tracheid

Examples of tracheid in the following topics:

• Vascular Tissue: Xylem and Phloem

  • The tissue consists of vessel elements, conducting cells, known as tracheids, and supportive filler tissue, called parenchyma .
  • Vessels and tracheids are dead at maturity.
  • Tracheids have thick secondary cell walls and are tapered at the ends.
  • It is the thick walls of the tracheids that provide support for the plant and allow it to achieve impressive heights.
  • Tracheids (top) and vessel elements (bottom) are the water conducting cells of xylem tissue.

• Stem Anatomy

  • Xylem tissue has three types of cells: xylem parenchyma, tracheids, and vessel elements.
  • Tracheids are xylem cells with thick secondary cell walls that are lignified.
  • Water moves from one tracheid to another through regions on the side walls known as pits where secondary walls are absent.
  • Vessel elements are xylem cells with thinner walls; they are shorter than tracheids.

• Bryophytes

  • They generally lack lignin and do not have actual tracheids (xylem cells specialized for water conduction).

• Primary and Secondary Growth in Stems

  • The cells of the vascular cambium divide and form secondary xylem (tracheids and vessel elements) to the inside and secondary phloem (sieve elements and companion cells) to the outside.
  • This alternation of early and late wood is due largely to a seasonal decrease in the number of vessel elements and a seasonal increase in the number of tracheids.

• Movement of Water and Minerals in the Xylem

  • At night, when stomata close and transpiration stops, the water is held in the stem and leaf by the cohesion of water molecules to each other as well as the adhesion of water to the cell walls of the xylem vessels and tracheids.
  • The xylem vessels and tracheids are structurally adapted to cope with large changes in pressure.

• Diversity of Gymnosperms

  • The wood of conifers is more primitive than the wood of angiosperms; it contains tracheids, but no vessel elements, and is, therefore, referred to as "soft wood."

• Plant Tissues and Organ Systems

  • It includes three different cell types: vessel elements and tracheids (both of which conduct water) and xylem parenchyma.

• Leaf Structure, Function, and Adaptation

  • The xylem consists of tracheids and vessels, which transport water and minerals to the leaves.