal cells were studied on replicas of the leaf surface and in ultrathin sections of the leaf. On the leaf surface scratchings and a great number of TMV particles were detected; some of the TMV particles were attached to the surface in vertical position. In the epidermal cells, as seen in sections, the external cell wall showed blebs under the cuticle. It is inferred that the rubbing of the leaf surface favors the implantation of some virus particles on the cuticle, and that the alterations of the cell wall provide an easy way of penetration of the particles into the epidermal cells.

An Electron Microscope Study of Different Plants Infected with Grapevine Fanleaf Virus

Abstract The alterations caused by GFV in the leaves and roots of Vitis vinifera, and in the leaves of Nicotiana clevelandii and Chenopodium amaranticolor were studied in the electron microscope. In Nicotiana and Vitis, the main alterations were found in the chloroplasts, while in Chenopodium they were found in the cytoplasm. In all cases, the tonoplast appeared more electron opaque than normal and showed irregular densities over its surface. The presence of virus-like particles was demonstrated only in two cases.

A submicroscopical study of leaves of alfalfa, Basil, and tobacco experimentally infected with lucerne mosaic virus

SummaryThe leaves of three species of plants (Medicago sativa L.,Ocymum basilicum L., andNicotiana tabacum L., cv.Samsun), previously infected with lucerne mosaic virus (LMV), were studied in the electron microscope. In the leaves ofM. sativa andO. basilicum the infection was systemic, while in the leaves ofN. tabacum the infection was local. In all the three species LMV particles were always detected only in the cytoplasm. Apart from the presence of virus particles in the cytoplasm, no ultrastructural alterations were found inM. sativa andN. tabacum. InO. basilicum, the green leaf areas did not show any prominent alterations, while the yellow leaf areas showed marked alterations of the chloroplasts. In these, the lamellar system was scarcely developed, and the few thylakoids tended to fragment, curl and disappear. In the chloroplast stroma, there was an abnormal development of filamentous structures, resembling the stromacentre.

Histological localization of citrus infectious variegation virus (CVV) inPhaseolus vulgaris

SummaryUltrathin sections ofPhaseolus vulgaris leaves were studied in the electron microscope. The leaves were taken from plants, both healthy and experimentally infected with CVV. The sieve tubes and companion cells of all samples contained a slime-like substance, more or less organized into compact systems. In the mature sieve elements of virus-infected plants systems of parallel membranes were seen along which spherical particles, of about 30 mΜ diameter, were aligned in simple rows.

Differences in Septal Pore Apparatus Ultrastructure of Tremella Mesenterica

SUMMARYMany discussions about taxonomic significance of dolipore/parenthe-some ultrastructure have been published, during the last few years. However, the problem is difficult because, in the majority of Basidiomycetes, the real function of the pore cap is undecided. Our research shows that the dolipore/parenthesome ultrastructure of Tremella mesenterica Fries, varies according to its location, either in the secondary micelium hyphae, or at the basidum base, or in the conidiophore hyphae. In addition, the conidiophore hyphae extremities, when dividing to form conidia, form a passage that is always without a parenthesome. This variability suggests that dolipore-/parenthesome morphology is connected with different functions, according to its location.