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.

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.

scholarly journals Asymmetric wall ingrowth deposition in Arabidopsis phloem parenchyma transfer cells is tightly associated with sieve elements

2022 ◽  
Author(s):  
Xiaoyang Wei ◽  
Yuan Huang ◽  
David A Collings ◽  
David W McCurdy
Keyword(s):  
Cell Types ◽  
Phloem Loading ◽  
Transfer Cells ◽  
Companion Cell ◽  
Wall Ingrowths ◽  
Phloem Parenchyma ◽  
Wall Ingrowth ◽  
Functional Differences ◽  
Transgenic Lines ◽  
Different Cell Types

In Arabidopsis, polarized deposition of wall ingrowths in phloem parenchyma (PP) transfer cells (TCs) occurs adjacent to cells of the sieve element/companion cell (SE/CC) complex. However, the spatial relationships between these different cell types in minor veins, where phloem loading occurs, are poorly understood. PP TC development and wall ingrowth localization were compared to other phloem cells in leaves of Col-0 and the transgenic lines AtSUC2::AtSTP9-GFP and AtSWEET11::AtSWEET11-GFP that identify CCs and PP respectively. The development of PP TCs in minor veins, indicated by deposition of wall ingrowths, proceeded basipetally in leaves. However, not all PP develop ingrowths and higher levels of wall ingrowth deposition occur in abaxial- compared to adaxial-positioned PP TCs. Furthermore, the deposition of wall ingrowths was exclusively initiated on and preferentially covered the PP TC/SE interface, rather than the PP TC/CC interface, and only occurred in PP cells that were adjacent to SEs. Collectively, these results demonstrate the dominant impact of SEs on wall ingrowth deposition in PP TCs and suggest the existence of two sub-types of PP cells in leaf minor veins. Compared to PP cells, PP TCs showed more abundant accumulation of AtSWEET11-GFP, indicating functional differences in phloem loading between PP and PP TCs.

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.

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.

Developmental anatomy of natural root grafts in Ficus globosa

1966 ◽  
Vol 14 (3) ◽  
pp. 269 ◽  
Author(s):  
AN Rao
Keyword(s):  
Secondary Growth ◽  
Vascular Cambium ◽  
Initial Contact ◽  
Secondary Phloem ◽  
Developmental Anatomy ◽  
Single Root ◽  
Aerial Roots ◽  
Parenchyma Cells ◽  
Ray Cells ◽  
Root Grafts

The series of events, and the anatomical changes connected with them, leading to the fusion of aerial roots in Ficus globosa Blume are described. The initial contact between two aerial roots is estabiished by the formation and fusion of epidermai hairs. Secondary growth increases the size of the roots, and consequently the cortices of the two adjacent roots approach one another and become compressed. The cortical tissues thin out in the central region of the compressed zone, but fuse marginally and remain intact. In both roots the ray cells near the contact area become highly meristematic; by active division they produce many parenchyma cells that extend towards each other and finally merge to establish a continuous parenchymatous zone between the steles of the two roots. The cortical tissues, secondary phloem, and vascular cambium in both roots are interrupted by the formation of this new tissue. Later some of the parenchyma cells below the fused regions of the cortex redifferentiate into vascular cambium and extend laterally, joining the pre-existing, interrupted cambia of the two roots. Thus a continuous ring of vascular cambium is reorganized that gives rise to more secondary xylem and phloem. Cork cambium differentiates in the subepidermal layers to form a thick periderm with a smooth surface, so that the fused roots appear externally as a single root. Certain important points of the present study are discussed with reference to previous work.

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.

Transfer Cells in the Root Epidermis of Atriplex hastata L. As a Response to Salinity: a Comparative Cytological and X-Ray Microprobe Investigation

1978 ◽  
Vol 5 (6) ◽  
pp. 739 ◽  
Author(s):  
D Kramer ◽  
WP Anderson ◽  
J Preston
Keyword(s):  
Root Apex ◽  
Transfer Cells ◽  
Cytological Investigation ◽  
Xylem Parenchyma ◽  
Salt Treatment ◽  
Selective Uptake ◽  
X Ray ◽  
Root Epidermis ◽  
Wall Ingrowths ◽  
Parenchyma Cells

A cytological investigation has been made of the roots of the halophyte Atriplex hastata L. Transfer cells developed in the epidermis in response to salt treatment. They occurred only in a zone 1-3 mm behind the root apex and possessed a labyrinth only in their outer tangential walls (facing the root environment). When the epidermis was damaged, the adjacent exodermal cells then developed wall ingrowths in saline conditions. Ontogenetically this differentiation is correlated with the formation of the Casparian strip and the disintegration of the vessel contents. The X-ray microanalysis data on deep-frozen hydrated root specimens indicate that the epidermal transfer cells concentrate K+, and exclude Cl-, relative to the medium. It is concluded that the epidermal transfer cells function in selective uptake of K+ which is subsequently transported laterally into the stele and secreted into the vessels by the xylem parenchyma cells.

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