Reaction of Western Ironweed Leaf Tissue to Picloram

Weed Science ◽  
1968 ◽  
Vol 16 (3) ◽  
pp. 347-349 ◽  
Author(s):  
C. J. Scifres ◽  
M. K. McCarty
Keyword(s):  
Vascular Bundle ◽  
Leaf Tissue ◽  
Sieve Elements ◽  
Phloem Parenchyma ◽  
Cell Destruction ◽  
Companion Cells ◽  
Meristematic Activity

Foliar treatments of 4-amino-3,5,6-trichloropicolinic acid (picloram) induced rapid procambium activity in western iron-weed (Vernonia baldwini Torr.) leaves. Increased meristematic activity was followed by destruction of the phloem parenchyma, sieve elements, and companion cells. Cell destruction in the vascular bundle was concomitant with that in the mesophyll.

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.

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.

Plastids and mitochondria in the phloem of Cucurbita

1968 ◽  
Vol 46 (7) ◽  
pp. 877-880 ◽  
Author(s):  
Katherine Esau ◽  
James Cronshaw
Keyword(s):  
Cell Maturation ◽  
Cucurbita Maxima ◽  
Starch Grains ◽  
Sieve Elements ◽  
Phloem Parenchyma ◽  
Companion Cells ◽  
Structural Abnormalities ◽  
Parenchyma Cells ◽  
The Matrix

Contrary to some statements in the literature, the sieve elements of Cucurbita maxima Duchesne contain plastids. In young cells these organelles resemble mitochondria with regard to size and density of the matrix; but they have fewer internal membranes. During cell maturation, the plastids enlarge and their contents become thin and electron-transparent. They assume a partly degenerated appearance and do not deposit starch. The plastids of the companion cells resemble those of the young sieve elements but develop a considerable number of internal membranes, which may be organized into typical chloroplast grana. Starch is rarely encountered in these plastids. The plastids of the phloem-parenchyma cells are chloroplasts, commonly including starch grains. The mitochondria are similar in the three categories of cell but those of the sieve elements may show a denser matrix in young cells and structural abnormalities in mature cells.

The Fine Structure of Phloem Cells

1985 ◽  
Vol 43 ◽  
pp. 632-635
Author(s):  
James Cronshaw
Keyword(s):  
Structural Studies ◽  
High Concentration ◽  
Long Distance ◽  
Phloem Tissue ◽  
Sieve Elements ◽  
Long Distance Transport ◽  
P Protein ◽  
Companion Cells ◽  
Electron Microscopical ◽  
Distance Transport

Long distance transport in plants takes place in phloem tissue which has characteristic cells, the sieve elements. At maturity these cells have sieve areas in their end walls with specialized perforations. They are associated with companion cells, parenchyma cells, and in some species, with transfer cells. The protoplast of the functioning sieve element contains a high concentration of sugar, and consequently a high hydrostatic pressure, which makes it extremely difficult to fix mature sieve elements for electron microscopical observation without the formation of surge artifacts. Despite many structural studies which have attempted to prevent surge artifacts, several features of mature sieve elements, such as the distribution of P-protein and the nature of the contents of the sieve area pores, remain controversial.

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 Expression of GFP-fusions in Arabidopsis companion cells reveals non-specific protein trafficking into sieve elements and identifies a novel post-phloem domain in roots

2004 ◽  
Vol 41 (2) ◽  
pp. 319-331 ◽  
Author(s):  
Ruth Stadler ◽  
Kathryn M. Wright ◽  
Christian Lauterbach ◽  
Gabi Amon ◽  
Manfred Gahrtz ◽  
...  
Keyword(s):  
Protein Trafficking ◽  
Specific Protein ◽  
Sieve Elements ◽  
Companion Cells

Light microscopy survey of extant gymnosperm root protophloem and comparison with basal angiosperms

Botany ◽  
2014 ◽  
Vol 92 (5) ◽  
pp. 388-401 ◽  
Author(s):  
Thomas C. Pesacreta ◽  
Michael A. Purpera
Keyword(s):  
Root Apex ◽  
Cell Types ◽  
Tissue Type ◽  
Root Tip ◽  
Chemical Fixation ◽  
Physiological Mechanisms ◽  
Sieve Elements ◽  
Phloem Parenchyma ◽  
Extant Species ◽  
Large Central Vacuole

Gymnosperm root protophloem is not well understood. There is a question as to whether root protophloem cells mature as phloem parenchyma, or as sieve elements, or if within the protophloem there is an anatomical and evolutionary gradient having characteristics of both cell types. This question is relevant to understanding anatomical and physiological mechanisms that supply nutrients to the root tip. Anatomical data from a broad range of species show that gymnosperms have one to three layers of parenchymatous protophloem cells located at the vascular cylinder periphery between the pericyle and the metaphloem. In some species, these cells are associated with secretory idioblasts. Near the root apex, protophloem cells develop a large central vacuole and, in transverse sections, their radial walls tend to be radially elongated. When mature, these cells are highly longitudinally elongated. Only these cells exhibit surging toward the root apex during chemical fixation. These data indicate that protophloem of gymnosperm roots lacks sieve elements. Because of its distinctive anatomical characteristics and the absence of sieve elements, gymnosperm root protophloem is a vegetative synapomorphy among extant species. The restriction of this tissue type to gymnosperms supports the hypothesis that it originated in a progenitor of that clade.

Plastids in sieve elements and their companion cells

Planta ◽  
1973 ◽  
Vol 110 (4) ◽  
pp. 321-328 ◽  
Author(s):  
Heinz-Dietmar Behnke
Keyword(s):  
Sieve Elements ◽  
Companion Cells
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