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An elongate, spindle-shaped xylem cell, lacking protoplasm at maturity, and having secondary walls laid in various thicknesses and patterns over the primary wall.



a dead lignified plant cell that functions in water conduction. Tracheids are found in the xylem of all higher plants except certain angiosperms, such as cereals and sedges, in which the water-conducting function is performed by vessels, or tracheae. Tracheids are usually polygonal in cross section; their walls have annular, spiral, or scalene thickenings or rimmed pores. The cells range in length from fractions of a millimeter to 3–5 mm (pine, larch) and even 10 mm (agave). In the process of evolution, tracheids developed into fibrous tracheids with limited water-conducting ability and into specialized mechanical elements known as libriform fibers.

References in periodicals archive ?
1] represents the time when capillary rising starts to become significant, even though the simple absorption in surface open-ended tracheids is not yet completed, whereas [t.
After pressure treatment samples were wrapped in parafilm[R] for about 30 min to permit diffusion of air into cavitated tracheids.
Gymnosperm tracheids with torus-margo pit membranes.
What does SEM tell us about vessel elements and tracheids in monocots, and how does that change our concept of what vessel elements are and how they work?
2000) reported that transition from juvenile to mature wood in loblolly pine occurred between the 8th and 12th ring based on density and tracheid length.
They differ from tracheids at functional maturity solely in the dissolution of pit membranes in a number of the bordered pit pairs in their overlapping ends .
Painting or coating of the wood member's lateral sides may also slow the process of air removal from wood tracheids, limiting the rate of liquid penetration.
Reversible deformation of transfusion tracheids in Taxus baccata is associated with a reversible decrease in leaf hydraulic conductance.
Tracheids in the sense of Bailey & Tupper (1918), Bailey (1936), Carlquist (1961, 1988), IAWA Committee on Nomenclature (1964) and Sano et al.
2) At maturity, tracheary elements are emptied of all cell contents to form hollow tubes constituting vessels and tracheids, which serve as a pathway for fluids.