Define the term Phloem. Explain the types of it.

1.	Define the term Phloem. Explain the types of it.
Answer» Phloem : They also consist of both parenchymatous and schlerenc- -hymatous cells. Phloem consists of four types of element : (i) Sieve tubes : • Sieve tubes are slender tube like structures made up of elongated, thin walled cells placed end to end. • The end walls of sieve tube cells are perforated by numerous pores, called as sieve plates. • Nucleus of sieve cell degenerates at maturity. However, cytoplasm persists, because of protoplasmic continuation of sieve tube with companion cell through plasmodesmata. • Sieve cells possess slime protein or protein which is concerned with growth and repair of sieve cells. (ii) Companion cells : • Companion cells have dense cytoplasm and prominent nuclei. (iii) Phloem fibre : • They give mechanical support to sieve tubes. (iv) Phloem parenchyma : • They store food and help in radial conduction of food.

Answer»

Phloem : They also consist of both parenchymatous and schlerenc- -hymatous cells.

Phloem consists of four types of element :

(i) Sieve tubes :

• Sieve tubes are slender tube like structures made up of elongated, thin walled cells placed end to end.

• The end walls of sieve tube cells are perforated by numerous pores, called as sieve plates.

• Nucleus of sieve cell degenerates at maturity. However, cytoplasm persists, because of protoplasmic continuation of sieve tube with companion cell through plasmodesmata. • Sieve cells possess slime protein or protein which is concerned with growth and repair of sieve cells.

(ii) Companion cells :

• Companion cells have dense cytoplasm and prominent nuclei.

(iii) Phloem fibre :

• They give mechanical support to sieve tubes.

(iv) Phloem parenchyma :

• They store food and help in radial conduction of food.

Discussion

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