Tracheids are elongated cells in the xylem of vascular plants, serving in the transport of water. The build of tracheids will vary according to where they occur. Cells in culture, stained for keratin (red) and DNA (green). ... It has been suggested that Vessel element be merged into this article or section. ... Divisions Non-seed-bearing plants Equisetophyta Lycopodiophyta Psilotophyta Pteridophyta Superdivision Spermatophyta Pinophyta Cycadophyta Ginkgophyta Gnetophyta Magnoliophyta The vascular plants are plants in the Kingdom Plantae (also called Viridiplantae) that have specialized tissues for conducting water. ...

Tracheids are one of two types of tracheary elements, vessel elements being the other. All tracheary elements will develop a thick lignified cell wall, and at maturity the protoplast has broken down and disappeared. The presence of tracheary elements is the defining characteristic of vascular plants to differentiate them from non-vascular plants. A vessel element is an important part of the wood (Xylem) of hardwood plants and is found in all Angiosperms. ... Initially protoplast (in Greek: proton = first and platho = mould) referred to the first organized body of a species this meaning is similar to the non-biological definition, the first from from which all subsequent forms are derived. ... Divisions Simple nonvascular plants   Green algae Complex nonvascular plants   Bryophyta, mosses   Hepaticophyta, liverworts   Anthocerotophyta, hornworts Non-vascular plants is a name for a group of plants. ...

The two major functions that tracheids may fulfill are

• as part of the transport system
• in structural support

In most cases, the prime function of tracheids is that of transporting water. They occur in vascular bundles throughout the non-woody parts of the vascular plant and provide water and minerals collected by the roots to leaves and other parts of the plant (stem, flowers, fruits etc). Cross section of celery stalk, showing vascular bundles, which include both phloem and xylem. ...

A good example of structural support is in softwoods where tracheids are the major cell type. Tracheids give softwood its strength. Pictures of softwood tracheids in cross section and in maceration; both in pine. Despite being fairly hard, cedar is a softwood Softwood is the wood from conifers. ...

Because tracheids have a much higher surface to volume ratio compared to vessel elements, they serve to hold water against gravity (by adhesion) when transpiration is not occurring. This is likely one mechanism that helps plants prevent air emboli. Dew drops adhering to a spider web Water droplets adhering on a hibiscus petal Adhesion is the molecular attraction exerted between bodies in contact. ... Transpiration is a continuous process caused by the evaporation of water from leaves of plants and its corresponding uptake from roots in the soil. ...

See also

• vessel element
• xylem

A vessel element is an important part of the wood (Xylem) of hardwood plants and is found in all Angiosperms. ... It has been suggested that Vessel element be merged into this article or section. ...

References

• Wilson, K. & D.J.B. White (1986). The Anatomy of Wood: its Diversity and variability. Stobart & Son Ltd, London