Barrier zone formation in host and nonhost trees inoculated with Ophiostoma ulmi. II. Ultrastructure

1991 ◽  
Vol 69 (9) ◽  
pp. 2074-2083 ◽  
Author(s):  
Danny Rioux ◽  
G. B. Ouellette
Keyword(s):  
Electron Microscopy ◽  
Dutch Elm Disease ◽  
Populus Balsamifera ◽  
Ulmus Americana ◽  
Light Microscope Level ◽  
Zone Formation ◽  
Ophiostoma Ulmi ◽  
Transmission Electron ◽  
Histochemical Tests ◽  
Barrier Zone

Barrier zone formation was studied in annual shoots and small branches of Ulmus americana L., Prunus pensylvanica L.f., and Populus balsamifera L. following inoculation with Ophiostoma ulmi (Buism.) Nannf. Ultrastructural observations showed that electron-opaque compounds, which usually were identified as containing phenolics by previous histochemical tests, were often present within cells of this tissue. Many lipidic globules were also observed within some barrier zone cells of Populus balsamifera. Additional wall layers, suberized or not, were frequently observed in these barrier zone cells. When histochemical tests for suberin at the light microscope level were strongly positive, the lamellation typical of suberin was evident in transmission electron microscopy. Gum canal formation in Prunus pensylvanica was found to be initiated and the canals widened predominantly by a lysogenous process. Key words: Dutch elm disease, nonhost plants, Ophiostoma ulmi, Ulmus americana, ultrastructure, gum canals, suberized layers.

Barrier zone formation in host and nonhost trees inoculated with Ophiostoma ulmi. I. Anatomy and histochemistry

1991 ◽  
Vol 69 (9) ◽  
pp. 2055-2073 ◽  
Author(s):  
Danny Rioux ◽  
G. B. Ouellette
Keyword(s):  
Principal Component ◽  
Dutch Elm Disease ◽  
Populus Balsamifera ◽  
Ulmus Americana ◽  
Zone Formation ◽  
Ophiostoma Ulmi ◽  
Parenchyma Cells ◽  
Zone Cell ◽  
Histochemical Tests ◽  
Barrier Zone

Barrier zone formation was studied in small branches of Ulmus americana L., Prunus pensylvanica L.f., and Populus balsamifera L. following inoculation with Ophiostoma ulmi (Buism.) Nannf. (the Dutch elm disease pathogen). Barrier zones were continuous in the nonhosts whereas they were generally discontinuous in U. americana; barrier zone formation also occurred at a later stage of infection in the latter than in the former. Barrier zones were formed of parenchyma cells and fibers in U. americana, mainly of parenchyma cells in Prunus pensylvanica, and of fibers in Populus balsamifera. Fibers as a principal component of barrier zones are described for the first time. Histochemical tests revealed that the proportion of lignin was higher in barrier zone cell walls than in elements of the noninvaded xylem. Barrier zones contained suberized cells, the number of which was progressively greater in the order U. americana, Prunus pensylvanica, and Populus balsamifera. However, many fibers of U. americana occasionally formed a continuous barrier zone and had an internal layer that was slightly suberized. In addition, phenolic compounds were usually detected within barrier zone cells of these species. Key words: Dutch elm disease, nonhost plants, Ophiostoma ulmi, Ulmus americana, anatomy, histochemistry.

Light microscope observations of histological changes induced by Ophiostoma ulmi in various nonhost trees and shrubs

1989 ◽  
Vol 67 (8) ◽  
pp. 2335-2351 ◽  
Author(s):  
Danny Rioux ◽  
G. B. Ouellette
Keyword(s):  
Dutch Elm Disease ◽  
Populus Balsamifera ◽  
Class Iii ◽  
Shrub Species ◽  
Histological Changes ◽  
Zone Formation ◽  
Ophiostoma Ulmi ◽  
Parenchyma Cells ◽  
Barrier Zone ◽  
Trees And Shrubs

Ophiostoma ulmi (the Dutch elm disease pathogen) was inoculated into 13 nonhost tree and shrub species. Four classes were recognized based on their susceptibility to this pathogen. In Prunus pensylvanica (class I), bubbles formed in vessel members within 3 days after inoculation, and gels formed 5 days later. At day 5, the vascular cambium covering the colonized zone became altered. A barrier zone was formed in 60% of the inoculated twigs. When twigs wilted, the vessels around the twig were occluded, and barrier zone formation was partial. In Populus balsamifera (class II), tyloses formed in vessels of invaded xylem within 8 days after inoculation followed by accumulation of compounds suspected to be phenolics in parenchyma cells. Barrier zone formation occurred in 66% of the inoculated twigs. In Sorbus americana (class III), a pronounced dark discoloration developed rapidly in the invaded xylem. Sparse gels and O. ulmi cells were present in vessel members. Gel formation was limited to vessels that were adjacent to parenchyma cells. Pit membranes of bordered and half-bordered pit pairs became thicker and more darkly stained than in controls. These observations suggest that the first steps of pathogenesis are induced by the action of harmful metabolites of O. ulmi. Few noticeable changes occurred in the species of class IV.

Barrier Zone Formation as a Resistance Mechanism of Elms to Dutch Elm Disease

IAWA Journal ◽  
1985 ◽  
Vol 6 (1) ◽  
pp. 71-77 ◽  
Author(s):  
K.J.M. Bonsen ◽  
R.J. Scheffer ◽  
D.M. Elgersma
Keyword(s):  
Time Course ◽  
Resistance Mechanism ◽  
Dutch Elm Disease ◽  
Host Responses ◽  
Moderate Degree ◽  
Zone Formation ◽  
Ophiostoma Ulmi ◽  
Time Course Study ◽  
High Degree ◽  
Barrier Zone

Host responses of elms susceptible and resistant to Dutch elm disease were histologically examined. In a time course study the susceptible elm clone Ulmus × hollandica 'Belgica' and U. × hollandica '390', a clone which shows a high degree of resistance to non-aggressive isolates and a moderate degree of resistance to aggressive isolates of Ophiostoma ulmi, were inoculated in twig or trunk with either an aggressive or a non-aggressive isolate of O. ulmi. For purposes of comparison, the susceptible elm U. americana and the more resistant clones U. × hollandica 'Groeneveld', U. 'Lobel' and U. 'Sapporo Autumn Gold' were included. Depending on clone-isolate compatibility, infected twigs reacted by a walling off process, by barrier zone formation, or failed to resist the infection and died. Trees inoculated into the trunk reacted comparably but in the case of a compatible combination they always formed a barrier zone and the cambium never died in the year of inoculation.

scholarly journals Fungal Colonization and Host Defense Reactions in Ulmus americana Callus Cultures Inoculated with Ophiostoma novo-ulmi

2009 ◽  
Vol 99 (6) ◽  
pp. 642-650 ◽  
Author(s):  
Mirella Aoun ◽  
Danny Rioux ◽  
Marie Simard ◽  
Louis Bernier
Keyword(s):  
Electron Microscopy ◽  
Quantitative Polymerase Chain Reaction ◽  
Callus Cultures ◽  
Dutch Elm Disease ◽  
Fungal Colonization ◽  
Ulmus Americana ◽  
In Vitro System ◽  
Transmission Electron ◽  
Callus Tissues

The host–pathogen interaction leading to Dutch elm disease was analyzed using histo- and cyto-chemical tests in an in vitro system. Friable and hard susceptible Ulmus americana callus cultures were inoculated with the highly aggressive pathogen Ophiostoma novo-ulmi. Inoculated callus tissues were compared with water-treated callus tissues and studied with light microscopy (LM), transmission-electron microscopy (TEM), and scanning-electron microscopy (SEM). New aspects of this interaction are described. These include the histological observation, for the first time in plant callus cultures, of suberin with its typical lamellar structure in TEM and the intracellular presence of O. novo-ulmi. Expression of the phenylalanine ammonia lyase gene, monitored by real-time quantitative polymerase chain reaction, was correlated with the accumulation of suberin, phenols, and lignin in infected callus cultures. This study validates the potential use of the in vitro system for genomic analyses aimed at identifying genes expressed during the interaction in the Dutch elm disease pathosystem.

Precipitation in Al-Li-Cu Alloys

1981 ◽  
Vol 39 ◽  
pp. 44-45
Author(s):  
J. E. O'Neal ◽  
K. K. Sankaran
Keyword(s):  
Electron Microscopy ◽  
Age Hardening ◽  
Precipitation Behavior ◽  
Zone Formation ◽  
Specific Strength ◽  
Hardening Behavior ◽  
Cu Alloys ◽  
High Specific Strength ◽  
Transmission Electron ◽  
Structural Applications

Al-Li-Cu alloys combine high specific strength and high specific modulus and are potential candidates for aircraft structural applications. As part of an effort to optimize Al-Li-Cu alloys for specific applications, precipitation in these alloys was studied for a range of compositions, and the mechanical behavior was correlated with the microstructures.Alloys with nominal compositions of Al-4Cu-2Li-0.2Zr, Al-2.5Cu-2.5Li-0.2Zr, and Al-l.5Cu-2.5Li-0.5Mn were argon-atomized into powder at solidification rates ≈ 103°C/s. Powders were consolidated into bar stock by vacuum pressing and extruding at 400°C. Alloy specimens were solution annealed at 530°C and aged at temperatures up to 250°C, and the resultant precipitation was studied by transmission electron microscopy (TEM).The low-temperature (≲100°C) precipitation behavior of the Al-4Cu-2Li-0.2Zr alloy is a combination of the separate precipitation behaviors of Al-Cu and Al-Li alloys. The age-hardening behavior at these temperatures is characteristic of Guinier-Preston (GP) zone formation, with additional strengthening resulting from the coherent precipitation of δ’ (Al3Li, Ll2 structure), the presence of which is revealed by the selected-area diffraction pattern (SADP) shown in Figure la.

Fine structure and possible functions of the hermaphrodite duct of some pulmonate snails (Mollusca: Gastropoda)

1990 ◽  
Vol 48 (3) ◽  
pp. 68-69
Author(s):  
Alan N. Hodgson
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Fine Structure ◽  
Seminal Vesicle ◽  
Reproductive Biology ◽  
Light Microscope ◽  
Light Microscope Level ◽  
Transmission Electron ◽  
Standard Techniques

The hermaphrodite duct of pulmonate snails connects the ovotestis to the fertilization pouch. The duct is typically divided into three zones; aproximal duct which leaves the ovotestis, the middle duct (seminal vesicle) and the distal ovotestis duct. The seminal vesicle forms the major portion of the duct and is thought to store sperm prior to copulation. In addition the duct may also play a role in sperm maturation and degredation. Although the structure of the seminal vesicle has been described for a number of snails at the light microscope level there appear to be only two descriptions of the ultrastructure of this tissue. Clearly if the role of the hermaphrodite duct in the reproductive biology of pulmonatesis to be understood, knowledge of its fine structure is required.Hermaphrodite ducts, both containing and lacking sperm, of species of the terrestrial pulmonate genera Sphincterochila, Levantina, and Helix and the marine pulmonate genus Siphonaria were prepared for transmission electron microscopy by standard techniques.

Combined Use of Small Angle Neutron Scattering (Sans) and (Conventional and High Resolution) Electron Microscopy for the Characterization of Early Stages of Ordering and Phase Separation in Ni-Ti

1986 ◽  
Vol 82 ◽  
Author(s):  
A. Cerri ◽  
R. Schmelczer ◽  
P. Schwander ◽  
G. Kostorz ◽  
A.F. Wright
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Tem Analysis ◽  
Zone Formation ◽  
Early Stages ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Combined Use ◽  
Integrated Intensity

ABSTRACTThe decomposition of Ni ∼ 11.5 at.% Ti single crystals was studied for an ageing temperature of 540°C. In this alloy, coherent ordered zones of γ′-Ni3Ti (Cu3Au structure) are formed prior to the stable n precipitates. The early stages of zone formation were investigated by in-beam SANS and transmission electron microscopy (TEM). Electron diffraction, high resolution electron microscopy, TEM analysis of dislocation arrangements in samples deformed after ageing and X-ray measurements of the integrated intensity at L12 superstructure positions show that ordered regions already appear in quenched samples, whereas compositional changes, as determined by SANS measurements, occur only upon ageing.

Accumulation of mansonones in callus cultures of Ulmus americana L. in the absence of a fungal-derived elicitor

1997 ◽  
Vol 75 (3) ◽  
pp. 513-517 ◽  
Author(s):  
F. G. Meier ◽  
W. R. Remphrey
Keyword(s):  
Culture Media ◽  
Fungal Growth ◽  
Callus Cultures ◽  
Dutch Elm Disease ◽  
Ulmus Americana ◽  
Ophiostoma Ulmi ◽  
Medium Components ◽  
Tissue Culture Media ◽  
Wound Reaction ◽  
Accumulation Ability

The Dutch elm disease pathogens Ophiostoma ulmi (Buism.) Nannf. and Ophiostoma novo-ulmi Brasier elicit the production of phytoalexins called mansonones in the American elm (Ulmus americana L.). As part of a larger investigation, it was revealed that mansonone elicitation in callus culture does not require the Dutch elm disease pathogens, as has been reported in other studies. The objective of this study was to determine the nature and timing of the nonfungal elicited mansonone accumulation in U. americana callus. Initially, 7-week-old calli were subjected to inoculations with various fungal growth medium components. Mansonone production occurred in all treatments, indicating that it was stimulated prior to the addition of the medium components. Next, cotyledons and calli at various stages of development were analysed for the production of mansonones to determine the timing of its production. Mansonone production appeared to be correlated with the initiation of callus production and may be related to the callus wound reaction. As the callus aged, its colour changed from white–green to brown possibly as a result of phytoalexin accumulation. Additional experiments in which the cotyledon source, agar source, and type of plant tissue culture media were modified resulted in no change to the mansonone accumulation ability of the callus. The discrepancy between our results and those of other researchers could be due to differences in the method of mansonone quantification, namely, that our method is more sensitive and led to the detection of mansonones where previously none had been found. Further research must be done in this area to investigate this mansonone accumulation. Key words: phytoalexin, Dutch elm disease, mansonone, Ulmus americana, callus.

The structure and possible function of the ventral papillae of Notocotylus triserialis Diesing, 1839

Parasitology ◽  
1982 ◽  
Vol 84 (2) ◽  
pp. 313-332 ◽  
Author(s):  
Barbara M. MacKinnon
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Alkaline Phosphatase ◽  
Ventral Surface ◽  
Acid Mucopolysaccharide ◽  
Acid And Alkaline Phosphatase ◽  
Transmission Electron ◽  
Histochemical Tests ◽  
Pyriform Cells

SUMMARYNotocotylus triserialis bears three rows of eversible papillae on its ventral surface. These papillae, which in living worms are firmly applied to the host mucosa, contain numerous pyriform cells. Histochemical tests indicate the presence, within the papillar cells, of protein, lipid, haemoglobin and esterase, and the absence of carbohydrate, acid mucopolysaccharide, RNA, haemosiderin and acid and alkaline phosphatase. Transmission electron microscopy shows the tegument of the papillae to be similar to the non-papillar ventral tegument. The pyriform cells contain many mitochondria with numerous cristae. A mechanism is proposed whereby the musculature of the worm effects the retraction and eversion of the ventral papillae.

scholarly journals Variation in Response of Selected American Elm Clones to Ophiostoma ulmi

1995 ◽  
Vol 13 (3) ◽  
pp. 126-128 ◽  
Author(s):  
A.M. Townsend ◽  
S.E. Bentz ◽  
G.R. Johnson
Keyword(s):  
Dutch Elm Disease ◽  
Main Trunk ◽  
Ulmus Americana ◽  
Disease Symptoms ◽  
Ophiostoma Ulmi ◽  
American Elm ◽  
Causal Fungus ◽  
One Year ◽  
Crown Dieback ◽  
High Degree

Abstract Ramets of nine American elm (Ulmus americana L.) clones or cultivars were planted with ramets of Ulmus ‘Frontier’, Ulmus ‘Prospector’, and American elm seedlings in a randomized block, split-plot design. When they were three years old, the trees were inoculated in the main trunk on either one of two selected dates in May with a spore suspension of Ophiostoma ulmi, the causal fungus for Dutch elm disease (DED). Analyses of variance showed significant variation among clones and between inoculation dates in disease symptoms four weeks and one year after inoculation. Inoculations made on May 18 generally created significantly more symptoms than inoculations made only nine days later. Four-week symptom expression was influenced also by a significant interaction between clonal or seedling group and inoculation date. When data from both inoculation dates were combined, six American elm clones (‘American Liberty’, ‘Princeton’, 680, R18–2, 180, and 3) showed significantly fewer foliar symptoms after four weeks than the American elm seedlings and three other American elm clones. Five of these same six more tolerant American clones averaged significantly less crown dieback after one year than the other American clones or seedlings tested. One of the American elm clones (clone 3) showed a level of disease tolerance equal statistically to ‘Frontier’ and ‘Prospector’, two cultivars which have shown a high degree of tolerance to DED in other studies.

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