Difference Between Vessel Elements and Tracheids
Vessel Elements vs Tracheids
Higher plants have evolved a well developed transportation system for the conduction of water. They have specialized some of the cells to help in the ascent of sap. These are the vessel elements and tracheids which are responsible for the transportation and circulation of water within the plant body. Together they are called tracheary elements. Tracheary elements, xylem fibers, and xylem parenchyma are closely associated to form xylem tissues. Xylem altogether forms the total translocation system in higher plants. Evolution of this tissue is considered to be the root cause of success of the angiosperms.
Tracheary elements, both tracheids and vessels, are highly specialized cells. These cells are devoid of protoplast when mature. These non-living cells are elongated with lignified cell walls. The main difference between tracheids and vessels is that vessels have perforations at the end plates which make them a tube-like, long structure while tracheids do not have end plates.
Vessel elements are the building blocks of the water transportation system of the plants. They are responsible for the ascent of sap from roots to leaves and the tip of the plants. These are lignified cells which are surrounded by parenchymal cells. These cells vary in length. The vessel members originate from longitudinal stacks of cells. All the vessels are connected to each other at ends through perforated, tube-like structures. The perforations or the perforated plates may also vary in shape.
According to their shapes, they are named as simple perforations when simple; scalariform perforations when they are ladder like; foraminate perforation plates when several round openings are there; reticulate perforation plates when a net-like pattern with many openings is there. The sap moves from one vessel member to other through these perforations.
Xylem vessels give an overall strength to the plant body. They are present in angiosperms only.
Tracheids are the elongated cells of the xylem. They also lack protoplasm like the vessels. They are similar to vessels except for a few facts. Tracheids originate from individual cells. These cells are imperforate and have only pit pairs on the common walls. A tracheid’s build varies by location. Tracheids are present in all vascular plants.
Vessels have perforations at the end plates while tracheids do not have end plates.
Tracheids are derived from single individual cells while vessels are derived from a pile of cells.
Tracheids are present in all vascular plants whereas vessels are confined to angiosperms.
Tracheids are thin whereas vessel elements are wide.
Tracheids have a much higher surface-to-volume ratio as compared to vessel elements.
Vessels are broader than tracheids with which they are associated.
Morphology of the perforation plate is different from that in tracheids.
In angiosperms, vessel elements are shorter than the tracheids.
Tracheids are considered to be primitive cells as compared to vessels.
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