Chemotaxis of zoospores of Phytophthora megasperma to primary roots of alfalfa seedlings

1978 ◽  
Vol 56 (7) ◽  
pp. 795-800 ◽  
Author(s):  
C. C. Chi ◽  
F. E. Sabo
Keyword(s):  
Trifolium Pratense ◽  
Primary Root ◽  
Root Hairs ◽  
Red Clover ◽  
Root Surface ◽  
Root Cap ◽  
Root Tips ◽  
Phytophthora Megasperma ◽  
Root Area ◽  
Primary Roots

Chemotaxis of the zoospores of Phytophthora megasperma was studied on freshly excised primary root tips of 2-day-old seedlings of nine alfalfa (Medicago sativa L.) cultivars and four other legume species. The highly susceptible cultivars Saranac, Algonquin, and Vernal attracted masses of zoospores within minutes after being placed into fresh zoospore suspensions. The moderately susceptible cultivars Iroquois, Angus, and Thor displayed less severe en masse zoospore accumulation. Resistant cultivars Apollo, Agate, and to a lesser degree WL-318 exhibited minor chemotaxis.Zoospores were strongly attracted to the region of elongation, immediately above the root cap area. Relatively few zoospores, if any, were attracted to the root cap and older regions of the roots. Zoospores were not attracted to root hairs. Within 0.5-1 h, zoospores attracted to the roots began to encyst and germinate. Germ tubes always originated from the side of cysts closest to the root surface, and all showed unidirectional growth towards the root.Very weak or no chemotactic responses of zoospores to nonhost legume plants of white sweet clover (Melilotus alba Desr.), red clover (Trifolium pratense L.), bird's-foot trefoil (Lotus corniculatus L.), and soybean (Glycine max (L.) Merr. cv. Vansoy) were observed. Roots of susceptible alfalfa seedlings pretreated in boiling water did not attract zoospores.Injured, susceptible alfalfa roots displayed a strong preferential attraction around a wounded root area. Varying zoospore densities occurred at different distances from the wound. Wounded, resistant alfalfa roots showed slightly more zoospore accumulation than the uninjured resistant roots.The magnitude of chemotaxis and response time appear to be related to the susceptibility or resistance of the young, primary roots of alfalfa seedlings.

Cytological and histochemical characteristics of the axenic root surface of Alnus glutinosa

1986 ◽  
Vol 64 (10) ◽  
pp. 2216-2226 ◽  
Author(s):  
Yves Prin ◽  
Mireille Rougier
Keyword(s):  
Cell Wall ◽  
Root Hair ◽  
Root Hairs ◽  
Root Apex ◽  
Alnus Glutinosa ◽  
Root Surface ◽  
Infection Process ◽  
Root Cap ◽  
A Cell ◽  
Histochemical Tests

The aim of the present study was to investigate the Alnus root surface using seedlings grown axenically. This study has focused on root zones where infection by the symbiotic actinomycete Frankia takes place. The zones examined extend from the root cap to the emerging root hair zone. The root cap ensheaths the Alnus root apex and extends over the root surface as a layer of highly flattened cells closely appressed to the root epidermal cell wall. These cells contain phenolic compounds as demonstrated by various histochemical tests. They are externally bordered by a thin cell wall coated by a thin mucilage layer. The root cap is ruptured when underlying epidermal cells elongate, and cell remnants are still found in the emerging root hair zone. Young emerging root hairs are bordered externally by a cell wall covered by a thin mucilage layer which reacts positively to the tests used for the detection of polysaccharides, glycoproteins, and anionic sites. The characteristics of the Alnus root surface and the biological function of mucilage and phenols present at the root surface are discussed in relation to the infection process.

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 RNA-Seq Transcriptome Analysis of Rice Primary Roots Reveals the Role of Flavonoids in Regulating the Rice Primary Root Growth

Genes ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 213
Author(s):  
Yu Xu ◽  
Junjie Zou ◽  
Hongyan Zheng ◽  
Miaoyun Xu ◽  
Xuefeng Zong ◽  
...  
Keyword(s):  
Cell Wall ◽  
Root Growth ◽  
Primary Root ◽  
Glutathione Metabolism ◽  
Auxin Signaling ◽  
Antioxidant Enzyme Activities ◽  
Rna Seq ◽  
Root Tips ◽  
Primary Roots ◽  
Quercetin Treatment

Flavonoids play important roles in root development and in its tropic responses, whereas the flavonoids-mediated changes of the global transcription levels during root growth remain unclear. Here, the global transcription changes in quercetin-treated rice primary roots were analyzed. Quercetin treatment significantly induced the inhibition of root growth and the reduction of H2O2 and O2− levels. In addition, the RNA-seq analysis revealed that there are 1243 differentially expressed genes (DEGs) identified in quercetin-treated roots, including 1032 up-regulated and 211 down-regulated genes. A gene ontology (GO) enrichment analysis showed that the enriched GO terms are mainly associated with the cell wall organization, response to oxidative stress, and response to hormone stimulus. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment pathway analysis showed that the enriched DEGs are involved in phenylpropanoid biosynthesis, glutathione metabolism, and plant hormone signal transduction. Moreover, the quercetin treatment led to an increase of the antioxidant enzyme activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) in rice roots. Also, the quercetin treatment altered the DR5:GUS expression pattern in the root tips. All of these data indicated that the flavonoids-mediated transcription changes of genes are related to the genes involved in cell wall remodeling, redox homeostasis, and auxin signaling, leading to a reduced cell division in the meristem zone and cell elongation in the elongation zone of roots.

Phosphorus acquisition from compacted soil by hyphae of a mycorrhizal fungus associated with red clover (Trifolium pratense)

1997 ◽  
Vol 75 (5) ◽  
pp. 723-729 ◽  
Author(s):  
Xiao-Lin Li ◽  
Jun-Ling Zhang ◽  
Eckhard George ◽  
Horst Marschner
Keyword(s):  
Bulk Density ◽  
Soil Compaction ◽  
Trifolium Pratense ◽  
Mycorrhizal Fungus ◽  
Red Clover ◽  
Arbuscular Mycorrhizal ◽  
Soil Bulk Density ◽  
Root Surface ◽  
P Uptake ◽  
Compacted Soil

The influence of an arbuscular mycorrhizal fungus, Glomus mosseae, on the adverse effects of soil compaction on growth and phosphorus (P) uptake of red clover was studied in a model experiment. The pots used in the experiment had three compartments, a central one with a soil bulk density of 1.3 g ∙ cm−3 and two outer compartments with three different levels of soil bulk density (1.3, 1.6, or 1.8 g ∙ cm−3). The soil in the outer compartments was fertilized with P and was either freely accessible to roots and hyphae, or separated by nets and accessible to hyphae only. At a soil bulk density of 1.3 g ∙ cm−3, mycorrhizal plants did not absorb more P than nonmycorrhizal plants except when access of roots to the outer compartments was restricted by nets. At high soil bulk density, root growth was drastically decreased. However, hyphae of G. mosseae absorbed P even from highly compacted soil, and induced a P-depletion zone of about 30 mm from the root surface. In consequence, at higher soil bulk density shoot P concentration and the total amount of P in the shoot were higher in mycorrhizal than in nonmycorrhizal plants. This experiment showed that hyphae of G. mosseae are more efficient in obtaining P from compacted soil than mycorrhizal or nonmycorrhizal roots of red clover. Key words: arbuscular mycorrhiza, phosphorus, red clover (Trifolium pratense L.), soil bulk density, soil compaction.

Graviresponsiveness and cap dimensions of primary and secondary roots of Ricinus communis (Euphorbiaceae)

1984 ◽  
Vol 62 (8) ◽  
pp. 1767-1769 ◽  
Author(s):  
Randy Moore ◽  
John Pasieniuk
Keyword(s):  
Castor Bean ◽  
Ricinus Communis ◽  
Primary Root ◽  
Root Cap ◽  
Primary Roots ◽  
Secondary Roots

After branching from the primary root, secondary roots of castor bean (Ricinus communis) grow laterally for 15–20 mm, after which they bend downward (i.e., become positively gravitropic). During the first 10 mm of growth, the lengths of caps of secondary roots increase from 120 ± 26 to 220 ± 28 μm. Although this increase is statistically significant (P < 0.1%), the resulting secondary roots are only minimally graviresponsive. A subsequent doubling of the lengths and widths of the root caps (i.e., to 420 ± 34 and 450 ± 41 μm, respectively) is positively correlated with the onset of gravicurvature. The graviresponsiveness and dimensions of caps of positively gravitropic secondary roots are not significantly different from those of positively gravitropic primary roots. These results indicate that (i) a statistically significant increase in the length and length:width ratio of a root cap does not necessarily result in the root becoming positively gravitropic, (ii) there may be a minimum cap length and (or) width necessary for graviresponsiveness, and (iii) the degree of graviresponsiveness exhibited by a particular root may be related to the size of its root cap.

scholarly journals Evaluation of Metaxylem Vessel Histogenesis and the Occurrence of Vessel Collapse during Early Development in Primary Roots of Zea mays ssp. mexicana: A Result of Premature Programmed Cell Death?

Plants ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 374
Author(s):  
Susumu Saito ◽  
Teruo Niki ◽  
Daniel K. Gladish
Keyword(s):  
Cell Death ◽  
Zea Mays ◽  
Programmed Cell Death ◽  
Primary Root ◽  
Cell Types ◽  
Root Apical Meristem ◽  
Root Tips ◽  
Primary Roots ◽  
Transmission Electron ◽  
Vessel Elements

Root apical meristem histological organization in Zea mays has been carefully studied previously. Classical histology describes its system as having a “closed organization” and a development of xylem that conforms to predictable rules. Among the first cell types to begin differentiation are late-maturing metaxylem (LMX) vessels. As part of a larger study comparing domestic maize root development to a wild subspecies of Z. mays (teosinte), we encountered a metaxylem development abnormality in a small percentage of our specimens that begged further study, as it interrupted normal maturation of LMX. Primary root tips of young seedlings of Zea mays ssp. mexicana were fixed, embedded in appropriate resins, and sectioned for light and transmission electron microscopy. Longitudinal and serial transverse sections were analyzed using computer imaging to determine the position and timing of key xylem developmental events. We observed a severe abnormality of LMX development among 3.5% of the 227 mexicana seedlings we screened. All LMX vessel elements in these abnormal roots collapsed and probably became non-functional shortly after differentiation began. Cytoplasm and nucleoplasm in the abnormal LMX elements became condensed and subdivided into irregularly-shaped “macrovesicles” as their cell walls collapsed inward. We propose that these seedlings possibly suffered from a mutation that affected the timing of the programmed cell death (PCD) that is required to produce functional xylem vessels, such that autolysis of the cytoplasm was prematurely executed, i.e., prior to the development and lignification of secondary walls.

scholarly journals The cap size and shape of Arabidopsis thaliana primary roots impact the root responses to an increase in medium strength

2018 ◽  
Author(s):  
J. Roué ◽  
H. Chauvet ◽  
N. Brunel-Michac ◽  
F. Bizet ◽  
B. Moulia ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Primary Root ◽  
Root Cap ◽  
Size And Shape ◽  
Primary Roots ◽  
Medium Strength ◽  
Cell Layers ◽  
Root Responses ◽  
Mutant Lines

AbstractDuring root progression in soil, root cap cells are the first to encounter obstacles. The root cap is known to sense environmental cues, making it a relevant candidate for a mechanosensing site. An original two-layer medium was developed in order to study root responses to growth medium strength and the importance of the root cap in the establishment of these responses. Root growth and trajectory of primary roots of Arabidopsis thaliana seedlings were investigated using in vivo image analysis. After contact with the harder layer, the root either penetrated it or underwent rapid curvature, enabling reorientation of the root primary growth. The role of the root cap in tip reorientation was investigated by analyzing the responses of Arabidopsis mutant roots with altered caps. The primary root of fez-2 mutant lines, which has fewer root cap cell layers than wild-type roots, showed impaired penetration ability. Conversely, smb-3 roots of mutant lines, which display a higher number of root cap cells, showed enhanced penetration abilities. This work highlights that alterations in root cap shape and size affect the root responses to medium strength.HighlightThe analysis of the growth and orientation of Arabidopsis thaliana mutant roots affected in root cap size and shape showed that properly formed root cap is required to trigger the root responses to medium strength.AbbreviationsCOLcolumella;LRCLateral Root Cap;SISharpness Index;SMBSOMBRERO.

scholarly journals Tomato roots sense horizontal/vertical mechanical impedance and divergently modulate root/shoot metabolome

2021 ◽  
Author(s):  
Alka Kumari ◽  
Sapana Nongmaithem ◽  
Sameera Devulapalli ◽  
Yellamaraju Sreelakshmi ◽  
Rameshwar Sharma
Keyword(s):  
Lateral Roots ◽  
Primary Root ◽  
Mechanical Impedance ◽  
Common Denominator ◽  
Root Tips ◽  
Vertical Orientation ◽  
Tomato Seedlings ◽  
Primary Roots ◽  
Tomato Roots ◽  
Metabolite Profiles

AbstractPlant roots encounter coarse environs right after emergence from the seeds. Little is known about metabolic changes enabling roots to overcome the soil impedance. Tomato seedlings grown vertically or horizontally, at increasing hardness, exhibited lateral roots proliferation, shorter hypocotyls, and primary roots. In primary root tips, hardness-elicited loss of amyloplasts staining; induced ROS and NO accumulation. The levels of IBA, zeatin, jasmonates, and salicylic acids markedly differed in roots and shoots exposed to increasing hardness. Hardness lowered IAA and elevated ABA levels, while increased ethylene emission was confined to horizontally-impeded seedlings. The trajectories of metabolomic shifts distinctly differed between vertically/horizontally-impeded roots/shoots. In horizontal roots, amino acids were the major affected group, while in vertical roots, sugars were the major group. Commonly affected metabolites in roots and shoots, trehalose, dopamine, caffeoylquinic acid, and suberic acid, hallmarked the signature for hardness. Increasing hardness lowered SnRK1a expression in roots/shoots implying regulation of metabolic homeostasis by the SnRK1 signalling module. Our data suggest that though hardness is a common denominator, roots sense the horizontal/vertical orientation and correspondingly modulate metabolite profiles.Significance statementWe show that the tomato roots sense the magnitude of hardness as well as the horizontal and vertical orientation. The hardness divergently modulates the phytohormone and metabolite levels in roots and shoots. The trajectory of the metabolic shift in vertically-grown seedling distinctly differs from horizontally-grown seedlings. ABA and trehalose were the hallmark of hardness stress and may influence metabolic alteration via the SNRK signalling pathway.

scholarly journals Role of Ascorbate in the Regulation of the Arabidopsis thaliana Root Growth by Phosphate Availability

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Jarosław Tyburski ◽  
Kamila Dunajska-Ordak ◽  
Monika Skorupa ◽  
Andrzej Tretyn
Keyword(s):  
Root Growth ◽  
Lateral Root ◽  
Root Elongation ◽  
Lateral Roots ◽  
Primary Root ◽  
Root Hairs ◽  
P Availability ◽  
Root Tips ◽  
P Deficiency ◽  
Phosphate Availability

Arabidopsis root system responds to phosphorus (P) deficiency by decreasing primary root elongation and developing abundant lateral roots. Feeding plants with ascorbic acid (ASC) stimulated primary root elongation in seedlings grown under limiting P concentration. However, at high P, ASC inhibited root growth. Seedlings of ascorbate-deficient mutant (vtc1) formed short roots irrespective of P availability. P-starved plants accumulated less ascorbate in primary root tips than those grown under high P. ASC-treatment stimulated cell divisions in root tips of seedlings grown at low P. At high P concentrations ASC decreased the number of mitotic cells in the root tips. The lateral root density in seedlings grown under P deficiency was decreased by ASC treatments. At high P, this parameter was not affected by ASC-supplementation. vtc1 mutant exhibited increased lateral root formation on either, P-deficient or P-sufficient medium. Irrespective of P availability, high ASC concentrations reduced density and growth of root hairs. These results suggest that ascorbate may participate in the regulation of primary root elongation at different phosphate availability via its effect on mitotic activity in the root tips.

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