Difference Between Tracheids and Vessels

Tracheids are highly specialized non-living cells that are present in the xylem of plants. These elements help in water conduction and provide mechanical support to the plants. They are not perforated and are found in seedless vascular plants and gymnosperms such as cedar, pine, ferns, mosses, etc. These are present in the form of a single elongated cell with pointed ends and thickened cell wall. Another element of xylem is phloem that also helps in conduction more efficiently than tracheids as these have perforated in nature.

Tracheids can be seen in angiosperm xylem. They function as conductors. Gymnosperms and ferns also contain them. Tracheid cells are characterised by their pointed ends. On thickening of the secondary cell wall, the tracheids become strongly lignified and die. Tracheids also help the plants with mechanical support. Due to the large surface area to volume ratio, they can also hold water against gravity.

Angiosperms are the only plants that have vessels. They aid in the transport of water and minerals in plants. Dead and tubular cells are created after secondary cell wall thickening and lignification. When these vessels reach maturity, they are devoid of protoplasm.

The Difference is that the Tracheids-

• Tracheids contain thin cell walls.

• Tracheids are the smallest cells in the body (about 1 mm long).

• Because tracheids are imperforated cells, they are inefficient at transferring water.

• Tracheids contain polygonal cross-sections.

• Tracheids contain tapering end walls.

• Tracheids are laterally connected.

• Tracheids consist of a high surface-to-volume ratio.

• Their high adhesive force in the tight tube, tracheids prevent air embolism.

While the Vessels: 

• Vessels are elongated dead cells present in blooming plants' xylem, with punctured cell walls through which water flows.

• Angiosperms are the only plants that have vessels.

• A longitudinal file of cells gives rise to vessels. As a result, they create continuous tubes.

• Vessels have a large lumen.

• A considerable number of tiny pits can be seen in vessels.

• Perforated cells make up vessels.

• Conduction Efficiency of Water

• Water conduction is efficient in vessels.

• The cell walls of vessels have thickened significantly.

• Circular cross-sections are found in vessels.

• Longer cells make up vessels (about 10 cm long).

• Vessels have end walls that are diagonal or transverse.

• End-to-end connections are used to join vessels.

• Vessels have a small surface-to-volume ratio.

• The air embolism is not prevented by vessels.

Tracheids are the most basic cell type in the xylem. They are elongated tube-like cells with tapering ends and have a chisel-like appearance. The cells are no longer active when they reach maturity, and they are bereft of protoplast. The cells are angular and polygonal in cross-section, and the secondary cell wall is extensively lignified. On average, the tracheid is 5–6 mm long.

Pits perforate a considerable section of the tracheid cell wall. They also have pit pairs between two neighbouring tracheids on their shared walls. Pits might be simple circular pits or complicated bordered pits.

Tracheids are the only xylem element seen in Pteridophytes. Tracheids make up the majority of Gymnosperm secondary xylem. In Angiosperms, tracheids coexist with other xylem components. Certain early Angiosperms, such as Drimys, Trochodendron, and Tetracentron, have only tracheids in their xylem (vessels absent).

A lengthy tube-like structure made up of a sequence of cells arranged end to end makes up the vascular system. Each cell is referred to as a "vessel member" or "vessel element." Water and minerals can readily move between the cells thanks to perforations (large apertures) in the end walls of each vessel part. Typically, vessel members are shorter than tracheids. Vessels, on the other hand, are substantially larger than tracheids in diameter. This allows water to flow through the vessel lumen more rapidly and efficiently.

Advanced vascular cells have a shorter length and a larger diameter, and they have a drum-like form (as in Quercus alba). The terminal wall of either vascular member is oblique or transverse. Vessels with oblique ends are thought to be primitive, whereas those with transverse ends are thought to be advanced. A tail-like tip extends beyond the terminal wall in some species, such as Malus. The apertures or pores in the end wall of each vessel are known as perforations (Perforation plate: the region of the vessel with perforation occurs). Perforations on the end wall are the most common, however, lateral perforations can also occur.

The Highlights are-

• The endplates of vessels have holes, whereas the endplates of tracheids do not.

• Tracheids are made up of single cells, whereas vessels are made up of a group of cells.

• Tracheids can be found in all vascular plants, but vessels are only seen in angiosperms.

• Tracheids are small and narrow, whereas vessel components are large and wide.

• When compared to vessel elements, tracheids have a substantially higher surface-to-volume ratio.

• Vessels are larger than the tracheids they are connected to.

• The perforated plate has a distinct morphology than tracheids.

• The vessel components of angiosperms are shorter than the tracheids.

• In comparison to arteries, tracheids are considered primitive cells.

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