Plz tell types of complex tissue with their function
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see complex tissue is a permanent tissue they are specialised cells which perform specific function in body.
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II. Complex Tissues:
The complex tissues are composed of different types of cells performing diverse functions. These are of two types xylem and phloem.
(i) Xylem:
Structurally, xylem consists of both living and nonliving cells. Xylem consist of four elements: tracheids, vessels, xylem fibers and xylem parenchyma.
Tracheids:
Tracheids are elongated or tube-like dead cell with hard, thick and lignified walls. Their ends are tapering, blunt or chisel-like. Their function is conduction of water and providing mechanical support to the plant.
Vessels:
Vessel is long cylindrical, tube like structure with lignified walls and a wide central lumen. The cells are dead as these do not have protoplast. The cells are arranged in longitudinal series in which the partitioned walls (transverse walls) are perforated, so the entire structure looks-like a water pipe. Their main function is transport of water and minerals. It also provides mechanical strength.
Xylem fibers:
These cells are elongated, lignified and pointed at both the ends. A xylem fiber helps in conduction of water and nutrients from root to the leaf and provides mechanical support to the plant.
Xylem Parenchyma:
The cells are living and thin walled. The main function of xylem parenchyma is to store starch and fatty substances.
(ii) Phloem:
Phloem consists of four types of elements – sieve tubes, companion cells, and phloem parenchyma and phloem fibers.
Sieve tube:
These are elongated, tube-like slender cells placed end to end. The transverse walls at the ends are perforated and are known as sieve plates. The main function of sieve tubes is translocation of food, from leaves to the storage organs of the plants.
Companion Cells:
These are elongated cells attached to the lateral wall of the sieve tubes. These are mostly found in angiosperms.
Phloem Parenchyma:
The phloem parenchymas are living cells which have cytoplasm and nucleus. Their function is to store food materials.
Phloem fibers or bast fibers:
Sclerenchymatous cells associated with primary and secondary phloem are commonly called phloem fibers. These cells are elongated, lignified and provide mechanical strength to the plant body.
The complex tissues are composed of different types of cells performing diverse functions. These are of two types xylem and phloem.
(i) Xylem:
Structurally, xylem consists of both living and nonliving cells. Xylem consist of four elements: tracheids, vessels, xylem fibers and xylem parenchyma.
Tracheids:
Tracheids are elongated or tube-like dead cell with hard, thick and lignified walls. Their ends are tapering, blunt or chisel-like. Their function is conduction of water and providing mechanical support to the plant.
Vessels:
Vessel is long cylindrical, tube like structure with lignified walls and a wide central lumen. The cells are dead as these do not have protoplast. The cells are arranged in longitudinal series in which the partitioned walls (transverse walls) are perforated, so the entire structure looks-like a water pipe. Their main function is transport of water and minerals. It also provides mechanical strength.
Xylem fibers:
These cells are elongated, lignified and pointed at both the ends. A xylem fiber helps in conduction of water and nutrients from root to the leaf and provides mechanical support to the plant.
Xylem Parenchyma:
The cells are living and thin walled. The main function of xylem parenchyma is to store starch and fatty substances.
(ii) Phloem:
Phloem consists of four types of elements – sieve tubes, companion cells, and phloem parenchyma and phloem fibers.
Sieve tube:
These are elongated, tube-like slender cells placed end to end. The transverse walls at the ends are perforated and are known as sieve plates. The main function of sieve tubes is translocation of food, from leaves to the storage organs of the plants.
Companion Cells:
These are elongated cells attached to the lateral wall of the sieve tubes. These are mostly found in angiosperms.
Phloem Parenchyma:
The phloem parenchymas are living cells which have cytoplasm and nucleus. Their function is to store food materials.
Phloem fibers or bast fibers:
Sclerenchymatous cells associated with primary and secondary phloem are commonly called phloem fibers. These cells are elongated, lignified and provide mechanical strength to the plant body.
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