Question

briefly explain about complex permanent tissues​

Answer 1

complex permanent tissues

• complex tissues are made up of more than one type of cells.
• all these cells coordinate to perform a common function.
• Xylem and Phloem are examples of complex permanent tissues which are conductive tissues and constitute a vascular bundle. it helps plants to survive in terrestrial environment.

Xylem:-

• it consists of tracheids, vessels, xylem parenchyma and xylem schlerenchyma.
• it is called wood and is the vascular and mechanical tissue.
• it has thick walled cells in form of tabular passage, where most of them are dead cells.
• it has unidirectional movement.

Tracheids:-

• these are elongated angular dead cells involved in the conduction of water and minerals in gymnosperms. (having naked seeds).
• These are single celled and end wall is intact.
• walls are thick with a narrow lumen.

Vessels:-

• these are advanced elements found in angiosperms (flowering plants).
• Vessels are cylindrical tube like structures made up of row of cells placed one above the other by end to end for efficient conduction of water.
• End walls get divided and get perforated.
• Walls are thin and have a wider lumen.

Xylem parenchyma:-

• it consists of living cells.
• it stores food.
• it helps in lateral conduction of water.

Xylem schlerenchyma:-

• it consists of dead cells, with narrow and thick walls containing lignin for mechanical support.
• the annual rings present in trunk of a tree are xylem rings which helps in finding the age of the tree.

Phloem:-

• it is made up of sieve tubes, companion cells, phloem fibres and Phloem parenchyma. it has a bidirectional movement.

Sieve tubes:-

• these are slender tubes like structures made up of elongated, thin walled cells which are placed end to end.
• the end walls are perforated by many pores and are called sieve plates.
• Nucleus of sieve cells degenerates at maturity, but cytoplasm persists.
• it has protein which helps in growth and repair of sieve cells.

Companion cells:-

• They have dense cytoplasm and large elongated nuclei.
• they originate from the same mother cell, therefore, called sister cells.
• it connects to the sieve tube with numerous plasmodesmata (cylindrical, lined by plasma membrane of the adjacent cells).

Phloem Parenchyma:-

• these are thin walled living cells of parenchyma of phloem.
• They store food and helps in radial conduction and slows down lateral conduction.

Phloem fibres (or phloem schlerenchyma)

• it gives mechanical support to sieve tubes.
• these are thick ward, dead cells which have narrow lumens.
• Bast fibres are obtained from jute, hang, flax which has commercial value.
• In phloem, all elements are living except phloem schlerenchyma.

Answer 2

Explanation:

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⠀⠀⠀⠀⠀⠀Complex permanent tissue is defined as a collection of structurally dissimilar cells performing a common function or set of functions. They are made up of more than one type of cells. They are of two types xylem and phloem. Xylem is the chief water conducting tissue of the plants. It functions as a conducting tissue for water and minerals from the roots to the stems and leaves. Phloem is the chief food carrying tissue of the plants. It is a living tissue that carries food materials, from the place it is available to the places where it is needed.

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