Primary vascular patterns in root meristems of Pontederia cordata and their relevance to studies of root development

1980 ◽  
Vol 58 (12) ◽  
pp. 1351-1369 ◽  
Author(s):  
W. A. Charlton
Keyword(s):  
Apical Meristem ◽  
Vascular System ◽  
Root Apex ◽  
Root Apical Meristem ◽  
Vascular Pattern ◽  
Quiescent Centre ◽  
Vascular Differentiation ◽  
Pontederia Cordata ◽  
Distribution Of Components ◽  
Root Apices

There are several files of metaxylem cells in root apices of Pontederia cordata L., each considered to consist of a series of prospective vessels with their ends in contact. Two longitudinally adjacent vessels may be in the same file of cells produced by the root apex or in adjacent files. As the root grows, successive prospective vessels are added to the apical ends of most of the files but not all files are continued. Addition of prospective vessels appears to take place within the "quiescent centre" of the root apical meristem. Where files are not continued there is no immediate readjustment of remaining files. The longitudinal and transverse distribution of components of the vascular system (including protophloem and protoxylem) is discussed in relation to the means by which the pattern of development may be controlled. Rates of production of vessels and the final lengths of the vessels are estimated. The observations and deductions are discussed in relation to other studies of root growth, vascular differentiation, and vascular pattern formation and maintenance.

scholarly journals The quiescent centre and root apical meristem: organization and function

2021 ◽  
Author(s):  
Joseph G Dubrovsky ◽  
Kris Vissenberg
Keyword(s):  
Root Growth ◽  
Apical Meristem ◽  
100Th Anniversary ◽  
Root Apical Meristem ◽  
Quiescent Centre ◽  
Special Issue ◽  
Future Directions ◽  
Cell Production ◽  
And Function

Abstract This special issue is dedicated to the 100th anniversary of the birth of Frederick Albert Lionel Clowes, who discovered the quiescent centre (QC) of the root apical meristem (RAM). His discovery was a foundation for contemporary studies of the QC and RAM function, maintenance, and organization. RAM function is fundamental for cell production and root growth. This special issue bundles reviews on the main tendencies, hypotheses, and future directions, and identifies unknowns in the field.

scholarly journals Activation of embryo during rape (Brassica napus L.) seed germination II. Transversal organisation of radicle apical meristem

2014 ◽  
Vol 49 (4) ◽  
pp. 387-395 ◽  
Author(s):  
Mieczysław Kuraś
Keyword(s):  
Brassica Napus ◽  
Seed Germination ◽  
Cross Sections ◽  
Apical Meristem ◽  
Mature Embryo ◽  
Root Cap ◽  
Root Apical Meristem ◽  
Quiescent Centre ◽  
Brassica Napus L ◽  
Cell Patterns

Series of microtome cross sections of the root apical meristem were investigated in the mature embryo and young seedling of rape. The cell patterns are described in 3 layers of promeristem. Radial sectors of the root cap and protoderm, formed by common dermatocalyptrogen initials, and radial sectors of the cortex, produced by periblem initials were identified on all cross sections of the root. Between these sectors 4 segmentation boundaries of proembryo quadrants were distinguished, running across the whole root proper. The boundaries between the 4 sectors of connecting cells arising from the upper hypophysis derivative and the boundaries between the 4 sectors of the columella originating from the lower hypophysis derivative do not follow the same course and are not identical with the boundaries of the proembryo quadrants. Therefore during the whole embryogenesis, the central connecting cells, considered generally as cortex initials (iec), take no part in the development of the cortex but they form the quiescent centre of the radicle. Neither do the columella initial cells participate in the development of the lateral parts of the root cap.

The indirect effect of exogenous auxin on initiation of cell divisions in wheat root expiants (Triticum aestivum) during callus induction

1989 ◽  
Vol 67 (7) ◽  
pp. 1979-1984
Author(s):  
Dalia T. Kudirka ◽  
Blanche B. Brightwell
Keyword(s):  
Triticum Aestivum ◽  
Mitotic Activity ◽  
Apical Meristem ◽  
Primary Root ◽  
Root Apex ◽  
Wheat Root ◽  
Root Apical Meristem ◽  
Root Explants ◽  
Cell Divisions ◽  
Synthetic Auxins

Mitotic activity (indices) was measured in apical and nonapical regions of primary root explants excised from 2-day-old germinating seedlings of wheat (Triticum aestivum Thell em L.) and cultured in the presence of the synthetic auxins 3,6-dichloro-O-anisic acid (dicamba) and 2,4-dichlorophenoxyacetic acid (2,4-D). Mitotic activity in the root apical meristem decreased with increasing concentration of auxin in the culture media. Correlated with the decrease of mitotic activity in the root apical meristem was an increase of mitotic activity in nonapical regions of the root. The degree of cell division activity initiated in nonapical regions of the root was (i) inversely proportional to the degree of inhibition of cell divisions in the root apex, but (ii) independent of the concentration of auxin in the culture medium. These data suggest that the primary effect of these synthetic auxins on mitotic activity in wheat root explants is to suppress cell divisions in the primary root apex and not to stimulate cell divisions in the nonapical regions of the root. Cell cycle control in nonapical regions of the root appears to be a function of factor(s) emanating from mitotically active cells of the primary apical meristem.

The quiescent centre of the root apical meristem: Conceptual developments from Clowes to modern times

2021 ◽  
Author(s):  
Joseph G Dubrovsky ◽  
Victor B Ivanov
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Stem Cell Niche ◽  
Apical Meristem ◽  
Root Apical Meristem ◽  
Quiescent Centre ◽  
Model Species ◽  
Short Biography ◽  
Cell Niche ◽  
Over Time

Abstract In this work we discuss the concepts of the quiescent centre (QC) of the root apical meristem (RAM) and their change over time, from their formulation by F.A.L. Clowes to the present. This review is dedicated to the 100 th anniversary of the birth of Clowes, and we present his short biography and full bibliography of Clowes’ work. Over time, the concept of the QC proved to be useful for the understanding of RAM organization and behaviour. We focus specifically on conceptual developments, from the organization of the QC to understanding its functions in RAM maintenance and activity, ranging from a model species, Arabidopsis thaliana, to crops. Concepts of initial cells, stem cells, and heterogeneity of the QC cells in context of functional and structural stem cells are considered. We review the role of the QC in the context of cell flux in the RAM and the nature of quiescence of the QC cells. We discuss the origin of the QC and fluctuation of its size in ontogenesis and why the QC cells are more resistant to stress. Contemporary concepts of organizer and stem cell niche are also considered. We also propose how the stem cell niche in the RAM can be defined in roots of a non-model species.

Responses of plant vascular systems to auxin transport inhibition

Development ◽  
1999 ◽  
Vol 126 (13) ◽  
pp. 2979-2991 ◽  
Author(s):  
J. Mattsson ◽  
Z.R. Sung ◽  
T. Berleth
Keyword(s):  
Auxin Transport ◽  
Vascular Tissue ◽  
Vascular System ◽  
Leaf Margin ◽  
Vascular Pattern ◽  
Vascular Differentiation ◽  
Vascular Patterning ◽  
Transport Inhibitor ◽  
Auxin Transport Inhibitor

To assess the role of auxin flows in plant vascular patterning, the development of vascular systems under conditions of inhibited auxin transport was analyzed. In Arabidopsis, nearly identical responses evoked by three auxin transport inhibitor substances revealed an enormous plasticity of the vascular pattern and suggest an involvement of auxin flows in determining the sites of vascular differentiation and in promoting vascular tissue continuity. Organs formed under conditions of reduced auxin transport contained increased numbers of vascular strands and cells within those strands were improperly aligned. In leaves, vascular tissues became progressively confined towards the leaf margin as the concentration of auxin transport inhibitor was increased, suggesting that the leaf vascular system depends on inductive signals from the margin of the leaf. Staged application of auxin transport inhibitor demonstrated that primary, secondary and tertiary veins became unresponsive to further modulations of auxin transport at successive stages of early leaf development. Correlation of these stages to anatomical features in early leaf primordia indicated that the pattern of primary and secondary strands becomes fixed at the onset of lamina expansion. Similar alterations in the leaf vascular responses of alyssum, snapdragon and tobacco plants suggest common functions of auxin flows in vascular patterning in dicots, while two types of vascular pattern alterations in Arabidopsis auxin transport mutants suggest that at least two distinct primary defects can result in impaired auxin flow. We discuss these observations with regard to the relative contributions of auxin transport, auxin sensitivity and the cellular organisation of the developing organ on the vascular pattern.

Embryons somatiques de Vitis rupestris et embryons zygotiques de Vitis sp. : morphologie, histologie, histochimie et développement

1990 ◽  
Vol 68 (11) ◽  
pp. 2305-2315 ◽  
Author(s):  
Olivier Faure
Keyword(s):  
Somatic Embryos ◽  
Vascular System ◽  
Root Apex ◽  
Zygotic Embryos ◽  
Vitis Rupestris ◽  
Saturated Atmosphere ◽  
Vitis Sp ◽  
Water Saturated ◽  
Root Apices

The problem of the development of grapevine somatic embryos into plantlets was examined through a morphological, histological, and histochemical comparison of zygotic and somatic embryos. Only 3% of somatic embryos were capable of developing into plantlets. However, 27% of these embryos had shoot and root apices showing a histological pattern similar to that observed in zygotic embryos; other embryos had root apex but no shoot apex. In comparison with zygotic embryos, somatic embryos showed the following characteristics: acquisition of giant, and often teratologic, organs, retention of a high proliferative capacity among superficial cells, starch and tannin accumulation, important suberization and slight lignification of superficial cells, differentiation of tracheids in the vascular system, and preservation of a high embryogenic potential in the absence of exogenous growth regulators. The water-saturated atmosphere to which grapevine somatic embryos were submitted during in vitro culture could be unfavourable to germination. Under these conditions, embryos built impermeable suberized superficial layers. Key words: somatic embryos, zygotic embryos, Vitis sp., histochemistry, development.

Critical level of radiation damage of root apical meristem and mechanisms for its recovery in Pisum sativum L.

2011 ◽  
Vol 45 (1) ◽  
pp. 18-26 ◽  
Author(s):  
E. A. Kravets ◽  
A. N. Mikheev ◽  
L. G. Ovsyannikova ◽  
D. M. Grodzinsky
Keyword(s):  
Pisum Sativum ◽  
Radiation Damage ◽  
Apical Meristem ◽  
Critical Level ◽  
Root Apical Meristem ◽  
Pisum Sativum L

scholarly journals Sound Waves Promote Arabidopsis thaliana Root Growth by Regulating Root Phytohormone Content

2021 ◽  
Vol 22 (11) ◽  
pp. 5739
Author(s):  
Joo Yeol Kim ◽  
Hyo-Jun Lee ◽  
Jin A Kim ◽  
Mi-Jeong Jeong
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Division ◽  
Root Growth ◽  
Apical Meristem ◽  
Cell Number ◽  
Root Apical Meristem ◽  
Control Group ◽  
Auxin Signaling ◽  
Ethylene Signaling ◽  
Sound Waves

Sound waves affect plants at the biochemical, physical, and genetic levels. However, the mechanisms by which plants respond to sound waves are largely unknown. Therefore, the aim of this study was to examine the effect of sound waves on Arabidopsis thaliana growth. The results of the study showed that Arabidopsis seeds exposed to sound waves (100 and 100 + 9k Hz) for 15 h per day for 3 day had significantly longer root growth than that in the control group. The root length and cell number in the root apical meristem were significantly affected by sound waves. Furthermore, genes involved in cell division were upregulated in seedlings exposed to sound waves. Root development was affected by the concentration and activity of some phytohormones, including cytokinin and auxin. Analysis of the expression levels of genes regulating cytokinin and auxin biosynthesis and signaling showed that cytokinin and ethylene signaling genes were downregulated, while auxin signaling and biosynthesis genes were upregulated in Arabidopsis exposed to sound waves. Additionally, the cytokinin and auxin concentrations of the roots of Arabidopsis plants increased and decreased, respectively, after exposure to sound waves. Our findings suggest that sound waves are potential agricultural tools for improving crop growth performance.

scholarly journals AT-HOOK MOTIF NUCLEAR LOCALISED PROTEIN 18 as a Novel Modulator of Root System Architecture

2020 ◽  
Author(s):  
Marek Šírl ◽  
Tereza Šnajdrová ◽  
Dolores Gutiérrez-Alanís ◽  
Joseph G. Dubrovsky ◽  
Jean Phillipe Vielle-Calzada ◽  
...  
Keyword(s):  
Root System ◽  
System Architecture ◽  
Lateral Root ◽  
Apical Meristem ◽  
Lateral Roots ◽  
Primary Root ◽  
Root System Architecture ◽  
Root Apical Meristem ◽  
Root Initiation ◽  
Lateral Root Initiation

The AT-HOOK MOTIF NUCLEAR LOCALIZED PROTEIN (AHL) gene family encodes embryophyte-specific nuclear proteins with DNA binding activity. They modulate gene expression and affect various developmental processes in plants. We identify AHL18 (At3G60870) as a developmental modulator of root system architecture and growth. AHL18 regulates the length of the proliferation domain and number of dividing cells in the root apical meristem and thereby, cell production. Both primary root growth and lateral root development respond according to AHL18 transcription level. The ahl18 knock-out plants show reduced root systems due to a shorter primary root and a lower number of lateral roots. This change results from a higher number of arrested and non-developing lateral root primordia (LRP) rather than from decreased initiation. Overexpression of AHL18 results in a more extensive root system, longer primary roots, and increased density of lateral root initiation events. Formation of lateral roots is affected during the initiation of LRP and later development. AHL18 regulate root apical meristem activity, lateral root initiation and emergence, which is in accord with localization of its expression.

Regeneration of the root pole in surgically transected carrot embryos occurs by position-dependent, proximodistal replacement of missing tissues

Development ◽  
1991 ◽  
Vol 113 (4) ◽  
pp. 1305-1313 ◽  
Author(s):  
F.M. Schiavone ◽  
R.H. Racusen
Keyword(s):  
Apical Meristem ◽  
Surgical Margin ◽  
Longitudinal Axis ◽  
Root Apical Meristem ◽  
Original Structure ◽  
The Future ◽  
Embryo Cells ◽  
Varying Length ◽  
Original Size ◽  
Root Axis

Torpedo-stage carrot embryos were surgically transected at various locations along the shoot-root axis and explants of the cotyledon-bearing shoot pole were sectioned and examined in order to provide a more detailed description of root pole regeneration. When excisions occurred at the sites of the future hypocotyl, the future radicle or the future root apical meristem, the regenerating axial tissues exhibited patterns of cellular organization that were nearly identical to those seen in unsevered controls. To accomplish this restoration, new cells, of the type normally found at each cutting site, were produced behind a regeneration dome that formed over the original surgical site. The regeneration dome was displaced by division and expansion-driven extension of the longitudinal axis, and cells in the renewed region quickly acquired individual anatomical traits and collective tissue morphologies that corresponded to those of cells in the analogous locations in intact embryos. Although no clear mechanism is implied, the results of these experiments suggest that interactions between cells near the surgical margin permit them to retain their sense of location within the original structure, and apprise them of the removal of their basipetally positioned neighbors. With varying-length remnants of the shoot serving as the only vestige of the original size and shape of the embryo, cells close to the site of excision were apparently reconfigured to commence ordered divisions that ultimately reconstituted the embryonic axis.

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