Showing papers on "Root hair published in 1977"

Effects of Mechanical Impedance on Root Growth in Barley, Hordeum vulgare L.

Abstract: The effects of mechanical stress on whole root systems was investigated using beds of solid glass spheres (ballotini) continuously supplied with aerated nutrient solution. As noted in earlier experiments, increased mechanical impedance slowed root extension and altered cell size and number; it also caused distortion of the root apex, stimulated growth of lateral shoot meristems, and induced the formation of nodal roots. The development of lateral branch roots was enhanced and where root axes curved around ballotini lateral roots formed preferentially on the outer (convex) side whereas root hairs developed on the inner (concave) side. After roots were relieved from mechanical stress at least 3 d elapsed before the rate of extension growth equalled that of unimpeded plants. When intact Zea mays root apices first made contact with ballotini their elongation was slowed by 70% for about 10 min; where root caps were removed before the roots made contact, no such effects were seen. We discuss the general nature of the mechanism of response to mechanical stress.

Comparative root morphology of some pasture grasses and clovers

Abstract: Root systems of three clovers and five pasture grasses grown in sand culture during summer and in soil during winter were examined at two stages of growth.There were large differences in shoot/root ratio between harvests, but no consistent differences among species. In general grasses had longer, thinner, more finely branched roots than clovers, but had similar root surface areas per unit dry weight; grasses also had longer, more frequent root hairs. Of the grasses, Lolium perenne was the most similar to the clovers and Cynosurus cristatus the least similar. Because root hairs of grasses were longer and more frequent, the calculated surface of the root hair cylinder and the volume within the root hair cylinder were several times greater than those of clovers. These differences could give the grasses a strong competitive advantage over the clovers in nutrient and water uptake, especially of immobile nutrients such as phosphate.

Receptor site on clover and alfalfa roots for Rhizobium.

Abstract: Sites on white clover and alfalfa roots that bind Rhizobium trifolii and R. meliloti capsular polysaccharides, respectively, were examined by fluorescence microscopy. Fluorescein isothiocyanate-labeled capsular material from R. trifolii bound specifically to root hairs of clover but not alfalfa. Binding was most intense at the root hair tips. Treatment of clover roots with 2-deoxyglucose (2-dG) prevented binding of R. trifolii capsular material to the roots. The sugar 2-dG enhanced the elution of clover root protein, which could bind to and specifically agglutinate R. trifolii but not R. meliloti or R. japonicum. The mild elution procedure left the roots intact. Agglutination of R. trifolii and passive hemagglutination of rabbit erythrocytes coated with the capsular material of R. trifolii were specifically inhibited by 2-dG. These results suggest that clover roots contain proteins that cross-link complementary polysaccharides on the surface of clover root hairs and infective R. trifolii through 2-dG-sensitive binding sites. Alfalfa root hairs were shown to specifically bind to a surface polysaccharide from R. meliloti.

Rhizobium-stimulated Callose Formation in Clover Root Hairs and its Relation to Infection

Abstract: Callose was detected in the cell walls of the tips of growing root hairs of Trifolium species and the non-legume Phleum pratense using u.v. fluorescence of fresh material stained with 0-005% aniline blue. Inoculation of the roots with Rhizobium trifolii, R. legnminosarum, R. meliloti, and R. japonicum, or addition of 10-7 and 10~8 M indole-3-acetic acid (IAA) increased tip callose formation. Most tip callose was formed at 12 °C, and amounts declined progressively at 18, 24, and 30 °C, with very little formed at 36 °C. Tip callose usually became less and disappeared in individual root hairs as they aged. Callose which appeared prominently in the host cell walls at the points of initiation of infection threads did not usually disappear as the hairs matured. There was little or no extension of callose along the infection thread and none in the thread tip or in the cell nucleus. Presumptive regions of callose had similar structure and electron density as root hair wall material and were sometimes related to arrays of vesicles in the host cytoplasm. The external surface of the hair wall bore small pegs or papillae (0-1-0-2 p.m) continuous with the outer layer of the wall and possibly associated with attachment of bacteria. Bacteria were usually umbonate at the point of attachment and their polyphosphate granules were much larger near the root hair than at the distal end.

Ultrastructural and immunological demonstration of the nodulation of the European Alnus glutinosa (L.) Gaertn. host plant by the North-American Alnus crispa var. mollis Fern, root nodule endophyte

Abstract: The inoculation of the European Alnus glutinosa (L.) Gaertn. host plant by a crushed-nodule inoculum, prepared with the North-American Alnus crispa var. mollis Fern, root nodule, was successful. Fluorescein- and ferritin-labelled antibodies, specific against the A. crispa var. mollis root nodule endophyte (Lalonde et al. 1975), demonstrated the identity of this endophyte in the resulting nodules. The nodulation process of this abnormal host–endophyte system was studied by light and electron microscopy. An excretion of host blebs containing electron-dense polysaccharide material, resulting in the formation of exo-encapsulation threads containing presumptive endophytic bacterial cells, was associated with deformed root hairs. Originating from an exoen-capsulation thread, the endophyte penetrates the root hair cell and then migrates as a hypha toward the cortical cells of the root. Its migration in the cortical cells of the primary nodule results in the induction of a lateral root which develops as the true ...

In vitro growth of mouse hair root.

Abstract: Hair roots from mouse dorsal skin continued to grow in culture medium for 10 h or more after isolation Under observation by time-lapse cinematography, the cultured hair roots appeared to grow downward We observed both the downward growth of the cultured hair roots as well as the transfer of melanosomes from melanocytes to cortical cells The hair roots were also capable of incorporating the labelled amino acid and thymidine

Differential enzyme activity during trichoblast differentiation in elodea canadensis

Abstract: A B S T R A C T Enzymes active in the developing root epidermis of Elodea caniadentsis Michx. were demonstrated by histochemical techniques. The future root-hair-forming cells (trichoblasts) showed a period of elevated activity more extensive than the one previously reported in trichoblasts of another species for dehydrogenases (glucose-6-phosphate, pyruvate, lactate, succinic, isocitrate. glutamate), phosphatases (acid, ATPase, 5-nucleotidase), cytochrome oxidase, and peroxidase. This elevated activity extended from the time of trichoblast formation up to the point of root hair outgrowth, even for enzymes not previously demonstrated in trichoblasts: alkaline phosphatase, NADH diaphorase, NADPH diaphorase, esterase, and leucine aminopeptidase. Glucose-6-phosphatase and aryl sulfatase were not detected. The single exception to this pattern was phosphorylase activity, which intensified only just prior to and during root hair outgrowth. The more generalized activity pattern is considered to indicate the so-called meristematic character of these cells in terms of both macromolecular synthesis and lack of specialization. It is suggested that specific root hair development begins just prior to initiation, at the point marked by elevated phosphorylase activity. THE ROOT HAIR and nonpiliferous cells in the epidermis of Elodea canadensis Michx. develop from daughter cells of differing size, resulting from an asymmetric division. Several developmental steps have been observed to occur only in the shorter trichoblasts (Biinning, 1957; Cutter and Feldman, 1970a, b) and are thus believed to be important for their differentiation as root hairs. Among these is the strong increase in enzyme activity reported in Phleum pratense (Avers, 1958, et seq.).

Root Hair Cell Enhancement in Tissue Cultures from Soybean Roots: A Useful Model System In Vitro Rhizobium Symbiosis

Abstract: A technique for obtaining large numbers of root hair cells in cell cultures from soybeans is described. The cells were grown on agar containing the Prairie Regional Laboratory B5 (PRL-B5) medium for periods longer than 60 days. Mixed populations of cultured root hair cells and cortical cells were used to study the in vitro association between soybean cells and Rhizobium japonicum. The advantages of these types of root cell cultures in studies of symbiosis are discussed.

Preliminary studies on the development and structure of root nodules inCasuarina equisetifolia L.

Abstract: The structure and development of the root nodule ofCasuarina equisetifolia have been studied.

Formation of Root Hair in Crown Roots of Rice Plants and Nitrogen Fertilizer

Abstract: It had been ascertained by the authors that nitrogen fertilizer accelerates root hair formation and growth in the lateral roots of rice plants. But the effects of nitrogen fertilizer on root hairs of crown roots have not been ascertained. The present investigation was carried out to study the morphogenetical effects of nitrogen fertilizer on the development of root hairs in crown roots, and the effect on the physiological longevity of the root hairs by means of ribonucleic acid (RNA) detection. The following results were obtained: Generally, the root hairs which developed on the thicker crown roots were more numerous per unit crown root length and longer in length than those of the thinner crown roots (Figs. 1, 2, 3 and 4). As regards the morpho-genetical effects of nitrogen fertilizer on the development of root hairs, it was found that root hair formation and growth in crown roots were accelerated when a high level of nitrogen fertilizer was given to the rice plants (Tables 3 and 5). It was also found that the percentage of root hairs containing RNA increased in proportion to the nitrogcn fertilizer amount given to the rice plants (Fig. 6). From these results it may be assumed that nitrogen fertilizer affects root hair formation and growth, and it also affects maturation of root hairs in crown roots.