Ultrastructural aspects of Pyrola mycorrhizae

1985 ◽  
Vol 63 (6) ◽  
pp. 1089-1098 ◽  
Author(s):  
Diane C. Robertson ◽  
Jack A. Robertson
Keyword(s):  
Epidermal Cell ◽  
Matrix Material ◽  
Root Surface ◽  
Root Tip ◽  
Host Cytoplasm ◽  
Hartig Net ◽  
Arbutoid Mycorrhizae ◽  
Fungal Hyphae ◽  
Host Origin ◽  
Electron Microscopes

The mycorrhizae of six species of Pyrola were examined with light and electron microscopes. The hyphae on the root surface varied from a loose weft to an abundant mass with numerous strands, but no organized sheath was observed. Infection began with the formation of a Hartig net several millimetres behind the root tip. Hyphae from this net subsequently grew into each epidermal cell, forming masses of intracellular hyphae. These hyphae were surrounded by the host plasmalemma and a matrix material, presumably of host origin. During the stage of mature infection the host cytoplasm was finely granular and filled with organelles. The host vacuoles often had tanninlike deposits along their tonoplasts. Senescence of the symbiosis began with the gradual degeneration of the host cytoplasm, which became dark and vesiculated with loss of its organelles. The fungal hyphae and matrix material appeared essentially unchanged at this stage but eventually degenerated and collapsed. The fungal partners were normally basidiomycetes with dolipore septa, but one ascomycetous infection (distinguished by simple septa and Woronin bodies) was found to have a similar mycorrhizal organization. It differed in having an intermittent Hartig net. The presence of both the Hartig net and intracellular hyphae indicates that these are arbutoid mycorrhizae.

Structure and ontogeny of Alnus crispa – Alpova diplophloeus ectomycorrhizae

1986 ◽  
Vol 64 (1) ◽  
pp. 177-192 ◽  
Author(s):  
H. B. Massicotte ◽  
R. L. Peterson ◽  
C. A. Ackerley ◽  
Y. Piché
Keyword(s):  
Structural Changes ◽  
Hyphal Growth ◽  
Root Surface ◽  
Epidermal Cells ◽  
Transfer Cells ◽  
Wall Ingrowths ◽  
Alnus Crispa ◽  
Hartig Net ◽  
Fungal Hyphae ◽  
Branching System

Alnus crispa (Ait.) Pursh seedlings were grown in plastic pouches and inoculated with Frankia to induce nodules and subsequently with Alpova diplophloeus (Zeller & Dodge) Trappe & Smith to form ectomycorrhizae. The earliest events in ectomycorrhiza formation involved contact of the root surface by hyphae, hyphal proliferation to form a thin mantle, and further hyphal growth to form a thick mantle. Structural changes in the host, the mycosymbiont, and the fungus–epidermis interface were described at various stages in the ontogeny of ectomycorrhizae. Fungal hyphae in contact with epidermal cells in the regions of intercellular penetration and paraepidermal Hartig net developed numerous rough endoplastic reticulum cisternae. In more proximal regions of the mycorrhiza, these gradually became fewer in number and smooth. A complicated labyrinthine wall branching system also developed in the fungus in these regions. Concurrently, epidermal cells formed wall ingrowths in regions adjacent to Hartig net hyphae. There was a gradient in the formation of these epidermal transfer cells as the mycorrhiza developed, and an additional deposition of secondary cell wall over the wall ingrowths occurred as transfer cells senesced. Nonmycorrhizal control roots did not develop epidermal wall ingrowths. Electron-dense material, which was also autofluorescent, was deposited in the outer tangential walls of the exodermis contiguous to the paraepidermal Hartig net.

Structure and ontogeny of Betula alleghaniensis – Pisolithus tinctorius ectomycorrhizae

1990 ◽  
Vol 68 (3) ◽  
pp. 579-593 ◽  
Author(s):  
H. B. Massicotte ◽  
R. L. Peterson ◽  
C. A. Ackerley ◽  
L. H. Melville
Keyword(s):  
Root Hairs ◽  
Root Surface ◽  
Pisolithus Tinctorius ◽  
Initial Contact ◽  
Broad Host Range ◽  
Betula Alleghaniensis ◽  
Cortical Cells ◽  
Structural Modifications ◽  
Hartig Net ◽  
Primary Roots

The ontogeny and ultrastructure of ectomycorrhizae synthesized between Betula alleghaniensis (yellow birch) and Pisolithus tinctorius, a broad host range fungus, were studied to determine the structural modifications in both symbionts during ectomycorrhiza establishment. A number of stages, including initial contact of hyphae with the root surface, early mantle formation, and mature mantle formation, were distinguished. Interactions between hyphae and root hairs were frequent. As a paraepidermal Hartig net developed, root epidermal cells elongated in a radial direction, but wall ingrowths were not formed. Repeated branching of Hartig net hyphae resulted in extensive fine branches and the compartmentalization of hyphal cytoplasm. Nuclei and elongated mitochondria were frequently located in the narrow cytoplasmic compartments, and [Formula: see text] thickenings developed along walls of cortical cells in primary roots.

scholarly journals A Novel Class of Ectomycorrhiza-Regulated Cell Wall Polypeptides in Pisolithus tinctorius

1999 ◽  
Vol 12 (10) ◽  
pp. 862-871 ◽  
Author(s):  
Pascal Laurent ◽  
Catherine Voiblet ◽  
Denis Tagu ◽  
Dulcinéia de Carvalho ◽  
Uwe Nehls ◽  
...  
Keyword(s):  
Cell Wall ◽  
Cell Adhesion ◽  
Polyacrylamide Gel Electrophoresis ◽  
State Level ◽  
Root Surface ◽  
Pisolithus Tinctorius ◽  
Surface Proteins ◽  
Ectomycorrhizal Symbiosis ◽  
Fungal Cell ◽  
Fungal Hyphae

Development of the ectomycorrhizal symbiosis leads to the aggregation of fungal hyphae to form the mantle. To identify cell surface proteins involved in this developmental step, changes in the biosynthesis of fungal cell wall proteins were examined in Eucalyptus globulus-Pisolithus tinctorius ectomycorrhizas by two-dimensional polyacrylamide gel electrophoresis. Enhanced synthesis of several immunologically related fungal 31- and 32-kDa polypeptides, so-called symbiosis-regulated acidic polypeptides (SRAPs), was observed. Peptide sequences of SRAP32d were obtained after trypsin digestion. These peptides were found in the predicted sequence of six closely related fungal cDNAs coding for ectomycorrhiza up-regulated transcripts. The PtSRAP32 cDNAs represented about 10% of the differentially expressed cDNAs in ectomycorrhiza and are predicted to encode alanine-rich proteins of 28.2 kDa. There are no sequence homologies between SRAPs and previously identified proteins, but they contain the Arg-Gly-Asp (RGD) motif found in cell-adhesion proteins. SRAPs were observed on the hyphal surface by immunoelectron microscopy. They were also found in the host cell wall when P. tinctorius attached to the root surface. RNA blot analysis showed that the steady-state level of PtSRAP32 transcripts exhibited a drastic up-regulation when fungal hyphae form the mantle. These results suggest that SRAPs may form part of a cell-cell adhesion system needed for aggregation of hyphae in ectomycorrhizas.

Genomic in situ hybridization to sectioned nuclei shows chromosome domains in grass hybrids

1990 ◽  
Vol 95 (3) ◽  
pp. 335-341
Author(s):  
A.R. Leitch ◽  
W. Mosgoller ◽  
T. Schwarzacher ◽  
M.D. Bennett ◽  
J.S. Heslop-Harrison
Keyword(s):  
In Situ Hybridization ◽  
Genomic Dna ◽  
Microscope Level ◽  
Hordeum Chilense ◽  
Root Tip ◽  
Interphase Nuclei ◽  
Light Microscope Level ◽  
Thin Sections ◽  
Electron Microscopes

In situ hybridization using biotinylated total genomic DNA and avidin detection systems was adapted for examination of thin-sectioned plant material in the light and electron microscopes. Root tip material was preserved prior to sectioning, so that the in vivo disposition of the chromatin was maintained. Use of total genomic DNA from Secale africanum as a probe enabled the chromatin from the two parental genomes in the grass hybrid Hordeum chilense × S. africanum to be distinguished. The biotinylated probe preferentially labelled the chromosomes of S. africanum origin. DNA-DNA hybrids were visualized at the light-microscope level by Texas Red fluorescence and at the electron-microscope level by the enzymic precipitation of DAB (diaminobenzidine) or by colloidal gold particles. The use of thin sections allowed the location of probe hybridization to be established unequivocally in both metaphase and interphase nuclei. Analysis of interphase nuclei showed that chromatin originating from the two parental genomes did not intermix but occupied distinct domains.

FACTORS GOVERNING ZOOSPORE RESPONSES OF PHYTOPHTHORA MEGASPERMA VAR. SOJAE TO PLANT ROOTS

1967 ◽  
Vol 45 (11) ◽  
pp. 1983-1994 ◽  
Author(s):  
H. H. Ho ◽  
C. J. Hickman
Keyword(s):  
Root Exudate ◽  
Chemical Nature ◽  
Root Surface ◽  
Plant Roots ◽  
Root Tip ◽  
Phytophthora Megasperma ◽  
Negative Pole ◽  
New Feature ◽  
Germ Tubes ◽  
Cyst Germination

In the presence of plant roots, zoospores of Phytophthora megasperma var. sojae reacted in general as do other fungal zoospores: they were attracted to, and trapped in the immediate vicinity of the root surface, on which they encysted rapidly. Encysted zoospores formed a continuous sheath around the root, thickest just behind the root tip. Cyst germination was stimulated. Germ tubes were always initiated from the side of cysts closest to the root and grew towards it. In addition, a new feature was observed, suppression of repeated emergence of zoospores. Zoospore accumulation was nonspecific with respect to host and non-host, resistance, and susceptibility.Tests with exudates and extracts from roots of resistant and susceptible soybean varieties and a non-host, pea, confirmed the chemical nature of the stimulus inducing these responses. Zoospores observed in an electric field were not attracted towards either pole, but they were trapped and encysted rapidly around the negative pole. Cyst germination was not stimulated. Nevertheless, since encystment was more pronounced on root exudate agar mounted on the negative pole, electric charges on roots may also contribute to inducing early encystment of zoospores there.In an investigation of ions on zoospore responses, with ionic resins, all phases of zoospore response to roots, with the exception of attraction, occurred in the presence of hydrogen resin particles.

The root–fungus interface as an indicator of symbiont interaction in ectomycorrhizae

1987 ◽  
Vol 17 (8) ◽  
pp. 846-854 ◽  
Author(s):  
H. B. Massicotte ◽  
C. A. Ackerley ◽  
R. L. Peterson
Keyword(s):  
Cell Wall ◽  
Epidermal Cell ◽  
Apical Meristem ◽  
Epidermal Cells ◽  
Wall Ingrowths ◽  
Wall Ingrowth ◽  
Hartig Net ◽  
Epidermal Cell Wall ◽  
Different Strains ◽  
Cell Wall Ingrowths

Seedlings of Alnuscrispa (Ait.) Pursh, Alnusrubra Bong., Eucalyptuspilularis Sm., and Betulaalleghaniensis Britt. were grown in plastic pouches and subsequently inoculated with Alpovadiplophloeus (Zeller & Dodge) Trappe & Smith (two different strains), Pisolithustinctorius (Pers.) Coker & Couch, and Laccariabicolor (R. Mre) Orton, respectively, to form ectomycorrhizae insitu. Alnus seedlings were inoculated with Frankia prior to inoculation with the mycosymbiont. The interface established between A. crispa and A. diplophloeus was complex, involving wall ingrowth formation in root epidermal cells and infoldings in Hartig net hyphae. Alnusrubra – A. diplophloeus ectomycorrhizae had an interface lacking epidermal cell wall ingrowths but with infoldings in Hartig net hyphae. The interface between E. pilularis –. tinctorius consisted of branching Hartig net hyphae between radially enlarged epidermal cells lacking wall ingrowths. Ectomycorrhizae between B. alleghaniensis and L. bicolor developed unique interfaces with radially enlarged epidermal cells near the apical meristem, which synthesized dense vacuolar deposits. Very fine branchings occurred in Hartig net hyphae.

Interactions between a fungal endophyte and gametophyte cells in Psilotum nudum

1981 ◽  
Vol 59 (5) ◽  
pp. 711-720 ◽  
Author(s):  
R. L. Peterson ◽  
Melanie J. Howarth ◽  
Dean P. Whittier
Keyword(s):  
Energy Source ◽  
Endophytic Fungus ◽  
Cell Walls ◽  
Fungal Endophyte ◽  
Hyphal Cell ◽  
Cell Organelles ◽  
Host Cytoplasm ◽  
Psilotum Nudum ◽  
Parenchyma Cells ◽  
Fungal Hyphae

Mature Psilotum gametophytes found in greenhouse pots containing plants of Hoya, Philodendron, Aspidistra, or Diffenbachia were processed for microscopy. An endophytic fungus was abundant in the rhizoids and in most cortical parenchyma cells except at the growing apices. Although the fungus has not been identified, it is an aseptate fungus with coarse hyphae which occasionally form vesicles. Endophytic fungal hyphae store quantities of lipid which appear to be released into the host cytoplasm upon fungal degeneration. This lipid and the remnants of hyphal cell walls may be used as an energy source by the achlorophyllous gametophyte. Gametophyte cell organelles, including the nucleus, appear to degenerate after fungal breakdown, and the cells presumably die. Although reinfection of cells containing degenerated hyphae was found, it was not particularly common.

scholarly journals 470 Narrow-sense Heritability Estimates for Melon Root Traits

HortScience ◽  
2000 ◽  
Vol 35 (3) ◽  
pp. 475A-475
Author(s):  
Kevin M. Crosby
Keyword(s):  
Genetic Variation ◽  
Root System ◽  
Block Design ◽  
Root Systems ◽  
Root Surface ◽  
Root Tip ◽  
Root Surface Area ◽  
Narrow Sense ◽  
Narrow Sense Heritability ◽  
Heritability Estimates

Improving melon root systems by traditional breeding is one component of the program to develop multiple-stress-resistant melons at the Texas Agricultural Experiment Station, Weslaco. Ten diverse melon lines representing four horticultural groups were intercrossed utilizing a Design II mating scheme. The male parents were: `PI 403994,' `Perlita,' `Doublon,' `Caravelle', and `PI 525106.' The female parents were: `Créme de Menthe,' `Magnum 45,' `BSK,' `PI 124111 × TDI', and `Deltex.' F1 progeny were grown in pasteurized sand in the greenhouse using a randomized complete-block design with four reps. After 4 weeks, root systems from all plants were carefully washed to remove the sand. Each root system was then placed onto a glass, plated, and scanned into the computer software Rhizo Pro 3.8 (Regent Instruments, Quebec). This software calculated root lengths of various diameter classes, root area, and root tip number. All data was input into Agrobase software for calculation of genetic variances based on Design II analysis. Significant differences of contributions by male parents to progeny variation were few. Only length of roots with 1.0- to 1.5-mm-diameter and vine length were significantly different. Differences in contributions by female parents to all traits except root tip number were highly significant. No significant interaction effects were observed for any trait. Narrow-sense heritability estimates were moderate to high for all traits. The range was from 0.56 for root tip number by males to 0.81 for both length of 0.5- to 1.0-mm-diameter roots and vine length for females. Estimates for total root length (0.76) and root surface area (0.77) were high. The lack of male by female interaction suggests very low dominance genetic variation and contributed to high heritability estimates, which represent predominantly additive gene action. Additive genetic variation allows more-efficient progress by selection, making the potential for root system improvement favorable.

scholarly journals Supra-physiological levels of Gibberellins/DELLAs alter the patterning, morphology and abundance of root hairs in root tips of A. thaliana seedlings

2021 ◽  
Author(s):  
Iva McCarthy-Suarez
Keyword(s):  
Gene Expression ◽  
Cell Fate ◽  
Epidermal Cell ◽  
Root Hair ◽  
Root Hairs ◽  
Root Tip ◽  
Spatial Patterning ◽  
Root Tips ◽  
Root Epidermis

In spite of the known role of gibberellins (GAs), and of their antagonistic proteins, the DELLAs, in leaf hair production, no investigations, however, have assessed their hypothetical function in the production of root hairs. To this aim, the effects of supra-physiological levels of GAs/DELLAs on the spatial patterning of gene expression of the root hair (CPC) and root non-hair (GL2, EGL3 and WER) epidermal cell fate markers, as well as on the distribution, morphology and abundance of root hairs, were studied in root tips of 5-day-old A. thaliana seedlings. Results showed that excessive levels of GAs/DELLAs impaired the spatial patterning of gene expression of the root hair/non-hair epidermal cell fate markers, as well as the arrangement, shape and frequency of root hairs, giving rise to ectopic hairs and ectopic non-hairs, two-haired cells, two-tipped hairs, branched hairs, longer and denser hairs near the root tip under excessive DELLAs, and shorter and scarcer hairs near the root tip under excessive GAs. However, when the gai-1 (GA-insensitive-1) DELLA mutant protein was specifically over-expressed at the root epidermis, no changes in the patterning or abundance of root hairs occurred. Thus, these results suggest that, in seedlings of A. thaliana, the GAs/DELLAs might have a role in regulating the patterning, morphology and abundance of root hairs by acting from the sub-epidermal tissues of the root.

Structure of ectomycorrhizae formed by Wilcoxina mikolae var. mikolae with Picea mariana and Betula alleghaniensis

1991 ◽  
Vol 69 (10) ◽  
pp. 2149-2157 ◽  
Author(s):  
Pamela F. Scales ◽  
R. L. Peterson
Keyword(s):  
Electron Microscopy ◽  
Picea Mariana ◽  
Lateral Roots ◽  
Root Apex ◽  
Root Surface ◽  
Betula Alleghaniensis ◽  
Oblique Angle ◽  
Hartig Net ◽  
Wilcoxina Mikolae ◽  
Scanning Electron

The structure of ectomycorrhizae synthesized between the E-strain fungus, Wilcoxina mikolae var. mikolae and two tree species, Picea mariana and Betula alleghaniensis, was characterized by light microscopy and scanning electron microscopy. For both mycorrhizal types, mantle formation was visible on lateral roots within 10 days of inoculation. Picea mariana ectomycorrhizae had a very thin mantle whereas B. alleghaniensis ectomycorrhizae had a mantle consisting of several layers. For both mycorrhizal types, the innermost mantle hyphae were embedded in a considerable amount of mucigel on the root surface. A well-developed Hartig net with labyrinthic growth occurred in both types of mycorrhizae. Betula alleghaniensis ectomycorrhizae had a paraepidermal Hartig net, and the root epidermal cells were radially elongate at an oblique angle. The Hartig net of P. mariana ectomycorrhizae penetrated the epidermis and all layers of the cortex. The cytoplasmic density of the intercellular hyphae was greatest towards the root apex. Ectomycorrhizal associations formed by E-strain fungi were similar to ectomycorrhizae formed by other fungi. Key words: E-strain, ectomycorrhizae, Wilcoxina, Picea, Betula, Hartig net.

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