QS Study

Complex tissue is composed of more than one kind of cells. They are two types, namely Xylem tissue and Phloem tissue.

Xylem Tissue

Xylem tissue consists of four types of cells, namely: Tracheids, Vessels or Trachea, Xylem fibre and Xylem Parenchyma.

  1. Tracheids:

Cells are dead, long with transverse ends, containing large vacuole. Cell walls are hard, strong. and lignified. Their main functions are to give mechanical strength and to supply water and dissolved minerals from root to the leaves.

  1. Vessels or Trachea:

Cells are broad and short, placed end to end to form a continuous hollow tube. Water and water dissolved minerals are conducted from root to leaf by these cells.

  1. Xylem fibre:

These are sclerenchymatous cells. Their main function is to give mechanical strength to the plant.

  1. Xylem parenchyma:

These are parenchymatous cells. Functions of these cells are storage and conduction of food materials.

 

Functions of Xylem Tissue

Their functions are to give mechanical strength to the plant body, conduction of water, minerals and food materials and storage of food.

 

Phloem Tissue

Phloem tissue consists of four types of cells, namely: sieve tubes, companion cells, phloem fibres and phloem parenchyma.

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  1. Sieve tube

These are elongate hollow cells placed end-to-end forming.

The partition walls between two adjacent sieve cells are perforated and known as sieve plate. In mature sieve tube, there is no nucleus in the cell. Conduction of food, prepared in the leaves is its main function.

  1. Companion cells

These are parenchymatous, narrow, elongated cells, and are closely associated with the sieve tube. They have dense cytoplasm and a large nucleus. Conduction with the sieve tube is done through the pores present on the walls of these cells. They help the sieve tubes in the conduction of food materials.

  1. Phloem fibre

These are Sclerenchymatous cells. They are also known as bast fibre. Its function is to give mechanical strength.

  1. Phloem parenchyma

These are parenchymatous cells. They help in storage and conduction of food materials.

 

Function of Phloem Tissue

  • There main function is to conduct food materials, prepared in the leaves, to different parts of the plant.
  • They give mechanical strength to plant organ.
  • In case of necessity they store food materials.