Elements of Phloem Tissue - QS Study
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Phloem tissue is the kind of tissue, made of some living and dead cells which has the chief function to conduct prepared food materials from leaf to different parts of the plant body is called phloem tissue.

The phloem tissue consists of the following four elements:

(i ) Sieve tubes

(ii) Companion cells

(iii) Phloem parenchyma and

(iv) Phloem Sclerenchyma

Sieve tubes: They represent the most active food conducting elements in the phloem tissue. Each sieve tube is formed by a series of hollow, cylindrical cells called sieve tube cells arranged one above the other.

  • These are elongated cells with thin cellulose walls placed end to end which combinedly form a tube
  • The partition walls between the tubes are perforated and are known sieve plates.
  • When matured, the cells have signified wall, a thin layer of protoplasm at the periphery and no nucleus.

Companion cells: They are more or less spindle shaped cells associated with the sieve tube cells. Each companion cell is found attached to any one lateral surface of a sieve cell.

  • The living elongated and marrow cells that he adjacent to sieve is known as comment cells
  • Their cell walls are thin and porous. They make a connection with sieve tubes through the pores.
  • They have dense cytoplasm and large nucleus.

Phloem parenchyma: They are represented by a group of living parenchyma cells that are found in-between the sieve tubes. They are meant only for storage of organic food.

  • They are the simple parenchyma cells present to phloem tissue
  • They are living cells in which the cell walls are thick and composed of cellulose.
  • They have dense cytoplasm and large nucleus.

Phloem sclerenchyma: These fibres are represented by the dead sclerenchyma fibres that are found in between the sieve tubes. They are meant only for providing mechanical support.

  • The sclerenchyma fibre that is present in phloem tissue is called Phloem sclerenchyma. It is also known as blast fibre.
  • These cells are dead but they are very long. Example; Jute fibre.
  • Phloem fibres arise during secondary growth.