Vascular Tissue System: Vascular tissues are groups of tissues that transport or conduct the passage of fluid and nutrients. They are arranged in such a way that the passage of transporting materials can be transported easily. The cells in vascular tissues are typically long and slender. Vascular tissue is made up of more than one cell type, found in most of the vascular plants.
The vascular tissue system consists primarily of two types of cells which are xylem and phloem. Both the cells are responsible for the conduction of water, minerals and nutrients throughout the plant. Xylem cells help to transport water and nutrients from roots to stem and are long cells, consisting of two other types of cells known as parenchyma and fibres. Phloem is responsible for transporting sugars and other organic molecules.
Vascular tissues are arranged in the form of long distinct strands which are known as vascular bundles. In addition to the xylem and phloem, the vascular bundles also include other supporting and protecting cells. In between the xylem and phloem, there exists a meristem which is known as vascular cambium.
Features of Vascular Tissue System
- Xylem is one of the conducting tissues that is responsible for the transport of nutrients and water from roots to the aerial parts of the plant such as stem and leaves.
- It is made up of specialised water-conducting cells that are known as tracheary elements.
- The first tracheary element found in xylem is tracheids. It is long and tapered and also lignified. Its primary function is to transport water and give structural support to the plants.
- Some gymnosperms and other seedless plants sometimes only consist of tracheids as their water conducting element.
- The second tracheary element found in xylem are vessel members. They are more specialised cells than the tracheids.
- Also known as vessel element, it is the primary element responsible for the transport of water in angiosperms despite the presence of tracheids. It is not found in gymnosperms.
- Apart from the tracheary elements, the xylem also consists of fibre cells and parenchyma tissue.
- The fibre cells are lignified and provide structural support to the plants. Parenchyma on the other hand are unspecialised and thin walled cells that are used for storage purposes.
- Phloem is another conducting vascular tissue found in plants that transports food made in leaves during photosynthesis to all the parts of the plant.
- The phloem is composed of three types of cells – the conducting cells, the parenchyma cells and the supportive cells.
- The conducting cells, also called sieve elements, are composed of columns of sieve tube cells that have perforations in their lateral walls and that helps in the conduction of food throughout the plant.
- The parenchyma consists of unspecialised cells used for storage and two specialised cells namely – companion cells and albuminous cells.
- The companion cells, as the name suggests are the companion of the sieve tube cells that help in carrying out the metabolic functioning of the sieve elements.
- The companion cells are connected with the sieve tube elements by plasmodesmata.
- The albuminous cells are analogous to companion cells that are only found in non-flowering vascular plants.
- The supportive cells are sclerenchymatous cells, namely, fibres and sclereids.
- Both the cells have secondary cell walls that make them rigid and give them a high tensile strength. They are mainly present for mechanical and supportive functions.
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By Team Learning Mantras