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Tracheid and Vessel both are parts of xylem tissue. Both of them help in the conduction of water and provide structural support to the trees. Secondary litigation is present and both are tubular. Before looking at the differences between Tracheid and Vessel elements. Let us take a look at the tracheid element and vessel element separately to get a clear understanding of the basics.
Tracheid elements
A tracheid is an elongated and cone-shaped cell present in the xylem of vascular plants. They carry water and mineral salts through the xylem and provide structural support for the plant. Tracheids have pits on the cell walls, allowing them to transfer water between the cells. They do not have a protoplast and are dead at functional maturity.
There are two tracheary elements, one is the tracheid element, and the other is the vessel element. Tracheids are single-celled and their full capacity is limited.
Tracheids are only present in vascular plants allowing them to distinguish between non-vascular plants. Tracheids exhibit two primary functions: they provide structural support to the trees and contribute to the transportation system between the cells.
Vessel elements
Vessel elements are the types of cells present in the water-conducting part of plants called xylem. These xylems conduct water against gravity towards the leaf while phloem conducts the synthesised food using photosynthesis to roots. These are the elements present in angiosperm but absent in gymnosperm. These vessels make angiosperm, hard in nature and gymnosperm is soft
There are two types of cells present in the xylem, they are tracheids and vessel elements. These vessel elements are the major part and this forms an efficient water conduit from roots to leaf. In the secondary xylem, which is formed by the secondary formation in the stem as the stem thickens, this xylem has a vessel element that is formed from the highly vascular cambium.
There is a long cell that divides when vessel elements grow called fusiform cells. These cells are unique and have increased lignin deposition through lignification. These cells have pits as same as tracheid cells but vessel elements have a special feature of conducting water through both ends through a special channel known as perforation plates.
These perforations can be of different shapes including simple perforation or scalariform (ladder type) perforation. Other types include reticulated (net pattern) and foraminate (multiple round opening) perforations. These cells after death still continue their function through lignification.
At the very first, scientists thought their presence in angiosperms and absence in basic plants made them make a conclusion that these are evolutionary modifications. This point was soon found as a misnomer as some angiosperms lack vessel element while some gymnosperm possessed vessel element. In some basic plants, vessel elements like cells are found especially in equisetum as the form of horsetail, in selaginella as spine mosses, and also seen in Marseille, Regnellidium, and Pteridium aquilinum.
Differences between tracheid and vessels
|
Tracheid element |
Vessel element |
|
They are found in all vascular plants and gyro sperms. |
They are found only in angiosperms |
|
It is originated from a single cell |
It originated from a long file of cells and formed a tube-like structure. |
|
It helps in the transfer of water and mineral salt through the mechanical support available in the plant. |
It helps in the conduction of water from the root to other parts of the plant, through mechanical support. |
|
It is an imperforate cell |
It is a perforated cell. |
|
It has a thin cell wall |
It has a thick cell wall |
|
It is inefficient in the conduction of water because of the lack of perforations. |
It is efficient in the conduction of water because of perforated cells. |
|
It contains polygonal cross-sections |
It contains circular cross-sections. |
|
It has a high surface/ volume ratio |
It has a low surface/ volume ratio. |
Conclusion
Tracheid and vessel elements both are responsible for the transportation and circulation of water throughout the plant. They both are called tracheary elements. Secondary lignification is present in both elements. The vessel plays an important role in transporting water from the root to the leaves, whereas the tracheid carries the water and minerals along the path and provides structural support.
