The secondary phloem of Austrobaileya scandens

1970 ◽  
Vol 48 (2) ◽  
pp. 341-359 ◽  
Author(s):  
Lalit M. Srivastava
Keyword(s):  
Tannic Acid ◽  
Cross Sections ◽  
Significant Proportion ◽  
Sieve Tube ◽  
Secondary Phloem ◽  
Sieve Elements ◽  
Sieve Cells ◽  
Companion Cells ◽  
Parenchyma Cells ◽  
Definition Of

The origin of sieve elements and parenchyma cells in the secondary phloem of Austrobaileya was studied by use of serial cross sections stained with tannic acid – ferric chloride and lacmoid. In three important respects, Austrobaileya phloem recalls gymnospermous features: it has sieve cells rather than sieve-tube members; a significant proportion of sieve elements and companion cells arise independently of each other; and sieve areas occur between sieve elements and companion cells ontogenetically unrelated to each other. The angiospermous feature includes origin of most sieve elements and parenchyma, including companion cells, after divisions in phloic initials. In these instances companion cells show a closer ontogenetic relationship to sieve elements than do other parenchyma cells. The combination of gymnospermous and angiospermous features makes phloem of Austrobaileya unique when compared to that of all those species that have been investigated in detail. It is further suggested that the term albuminous cells is inappropriate and should be replaced by companion cells but that the ontogenetic relationship implicit in the definition of companion cells is too restrictive and should be abandoned.

Fine structure of the phloem of Pisum sativum. II. The companion cell and phloem parenchyma

1965 ◽  
Vol 13 (2) ◽  
pp. 185
Author(s):  
MC Wark
Keyword(s):  
Fine Structure ◽  
Sieve Element ◽  
Companion Cell ◽  
Secondary Phloem ◽  
Sieve Elements ◽  
Phloem Parenchyma ◽  
Wall Structures ◽  
Companion Cells ◽  
Parenchyma Cells ◽  
Vacuolated Cells

The companion cells of the secondary phloem of Pisum contain all the organelles characteristic of cells possessing an active metabolism. The cytoplasm of the companion cells shows little change during ontogeny. Complex plasmodesmata connect the sieve elements and companion cells. These are the only connections observed between the sieve elements and other phloem cells. New wall structures of the companion cells are described. These structures are here tentatively called trabeculae; they intrude into the cytoplasm, but never completely cross the cell. The trabeculae alter in appearance at the time when the sieve element nucleus and tonoplast disappear. The phloem parenchyma cells are large vacuolated cells wider in diameter but shorter in length than the sieve elements. They contain all the organelles found in normal photosynthetic tissue. The cytoplasm of the phloem parenchyma shows little change during ontogeny. Plasmodesmata of well-developed pit fields connect the phloem parenchyma with the companion cells. The phloem parenchyma does not communicate with the sieve elements.

Comparative Anatomy of the Secondary Phloem of Ten Species of Rosaceae

IAWA Journal ◽  
1993 ◽  
Vol 14 (3) ◽  
pp. 289-298 ◽  
Author(s):  
Liu Donghua ◽  
Gao Xinzeng
Keyword(s):  
Comparative Anatomy ◽  
Secondary Phloem ◽  
Sieve Elements ◽  
Companion Cells ◽  
Parenchyma Cells ◽  
Sieve Plates ◽  
Lateral Walls

The anatomy of the secondary phloem of species belonging to four genera in Rosaceae is described. The three genera of the Maloideae studied are more or less similar in their phloem anatomy; tangential bands of fibresclereids alternate with bands of sieve elements, companion cells and parenchyma cells; superficially, the nonconducting and conducting phloem are not distinct from one another; sieve plates are compound and there are conspicuous sieve areas on lateral walls; rays are uniseriate and multiseriate, and homocellular. In the five species of Prunus (Prunoideae) studied, there are no fibre-sclereids in the conducting phloem, end walls bearing simple sieve plates are oblique to nearly horizontal; and rays are uniseriate and multiseriate, homocellular.

Ontogeny of phloem transfer cells in Hieracium floribundum

1975 ◽  
Vol 53 (23) ◽  
pp. 2745-2758 ◽  
Author(s):  
R. L. Peterson ◽  
E. C. Yeung
Keyword(s):  
Cell Types ◽  
Transfer Cells ◽  
Vascular Cambium ◽  
Secondary Phloem ◽  
Sieve Elements ◽  
Wall Ingrowths ◽  
Wall Ingrowth ◽  
Companion Cells ◽  
Parenchyma Cells ◽  
Cambium Activity

The primary phloem system in the rhizome of Hieracium floribundum has transfer cells that have developed from companion cells and parenchyma cells, which are adjacent to sieve elements. In both cell types changes occur in the cytoplasmic organelles at the time of wall ingrowth formation. Dicytosomes and polyribosomes become more numerous and 'boundary formations' and other multivesiculated structures appear. Few microtubules were found in the cytoplasm at this time. After the wall ingrowths become obvious, the transfer cells develop numerous mitochondria and an enlarged nucleus. The phloem transfer cells become vacuolated with age and the wall ingrowths become less numerous. This may be associated with a change in the translocation pattern in the phloem after the inception of vascular cambium activity. Parenchyma cells in the secondary phloem usually become rather vacuolated and develop few wall ingrowths.

Structure of Wood and Cambial Variant in the Stem of Dalbergia Paniculata Roxb.

IAWA Journal ◽  
1990 ◽  
Vol 11 (4) ◽  
pp. 379-391 ◽  
Author(s):  
M. N. B. Nair ◽  
H. Y. Mohan Ram
Keyword(s):  
Succinate Dehydrogenase ◽  
Dehydrogenase Activity ◽  
Sieve Tube ◽  
Secondary Phloem ◽  
Succinate Dehydrogenase Activity ◽  
Successive Cambia ◽  
Phloem Parenchyma ◽  
Companion Cells ◽  
Parenchyma Cells ◽  
Cambial Variant

The wood of Dalbergia paniculata is unique as it consists of concentric layers of broad xylem, alternating with bands of narrow phloem. This anomaly results from the periodic formation of successive cambia in the secondary phloem. Some phloem parenchyma cells dedifferentiate to form a discontinuous ring of cambium. Such parenchyma cells have higher succinate dehydrogenase activity than the neighbouring cells of secondary phloem. The newly differentiated cambial layer functions bidirectionally, and its products give rise to xylem internally and phloem externally. The phloem along with cambium present internal to the newly formed xylem becomes included.The wood is diffuse-porous and the intervessel pits are vestured. The phloem has welldifferentiated sieve tube members and companion cells.

Structure of Stem and Cambial Variant in Spatholobus Roxburgii (Leguminosae)

IAWA Journal ◽  
1993 ◽  
Vol 14 (2) ◽  
pp. 191-204 ◽  
Author(s):  
M.N.B. Nair
Keyword(s):  
Vascular Tissue ◽  
Secondary Growth ◽  
Sieve Tube ◽  
Secretory Cells ◽  
Secondary Phloem ◽  
Phloem Parenchyma ◽  
Companion Cells ◽  
Parenchyma Cells ◽  
Ray Cells ◽  
Cambial Variant

The stern of Spatholobus roxburghii, a tropicalliana, has alternating layers of xylem and phloem as a result of formation and activity of successive cambia. Successive cambial rings are developed by dedifferentiation of groups of parenchyma cells outside the discontinuous band of sclereid-fibres. The sclereid- fibre band is formed by the development of sclereids between the primary bark fibres. Each successive cambium first produces a layer of sclereid-fibres which separates the vascular tissue produced by one cambial ring from the other. After secondary growth, the epidermis is replaced by periderm. In the older stern phelloderm contributes to the formation of new cambiallayers. Secondary phloem has sieve tube members; companion cells, phloem parenchyma, phloem fibres and secretory cells. The wood shows a tendency towards ring-porosity only in the first xylem layer. The subsequent layers are diffuseporous. The vessels are wide and narrow. Perforated ray cells or radial vessels are frequent in the wood and probably help in vertical conduction by interconnecting vessel endings. In this scandent species parenchyma cells are abundant. It is inferred that they help the vessel segments to remain undamaged when the woody stern twists around supports.

Anatomy and Chemical Composition of Pinus Pinaster Bark

IAWA Journal ◽  
1996 ◽  
Vol 17 (2) ◽  
pp. 141-150 ◽  
Author(s):  
Elsa Nunes ◽  
Teresa Quilhó ◽  
Helena Pereira
Keyword(s):  
Chemical Composition ◽  
Pinus Pinaster ◽  
Variable Number ◽  
Starch Granules ◽  
Secondary Phloem ◽  
Scale Type ◽  
Resin Ducts ◽  
Sieve Cells ◽  
Parenchyma Cells

The secondary phloem of Pinus pinaster Aiton bark has sieve cells and axial and radial parenchyma, but no fibres. Resin ducts are present in fusiform rays . Stiloid crystals, starch granules and tannins occur inside sieve and parenchyma cells. The rhytidome of P. pinaster bark has a variable number of periderms forming scale-type discontinuous layers over expanded parenchyma cells. Phellem comprises 4-6 layers of thickwaIled and little suberized cells and phelloderm a layer of 2 or 3 thickened lignified ceIls and a layer of expanded cells.

Fine structure of the primary root phloem of Pisum

1968 ◽  
Vol 16 (1) ◽  
pp. 37 ◽  
Author(s):  
SY Zee ◽  
TC Chambers
Keyword(s):  
Primary Root ◽  
Root Apex ◽  
Sieve Element ◽  
Cross Wall ◽  
Secondary Phloem ◽  
Sieve Elements ◽  
Phloem Parenchyma ◽  
Pisum Sativum L ◽  
Companion Cells ◽  
Stem Internode

The morphogenesis of the sieve elements, companion cells, and phloem parenchyma in the region between 0.5 and 2.0 mm from the actively growing root apex of seedlings of Pisum sativum L. cv. Telephone is described. The overall developmental pattern is essentially similar to that already described for the secondary phloem of the young stem internode of the same species, although differences in the development of some organelles do exist between the two types of phloem. The development of the sieve element is traced from the earliest stages of cross wall formation up to the morphologically mature stages. Very few sieve elements reach morphological maturity in this region. The possibility that the functional translocatory sieve elements are those at earlier stages of development is discussed.

Sugar beet petiole structure: vascular anastomoses and phloem ultrastructure

1985 ◽  
Vol 63 (12) ◽  
pp. 2295-2304 ◽  
Author(s):  
John W. Oross ◽  
William J. Lucas
Keyword(s):  
Endoplasmic Reticulum ◽  
Sugar Beet ◽  
Vascular Anatomy ◽  
Initial Contact ◽  
Lateral Movement ◽  
Sieve Elements ◽  
Phloem Parenchyma ◽  
Microfilament Bundles ◽  
Companion Cells ◽  
Parenchyma Cells

The vascular anatomy and phloem ultrastructure of the sugar beet petiole were studied in an attempt to evaluate the potential of petiolar phloem anastomoses to accommodate lateral movement of translocates across this structure. Clearings revealed that six of the eight interveinal regions between the nine major, axially oriented veins were connected by many anastomoses. The two interveinal areas characterized by the fewest anastomoses were located near the margin of the petiole. It was concluded that lateral translocation via anastomoses would be most efficient in the central part of the petiole. A light microscope study of the structure of the junction between anastomosing and continuous veins revealed that the sieve elements of each of the merging veins were separated from each other, for distances of up to 6 mm beyond the point of initial contact, by phloem parenchyma cells. The presence of phloem parenchyma cells in this position, and between the clusters of sieve elements that occur across the phloem of the large bundles, was taken as an indication that the parenchyma cells may have an important role in lateral translocation. An ultrastructural study of the petiolar phloem revealed that the phloem parenchyma and companion cells could be easily distinguished on the basis of the structure of the chloroplasts, dictyosomes, and endoplasmic reticulum. Microfilament bundles and spine-coated tubules and (or) vesicles were uniquely present in the parenchyma cells. The ultrastructure of the phloem parenchyma cells is discussed relative to their possible role in mediating the movement of sugars through the anastomoses.

scholarly journals RELATION OF BEET YELLOWS VIRUS TO THE PHLOEM AND TO MOVEMENT IN THE SIEVE TUBE

1967 ◽  
Vol 32 (1) ◽  
pp. 71-87 ◽  
Author(s):  
K. Esau ◽  
J. Cronshaw ◽  
L. L. Hoefert
Keyword(s):  
Sieve Tube ◽  
Plant Viruses ◽  
Passive Transport ◽  
Sieve Elements ◽  
Virus Particles ◽  
Parenchyma Cells ◽  
Beet Yellows Virus ◽  
Sieve Tubes ◽  
Sieve Plates ◽  
Orderly Arrangement

In minor veins of leaves of Beta vulgaris L. (sugar beet) yellows virus particles were found both in parenchyma cells and in mature sieve elements. In parenchyma cells the particles were usually confined to the cytoplasm, that is, they were absent from the vacuoles. In the sieve elements, which at maturity have no vacuoles, the particles were scattered throughout the cell. In dense aggregations the particles tended to assume an orderly arrangement in both parenchyma cells and sieve elements. Most of the sieve elements containing virus particles had mitochondria, plastids, endoplasmic reticulum, and plasma membrane normal for mature sieve elements. Some sieve elements, however, showed evidence of degeneration. Virus particles were present also in the pores of the sieve plates, the plasmodesmata connecting the sieve elements with parenchyma cells, and the plasmodesmata between parenchyma cells. The distribution of the virus particles in the phloem of Beta is compatible with the concept that plant viruses move through the phloem in the sieve tubes and that this movement is a passive transport by mass flow. The observations also indicate that the beet yellows virus moves from cell to cell and in the sieve tube in the form of complete particles, and that this movement may occur through sieve-plate pores in the sieve tube and through plasmodesmata elsewhere.

scholarly journals Morphological, Anatomical and Palynological Studies on Endemic Matthiola anchoniifolia Hub. -Mor. (Brassicaceae)

2013 ◽  
Vol 5 (2) ◽  
pp. 163-168 ◽  
Author(s):  
Mehmet TEKIN ◽  
Gülden YILMAZ ◽  
Esra MARTIN
Keyword(s):  
Cross Sections ◽  
Anatomical Study ◽  
Endemic Plant ◽  
Exine Ornamentation ◽  
Companion Cells ◽  
Parenchyma Cells ◽  
Sieve Tubes ◽  
Pollen Shape ◽  
Periclinal Walls ◽  
First Time

In this paper, anatomical, palynological and seed micromorphological properties of an endemic plant Matthiola anchoniifolia Hub.-Mor. are recorded for the first time. A description and descriptive illustrations of the species are given based on the collected specimens for morphological study. Seed surface of M. anchoniifolia is examined by scanning electron microscope. The seed of M. anchoniifolia was compressed, brownish in colour and the cells of testa were nearly 60-80 μm in diameter and ranged from isodiametric, tetragonal or pentagonal. The anticlinal walls were straight or weakly curved while the outer periclinal walls were concave to flat with smooth surface. In anatomical study, cross sections of root, stem and stem leaf are examined. The root had secondary structure. Periderm consists of 5-8 layers of cells for phellem. Cortex consists of 9-12 layered parenchymatic tissue under the periderm. Secondary phloem ring-shaped, 6-9 layered and consists of companion cells and grouped sieve tubes. Stem had primary structure when analyzed. It is circular with a few irregular ribs in cross section. Cortex is 8-12 layered and parenchymatous. Stoma cells are present on both epidermis. Leaf is isobilateral. There are unicellular and ramified hairs on both surface. Palisade parenchyma cells are 1-2 layered and spongy parenchyma cells are 5-12 layered. M. anchoniifolia has tricolpate pollen type, prolate pollen shape and reticulate exine ornamentation.

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