Tracheid

Tracheid of oak shows pits along the walls. It is longer than a vessel element and has no perforation plates.

A tracheid is a long, lignified cell in the xylem of vascular plants. Tracheid first named after the German botanist Carl Gustav Sanio in 1863. Used from German Tracheide. There are often pits (also known as pupils or guide holes) or decoratives on the cell walls of tube cells. When mature, tracheids do not have a protoplast. The main functions are to transport water and inorganic salts, and to provide structural support for trees. In addition, angiosperms use another water transport structure called vessel elements in the xylem , which are smaller than a catheter and do not have a perforation plate; most polypodiopsida are no catheter in the lignin of gymnospermae, only the pipe cells are responsible for the transportation of water. The wood (softwood) of gymnosperms such as pines and gymnospermae is mainly composed of tracheid.

Tracheid may be a single source structure in evolution. The fossil record shows that the tube cells of early plants were S-type, G-type and P-type. The first two of them were lignified and had holes to facilitate the transportation of water between cells. The latter had wall holes similar to the existing plant tubes, and later more complex wall holes appeared, such as bordered pits on many tracheid, which allowed plants to transport water between tubes while reducing the risk of embolization transmission between tracheid.

Further reading

• Wilson, K.; White, D. J. B. (1986). The Anatomy of Wood: Its Diversity and Variability. London: Stobart & Son Ltd. ISBN 0-85442-033-9.

External links

• Pictures of softwood tracheids in cross section and in maceration; both in pine.