Explain All Things About Tissue (Plant & Animals) Minimum Pages = 5 With Pictures
Answers
Plant tissues are of two main types, viz. meristematic tissue and permanent tissue.
1 - Meristematic Tissue:-Plant tissues in which cells keep on dividing are called meristematic tissue. Meristematic tissues are present in those parts of plants which keep on growing. Meristematic tissues are classified on the basis of their location. They are of following types:
Apical Meristem:- Apical meristem is present on root apex, stem apex, leaf buds and flower buds. They are responsible for growth in length, i.e. primary growth.Lateral Meristem: Lateral meristem is present along the side of the stem. They are responsible for growth in girth, i.e. secondary growth.
Intercalary Meristem: Intercalary meristem is present at the base of leaf or internodes. They are present on either side of the node.
Since cells of meristematic tissue are highly active so they have dense cytoplasm. Vacuole is absent in these cells.
2 - Permanent Tissue:Once the cells of meristematic tissue divide to a certain extent, they become specialized for a particular function. Permanent tissues are of two types, simple permanent tissue and complex permanent tissue.
(a) Simple Permanent Tissue: Simple permanent tissue is composed of similar types of cells. Simple permanent tissues are of three types, viz. parenchyma, collenchyma and sclerenchyma.
(1) Parenchyma:
The cells of parenchyma have thin cell wall. They are loosely packed;
with lot of intercellular spaces between them. Parenchyma makes the
largest portion of a plant body. Parenchyma mainly works are packing
material in plant parts. The main function of parenchyma is to provide
support and to store food.
(2) Collenchyma: The cell wall of collenchyma is thickened at corners. Intercellular spaces are very few. Collenchymas provides some degree of structural rigidity with flexibility.
(3) Sclerenchyma:
The cell wall in sclerenchyma is highly thickened all around. The cells
are dead and intercellular space is absent.
Complex permanent tissue is composed of different types of cells. Complex permanent tissues are of two types, viz. xylem and phloem. Xylem and phloem together make the vascular bundle in plants.
Xylem: Xylem is composed of trachieds, vessels, xylem parenchyma and xylem fibres. The cells of xylem are dead; except the cells of xylem parenchyma. Trachieds and vessels are tubular structures and thus they provide a channel for conduction of water and minerals. Xylem fibre provides structural support to the tissue. Xylem parenchyma stores food. Phloem: Phloem is composed of sieve tubes, companion cells, phloem fibre and phloem parenchyma. Sieve tubes are tubular cells with perforated walls. Sieve tubes are the conducting elements of phloem. Phloem is responsible for translocation of food in plants. The transport of food in phloem is a two way movement.