Root apex structure in Ephedra nevadensis

1983 ◽  
Vol 61 (1) ◽  
pp. 267-278 ◽  
Author(s):  
R. L. Peterson
Keyword(s):  
Mitotic Index ◽  
Central Region ◽  
Root Apex ◽  
Root Cap ◽  
Quiescent Centre ◽  
Columella Cells ◽  
Ephedra Nevadensis ◽  
Peripheral Cells

The distinctive, large cells in the central region of the root apex of Ephedra nevadensis Wats. which do not incorporate [3H]thymidine and stain lightly with Feulgen reagent comprise the quiescent centre. These cells and adjacent meristem cells remain at the 2C–4C level of DNA. Ultrastructurally, cells of the quiescent centre are characterized by possessing proplastids, numerous ribosomes, small vacuoles, and few plasmodesmata. The root cap consists of a columella and periphery. Nuclei of columella cells are either at the 2C or 4C level of DNA as determined by microspectrophotometry. The mitotic index remains high up to 50 cell tiers from the quiescent centre – root cap boundary. Starch deposition is delayed considerably in columella cells but not in peripheral cells. The root cap of this genus is unique in its method of growth.

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.

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.

Identification of Periplasmic Root-Cap Mucilage in Developing Columella Cells of Arabidopsis thaliana

2019 ◽  
Vol 60 (6) ◽  
pp. 1296-1303 ◽  
Author(s):  
Kazuki Maeda ◽  
Tadashi Kunieda ◽  
Kentaro Tamura ◽  
Kyoko Hatano ◽  
Ikuko Hara-Nishimura ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Root Cap ◽  
Columella Cells

scholarly journals Morphoanatomic changes in shoot and root apices of banana Williams (AAA, Musa sp.) cultured on different N6- benzyladenine concentrations

1969 ◽  
Vol 92 (1-2) ◽  
pp. 53-72
Author(s):  
Maribel Ramírez-Villalobos ◽  
Helga Lindorf ◽  
Eva De García
Keyword(s):  
Lateral Roots ◽  
Root Apex ◽  
Transitional Zone ◽  
Root Cap ◽  
Anatomic Structure ◽  
Musa Sp ◽  
Tunica Layer ◽  
Vitro Development ◽  
Root Apices

Structural evidence about the in vitro growth of the shoot apex (SA) and root apex (RA) of banana is for the most part lacking.This paper presents an analysis of the morphoanatomic events that occur in the in vitro development of the SA, RA and explants of banana Williams cultured under different N6-benzyladenine (BA) concentrations. We examined the SA of explants (8 mm X 1.5 mm, shoot tip with part of rhizome) grown on 0, 2.5 and 5 mg /L of BA for 0, 3, 6, 9 and 12 d, and also the first emergent root (1 to 1.5 cm long) from these explants. Samples were sectioned (10 to 12 µm) and stained with safranin-fast green. The SA showed a dome shape with tunica-corpus organization (a single tunica layer). SA diameters were larger for explants growing in BA (93.75 to 142.05 µm) than in those growing without the cytokinin (73.87 to 85.83 µm), except for the diameter on the sixth day (127.84 µm). The noncultured initial explant without culture reached a diameter of 164.78 µm. The SA showed a cambium-like transitional zone in explants cultured with 2.5 mg/L of BA on the ninth day. This concentration also induced the highest number of shoots per explant (2.19) in 35 days. RA growing in media without BA showed protoderm, ground meristem, procambium, initial cells and root cap whereas with BA procambium, fundamental meristem and root cap (compressed) were distinguished. Benzyladenine decreased the number and length of the roots, inhibited the formation of lateral roots, increased the time for root emergence and caused distortion in their anatomic structure.

Localisation of aluminium in root apex cells of two Australian perennial grasses by X-ray microanalysis

1998 ◽  
Vol 25 (4) ◽  
pp. 427 ◽  
Author(s):  
Simon A. Crawford ◽  
Alan T. Marshall ◽  
Sabine Wilkens
Keyword(s):  
Significant Positive Correlation ◽  
Root Apex ◽  
Root Cap ◽  
Perennial Grasses ◽  
Elemental Distribution ◽  
X Ray ◽  
Positive Correlation ◽  
Distribution Maps ◽  
Meristematic Cells ◽  
Root Apices

To determine if an increased aluminium (Al) sensitivity is the result of greater accumulation of Al in root apices, the quantity and distribution of Al in root apex cells of Danthonia linkii Kunth and Microlaena stipoides (Labill.) R.Br. was investigated by X-ray microanalysis. Seedlings were grown in nutrient solution with 0, 185 and 370 µM total Al for 24 h after which the terminal 5 mm of the roots were excised, rapidly frozen and embedded using freeze-substitution. Elemental distribution maps of root apices showed that Al had accumulated in the nuclei of root cap and meristematic cells in Al-stressed roots of D. linkii but not in M. stipoides. Al appeared to be co-localised with phosphorous (P) in the nuclei of these cells. Quantitation of Al revealed that Al-stressed root apex cells of D. linkiiaccumulated significantly more Al than M. stipoides. Exposure of D. linkii roots to Al resulted in substantial increases in the P content of root apex cells, and a significant positive correlation was found between Al and P in both root cap and meristematic cells. Analysis of intracellular structures showed that the majority of Al had accumulated in the nuclei of cells. A significant positive correlation was found between Al and P in the nuclei, but not in the cytoplasm or cell walls. No positive correlation was found between Al and P in root apex cells of M. stipoides.

INFLUENCE OF MICROGRAVITY ON ROOT-CAP REGENERATION AND THE STRUCTURE OF COLUMELLA CELLS IN ZEA MAYS

1987 ◽  
Vol 74 (2) ◽  
pp. 218-223 ◽  
Author(s):  
Randy Moore ◽  
C. Edward McClelen ◽  
W. Mark Fondren ◽  
Chia-Lien Wang
Keyword(s):  
Zea Mays ◽  
Root Cap ◽  
Columella Cells

scholarly journals Apoplastic histochemical features of plant root walls that may facilitate ion uptake and retention

2021 ◽  
Vol 16 (1) ◽  
pp. 1347-1356
Author(s):  
Di Wu ◽  
Linbao Li ◽  
Chengdao Li ◽  
Bicheng Dun ◽  
Jun Zhang ◽  
...  
Keyword(s):  
Plant Root ◽  
Root Apex ◽  
Pteris Vittata ◽  
Root Cap ◽  
Pistia Stratiotes ◽  
Epifluorescence Microscopy ◽  
Alternanthera Philoxeroides ◽  
Indigenous Plants ◽  
Invasion Mechanisms

Abstract We used brightfield and epifluorescence microscopy, as well as permeability tests, to investigate the apoplastic histochemical features of plant roots associated with ion hyperaccumulation, invasion, and tolerance of oligotrophic conditions. In hyperaccumulator species with a hypodermis (exodermis absent), ions penetrated the root apex, including the root cap. By contrast, in non-hyperaccumulator species possessing an exodermis, ions did not penetrate the root cap. In vivo, the lignified hypodermis blocked the entry of ions into the cortex, while root exodermis absorbed ions and restricted them to the cortex. The roots of the hyperaccumulators Pteris vittata and Cardamine hupingshanensis, as well as the aquatic invasives Alternanthera philoxeroides, Eichhornia crassipes, and Pistia stratiotes, contained lignin and pectins. These compounds may trap and store ions before hypodermis maturation, facilitating ion hyperaccumulation and retention in the apoplastic spaces of the roots. These apoplastic histochemical features were consistent with certain species-specific characters, including ion hyperaccumulation, invasive behaviors in aquatic environments, or tolerance of oligotrophic conditions. We suggest that apoplastic histochemical features of the root may act as invasion mechanisms, allowing these invasive aquatic plants to outcompete indigenous plants for ions.

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