Callose-Deposit Formation in Radish Root Hairs

A micropotometric device previously described by the writer was used to determine quantitatively the velocity of water influx in cubic microns per square micron of hair surface per minute of comparatively older and younger root hairs of radish seedlings in a humid atmosphere at 29° ± 1°C. when the micropotometers were filled with Hoagland solution at pH 6.8. In each experiment, measurements were made on two hairs of different length and different age on a given root and the hairs were inserted into the micropotometers a sufficient distance so that the area of immersion, 13,200µ2, was the same in each instance. The range of velocities of water influx through the immersed surface was 4.46 to 1.16µ3/µ2/min. for the younger and shorter hairs which varied in length from 280 to 460 microns. The range of velocities of water influx through the immersed surface of the older hairs which varied from 661 to 2300 microns in length was 1.94 to 0.47µ3/µ2/min. The data indicate that water entry slows down in older hairs independent of root length. Estimations were made of the times to replace hair volumes based upon the mean velocities of water entry of the immersed areas. It was found that the time for the hairs to absorb an amount of water equivalent to their own volumes under the conditions specified was a matter of minutes or less; the range was 0.90 to 8.51 minutes.

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Microtubules are at the tips of root hairs and form helical patterns corresponding to inner wall fibrils

Journal of Cell Science ◽

10.1242/jcs.75.1.225 ◽

1985 ◽

Vol 75 (1) ◽

pp. 225-238 ◽

Cited By ~ 1

Author(s):

C.W. Lloyd ◽

B. Wells

Keyword(s):

Cell Wall ◽

Phosphate Buffer ◽

Tip Growth ◽

Root Hairs ◽

Onion Root ◽

Apical Dome ◽

Radish Root ◽

Contradictory Evidence ◽

Shadow Cast ◽

Optimized Conditions

Root hairs have sometimes provided contradictory evidence for microtubule/microfibril parallelism. This tissue was re-examined using optimized conditions for the fixation, before immunofluorescence, of root hairs. In phosphate buffer, microtubules did not enter the apical tip of radish root hairs and were clearly fragmented. However, in an osmotically adjusted microtubule-stabilizing buffer, microtubules were observed within the apical dome and appeared unfragmented. Microtubules are not, therefore, absent from the region where new cell wall is presumed to be generated during tip growth. A spiralling of microtubules was seen at the apices of onion root hairs. Using shadow-cast preparations of macerated radish root hairs, it was confirmed that steeply helical microtubules matched the texture of the inner wall. In onion, the 45 degrees microtubular helices are accompanied by similarly wound inner wall fibrils. Results do not support the view that microtubules are not involved in the oriented deposition of fibrils in root hairs. Instead, they are interpreted in terms of a flexible helical cytoskeleton, which is capable of changing its pitch but is sensitive to fixation conditions.

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Arrangement of microtubules and microfilaments during oriented secondary wall formation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100082170 ◽

1978 ◽

Vol 36 (2) ◽

pp. 262-263

Author(s):

R. W. Seagull

Keyword(s):

Root Hair ◽

Secondary Wall ◽

Tip Growth ◽

Higher Plants ◽

Root Hairs ◽

Cortical Microtubules ◽

Radish Root ◽

Secondary Wall Formation ◽

Cellular Components ◽

Being Moved

Introduction. Microtubules have long been hypothesized to function as track-like elements, directing cellular components (Hepler & Palevitz 1974). In higher plants, cortical microtubules (cmt) have been hypothesized to function in this manner in the orientation of secondary wall microfibrils (MF) (reviewed by Heath, 1974). Involvement in such a process requires that the cmt be close to the structures being moved, be parallel to the direction of orientation and be of sufficient length to function as guide elements. In radish root hairs, sub-pl cmt occur along the length of the hair, paralleling the secondary wall MF. Root hair elongation occurs via tip growth, which results in simultaneous deposition of primary, randomly arranged MF (first 25 μm of root hair) and secondary, oriented MF (distances greater than 25 μm, Fig. 1).Results. Longitudinal serial sections show that cmt start and terminate randomly throughout the length of the hair, but are absent in the tip region (0-3 μm from tip). Microtubules are rarely found more than 500 nm from the pl. Bridges between cmts and the pl are evident, Fig. 4. In the region between 20 and 60 μm from the tip, 50% of the cmt are less than 1 μm long.

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Use of SEM, X-ray analysis and TEM to localize Fe3+ reduction in roots

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100104029 ◽

1988 ◽

Vol 46 ◽

pp. 392-393 ◽

Cited By ~ 3

Author(s):

William P. Wergin ◽

P. F. Bell ◽

Rufus L. Chaney

Keyword(s):

Electron Microscopy ◽

Root Hairs ◽

Rapid Reduction ◽

X Ray ◽

Physical Evidence ◽

Transmission Electron ◽

Young Root ◽

Insoluble Precipitate ◽

Uptake And Transport ◽

Scanning Electron

In dicotyledons, Fe3+ must be reduced to Fe2+ before uptake and transport of this essential macronutrient can occur. Ambler et al demonstrated that reduction along the root could be observed by the formation of a stain, Prussian blue (PB), Fe4 [Fe(CN)6]3 n H2O (where n = 14-16). This stain, which is an insoluble precipitate, forms at the reduction site when the nutrient solution contains Fe3+ and ferricyanide. In 1972, Chaney et al proposed a model which suggested that the Fe3+ reduction site occurred outside the cell membrane; however, no physical evidence to support the model was presented at that time. A more recent study using the PB stain indicates that rapid reduction of Fe3+ occurs in a region of the root containing young root hairs. Furthermore the most pronounced activity occurs in plants that are deficient in Fe. To more precisely localize the site of Fe3+ reduction, scanning electron microscopy (SEM), x-ray analysis, and transmission electron microscopy (TEM) were utilized to examine the distribution of the PB precipitate that was induced to form in roots.

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Techniques for preparing the Lolium perenne coleorhiza for scanning electron microscope evaluation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100124239 ◽

1992 ◽

Vol 50 (1) ◽

pp. 766-767

Author(s):

Susan B.G. Debaene ◽

John S. Gardner ◽

Phil S. Allen

Keyword(s):

Electron Microscope ◽

Scanning Electron Microscope ◽

Lolium Perenne ◽

Morphological Study ◽

Root Hairs ◽

Inner Pressure ◽

Water Potentials ◽

Radicle Emergence ◽

Standard Fixation ◽

Scanning Electron

The coleorhiza is a nonvascular sheath that encloses the embryonic radicle in Poaceae, and is generally the first tissue to emerge during germination. Delicate hairlike extensions develop from some coleorhiza cells prior to radicle emergence. Similar to root hairs, coleorhiza hairs are extremely sensitive to desiccation and are damaged by exposure to negative water potentials. The coleorhiza of Lolium perenne is somewhat spherical when first visible, after which a knob forms at a right angle to the caryopsis due to inner pressure from the elongating radicle. This knob increases in length until the radicle finally punctures the coleorhiza. Standard fixation procedures cause severe desiccation of coleorhiza cells and hairs, making morphological study of the coleorhiza difficult. This study was conducted to determine a more successful process for coleorhiza preservation.

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SEM and fluorescence imaging of callose deposition in root hair tips and suspension cultures of Streptanthus tortuosus

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100161047 ◽

1990 ◽

Vol 48 (3) ◽

pp. 698-699

Author(s):

K.S. Walters ◽

R.D. Sjolund ◽

K.C. Moore

Keyword(s):

Cell Wall ◽

Root Hair ◽

Cultured Cells ◽

Root Hairs ◽

Callus Cultures ◽

Callose Deposition ◽

Culture Cells ◽

Wall Structures ◽

Ultraviolet Illumination ◽

Callose Formation

Callose, B-1,3-glucan, a component of cell walls, is associated with phloem sieve plates, plasmodesmata, and other cell wall structures that are formed in response to wounding or infection. Callose reacts with aniline blue to form a fluorescent complex that can be recognized in the light microscope with ultraviolet illumination. We have identified callose in cell wall protuberances that are formed spontaneously in suspension-cultured cells of S. tortuosus and in the tips of root hairs formed in sterile callus cultures of S. tortuosus. Callose deposits in root hairs are restricted to root hair tips which appear to be damaged or deformed, while normal root hair tips lack callose deposits. The callose deposits found in suspension culture cells are restricted to regions where unusual outgrowths or protuberances are formed on the cell surfaces, specifically regions that are the sites of new cell wall formation.Callose formation has been shown to be regulated by intracellular calcium levels.

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