Tracheid

A tracheid is an elongated xylem cell that conducts water through pits in its thickened walls. Its tapered ends overlap neighboring cells, and it also helps support the plant.

Xylem: The vascular tissue that transports water and dissolved minerals through plants and provides structural support. Tracheids are one of the two principal water-conducting cell types in xylem.
Secondary cell wall: A rigid wall layer deposited inside a plant cell’s primary wall after cell expansion slows or stops. Tracheids develop thick secondary walls that strengthen the water-conducting pathway.
Vessel: A continuous xylem conduit formed by vessel elements joined end to end. Vessels generally conduct water more efficiently than individual tracheids.
Wood: The secondary xylem produced by woody plants, composed mainly of water-conducting cells and supporting tissues. Tracheids make up most of the wood in conifers and many other plants.
Bordered pit: A specialized opening in a plant cell wall, formed where the secondary wall arches over a pit membrane. Water passes between neighboring tracheids through these wall structures.
Programmed cell death: A genetically regulated process by which cells dismantle themselves and die. Mature tracheids lose their living contents before functioning as conduits.
Sieve tube element: A living phloem cell specialized to transport sugars and other organic substances. It conducts dissolved nutrients, unlike tracheids, which conduct water and minerals.
Softwood: Wood from gymnosperms, typically composed chiefly of tracheids rather than vessels. Its anatomy makes tracheids both the main conduits and structural cells.
Cohesion-tension theory: The theory that water rises through xylem as evaporation creates tension transmitted through cohesive water molecules. The tension it describes pulls water through tracheid networks.
Vascular cambium: A lateral meristem that produces secondary xylem inward and secondary phloem outward. In woody plants, its activity generates much of the tracheid-bearing wood.

Linked from 8 pages