Dark Green Tissue Research Articles

Proteingehalt in hell- und dunkelgrünen Blattbezirken mosaikkranker Tabakpflanzen

The protein content of yellow green and dark green areas of leaves of tobacco plants systemically infected by tobacco mosaic virus was investigated. The content of total proteins as well as the content of soluble proteins in dark green tissue is higher than in yellow green tissue. From the view of the protein metabolism the yellow, virus-enriched tissue seems to be physiologically older than the dark green tissue in which — at least partially — virus-induced virus inhibitors are active. A disc-electrophoretic separation of the soluble proteins shows only small differences between both types of tissues.

Effects of TYMV infection on growth of Brassica pekinensis Rupr

The effect of turnip yellow mosaic virus (TYMV) infection on the growth of various parts of Chinese cabbage plants was studied in relation to virus synthesis, the production of leaf pigments and various macromolecules. Mild and severe strains of the virus affected overall growth to about the same extent, but growth form and distribution of chlorophyll were affected differently. Among the host components studied, the first to be affected by infection were chlorophyll and Fraction I protein. Late in infection the reduction of ribosomes and proteins on a weight/plant basis was about 20 times greater than the weight of virus produced. Dark green islands of tissue of the mosaic caused by a severe white strain of the virus made a significant contribution to the total chlorophyll of the diseased plant. The proportion of lamina that became dark green tissue in new leaves could be increased by removal of old expanded leaves that had escaped infection.

Inclusions and wall deposits in cells of plants infected with oat necrotic mottle virus

Virus-like particles and two types of inclusion bodies were found in cells of leaves of oats, Avena sativa L., and Canada bluegrass, Poa compressa L., infected with oat necrotic mottle virus. The particles and inclusion bodies were seen in pale green tissue and in most samples of dark green tissue of mottled, mature oat leaves, but were seen only in the pale green tissue of immature leaves. There was also evidence of infection in oat roots.Tubules and (or) vesicles occurred between the cell wall and the plasmalemma (boundary formation) in many mesophyll cells of infected, mature bluegrass and oat leaves. Three types of abnormal deposits, localized, extensive, and fibrillar, also occurred between the wall and the plasmalemma in many of these cells. The extensive and fibrillar deposits were more common in bluegrass than in oats.

Induction of Disease by Viruses, with Special Reference to Turnip Yellow Mosaic Virus

Historically. we can distinguish three phases in the study of disease symptoms induced by viruses. first, from about 1900 to 1935, might be called The Symptom or The Era of Chaos. Hundreds of diseases were described in detail and given names. There was widespread confusion about the dis­ eases and their unknown causative agents. Goldstein (30) was the first to attempt to relate disease patterns to the developmental processes of the plant. She found that the distinctive mosaic patterns in successive leaves of tobacco plants infected with tobacco mosaic virus (TMV) were related to the age of the leaf at the time it became infected. She also noted that dark green tissue appeared cytologically normal. discovery, about 1936, that several plant viruses were ribonucleopro­ teins focussed attention on the virus particles themselves. With the develop­ ment of molecular biology after World War II, the study of virus symptoms fell into general disrepute, as being rather second-grade purely descriptive science. This might be called The Era of Prejudice. Since about 1965 a new trend has begun to emerge. knowledge about the structure and replication of viruses provided by molecular biology allows us to think much more constructively about possible ways in which viruses might induce symptoms; very sensitive and specific analytical procedures have been developed; and the widespread availability of high resolution elec­ tron microscopes has helped to bridge the gap between biochemical knowl­ edge and descriptions of a disease based on macroscopic observation and the light microscope. To understand how a virus causes disease we need to be able to explain, in terms of molecular biology and biochemistry, how a single virus particle con­ taining a piece of genetic material with about 2000 base triplets can infect and cause disease in a growing plant, organized into a variety of tissues and organs with specific structures and functions and containing when mature

On the origin of dark green tissue in tobacco leaves infected with tobacco mosaic virus

In tobacco leaves showing a mosaic pattern caused by tobacco mosaic virus (TMV), yellow green tissue contains large amounts of virus. Dark green tissue contains very low concentrations of virus and appears cytologically normal. Two types of dark green tissue can be distinguished: “true” dark green which remains in this state for the life of the leaf, and “pseudo” dark green in which virus production begins at some late stage in leaf development. True dark green tissue does not appear to be able to support replication of the virus because (1) it is resistant to infection by mechanical means, (2) although the boundary is stable between a dark green area and a yellow green area, the protoplasmic connections between cells containing high and low concentrations of virus appear normal. On the dark green side of such boundaries there is a gradient of decreasing concentration of free virus rods extending laterally for at least several cells into the dark green tissue; such boundaries remain stable for weeks. Dark green areas appear only in leaves which were about 2.4 cm long or smaller at the time they were invaded by virus. The third or fourth leaf above the inoculated leaf is the first to show mosaic under our conditions. In this leaf dark green islands must have arisen, at the time of virus invasion, from clusters of several hundred cells extending through all histological layers of the lamina. Clusters of this size could not have arisen by chance. Therefore, some as yet unidentified diffusible agent must be involved in the formation of these clusters.

Role of virus strains and leaf ontogeny in the production of mosaic patterns by turnip yellow mosaic virus

The production of islands of different types of tissue containing virus in Chinese cabbage plants systemically infected with TYMV is dependent on the existence of various strains of the virus which are present in the inoculum or arise by mutation in the plant. Different virus strains which cause recognizably distinct pathological changes in the chloroplasts are localized in various islands of tissue. Examination by light microscopy shows that in many parts of a leaf showing a macroscopic mosaic there is also a microscopic mosaic in which different cell layers within the leaf are affected differently by the virus. The close parallels between the distribution of cell types in TYMV infection and in leaves containing plastid mutants lend support to the view that the various islands of tissue in the mosaic induced by TYMV represent clones of cells originating from a dividing cell infected by a single strain of virus. Disks of dark green tissue from leaves showing mosaic and floated on water or various media did not produce virus, but were capable of massive synthesis of 83 S ribosomes under the influence of kinetin.