Vessel elements

Vessel element of Perforated cell with Rapid transport of water... 

Xylem Tracheids, vessel elements, Conduction of water and minerals ... 

Figure 6. Longitudinal section showing the yellow-tan, anisotropic material that typically forms the remnant vessel walls in the coalified Persea wood. The contact between two vessel elements is shown with the dark red-brown tylose wall material in contact with the upper vessel element wall and extending across the perforation plate area into the lower element. 784X...

Figure 16. Types of vessel segments found in hardwoods. A and B springwood vessels from a ring-porous wood. Note the short length compared with the diameter. C and D typical vessel elements from diffuse-porous woods with simple perforation plates at each end. E typical diffuse-porous vessel element with scalariform perforation plates at each end. 140X...

Muller M (1980) Beitrag zum Einsatz der Curie Punkt-Pyrolyse Massenspektrometrie in der Analytik von Naturstoffen Dissertation ETH 6743, Zurich Obst JR (1983) Analytical pyrolysis of hardwood and softwood lignins and its use in lignin type determination of hardwood vessel elements J Wood Sci Technol 3 377-397 Pouwels AD, Boon JJ (1987) Analysis of lignin and chlorohgntn residues in a beech xylan fraction by pyrolysis gas chromatography mass spectrometry J Wood Sci Technol 7 197— 213... 

The movement of water and nutrients from the soil to the upper portions of a plant occurs primarily in the xylem. The xylem sap usually contains about 10 mol m-3 (10 mM)2 inorganic nutrients plus organic forms of nitrogen that are metabolically produced in the root. The xylem is a tissue of various cell types that we will consider in more detail in the final chapter (Section 9.4B,D), when water movement in plants is discussed quantitatively. The conducting cells in the xylem are the narrow, elongated tracheids and the vessel members (also called vessel elements), which tend to be shorter and wider than the tracheids. Vessel members are joined end-to-end in long... 

For application of Poiseuille s law to a complex tissue such as the xylem, care must be taken to ensure that particular vessel elements or tracheids are conducting (e.g., not blocked by embolisms), the actual radii must be determined (note the r4 dependence iiiEq. 9.11a), and corrections may be necessary for lumen shape, tracheid taper, and cell wall characteristics including pits (Calkin et al., 1986 Schulte et al., 1989a). For instance, if the lumen is elliptical with major and minor axes of a and b, respectively, then r4 in Equation 9.11a should be replaced by a3b3/ (8a2 + 8b2). 

All cells in the cambial zone are living. However, as xylem derivatives (i.e., developing wood cells) begin a sequence of transformations that will convert them into mature wood elements, they embark on a path of cell specialization or differentiation that will lead eventually (for fibers, vessel elements, and certain other cells) to cell death. 

During the division and enlargement phases of wood cell development, the cell wall is a thin, deformable, and extensible envelope of material referred to as the primary wall. Near the cessation of cell enlargement, however, a secondary wall may begin to be manufactured to the lumen side of the primary wall. Wood fibers, vessel elements, and certain other xylem or phloem elements that function in passive conduction and/or support normally develop a secondary wall (Figure 5). 

A. Fibers 1. Libriform fibers 2. Fiber tracheids 3. Vasicentric tracheids B. Axial parenchyma C. Vessel elements Ray parenchyma 1. Procumbent cells 2. Upright cells Homocellular rays 1 or 2 Heterocellular rays 1 and 2... 

Sculpturing. Pits. Softwood and hardwood fibers have closed ends, but a special wall feature facilitates movement of the tree s sap stream from one fiber to another, from fibers to vessel elements, and from fibers to ray cells. This special feature is a small opening or recess in the fiber secondary wall known technically as a pit. 

Vessel Elements. Architecture. The cell wall of vessel elements appears to be constructed along the same general scheme as wood fibers. However, the layering is generally more complicated, and the presence in many species of numerous intervessel bordered... 

Sculpturing. Pits, The regions on vessel elements where contact is made with adjacent vessels, fibers, and parenchyma are distinctly pitted (Figure 25). The arrangement, size, and shape of these pits are often species-dependent and are thus valuable in wood identification efforts (2). However, hardwood pits are not an open route for rapid intercellular transport (Figure 20) consequently, there is a need for vessel element perforations as a more effective route for fluid translocation. 

Perforations, The open areas at the ends of vessel elements are called perforation plates. The form of these end-wall regions varies between species and sometimes between earlywood and late-... 

Figure 25. SEM of vessel pitting in hardwoods. (A) Vessel vessel pitting (VP) and vessel ray parenchyma pitting (RP) as seen from a transverse radial perspective in cottonwood (F = fibers). (B) Individual vessel element of cottonwood isolated by chemical pulping. (C) Isolated earlywood vessel element of white oak (FP = fiber vessel pitting).

Warts, The presence of a vessel element warty layer is species-dependent, and where it is found, it tends to be associated more with the occurrence of scalariform-type perforation plates (J, 23). As in the case of fibers, vessel warts have no obvious role at the cellular... 

Figure 26. SEM of major types of perforation plates in hardwood vessel elements. (A) Wood radial section of redgum showing scalariform (ladderlike) verjoration plates in three vessel elements (RP = ray cross-field pits). (B) Portion of a maple vessel element containing a simple perforation plate chemically pulped wood. (C and D) Portions oj vessel elements from yellow poplar (C) and paper birch (D) showing scalariform plates with very few bars and with numerous bars chemically pulped wood.

Figure 1.23. A simple perforation plate Figure 1.24. A sealariform perforation plate between vessel elements in Beilschmiedia between two vessel elements in Griselinia tawa. X 450. lucida. x 240.

Figure 1.25. Inter-vessel bordered pits between two adjacent vessel elements in Populus sp. X 500.

Axial parenchyma cells (also called longitudinal parenchyma) are generally very abundant in hardwoods. Like vessel elements and fibres, axial parenchyma cells are derived from the axially-elongated fusiform initials of the vascular cambium but, whereas vessel elements and fibres (except septate fibres) remain unsegmented, axial parenchyma cells are formed by the transverse segmentation of the derivatives of fusiform initials. Axial parenchyma cells, therefore, tend to lie in vertical files... 

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