Study Guides/Biology/Constituents of Phloem
Study Guide · Biology

What are the Constituents of Phloem?

Phloem is the vascular tissue in plants that transports food (sugars made in leaves) downward to all parts of the plant. In Class 9 Biology (Tissues chapter), knowing its components is essential.

Question (Click to Flip)

What are the constituents of phloem?

Answer

Phloem consists of four components: 1) Sieve Tubes (main conducting cells), 2) Companion Cells (control sieve tubes), 3) Phloem Parenchyma (food storage), and 4) Phloem Fibres (mechanical support).

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Key Facts

Phloem transports food (sugar/sucrose) made in leaves to all plant parts.

4 components: Sieve Tubes, Companion Cells, Phloem Parenchyma, Phloem Fibres.

Key difference from Xylem: Phloem is living (except fibres); Xylem is mostly dead.

Four Constituents of Phloem

Phloem is made up of four types of cells:

1. Sieve Tubes (Sieve Elements)

  • The main conducting cells of phloem.
  • Long, tube-like cells with porous end walls called sieve plates (which have holes to allow sap to flow).
  • They are living cells but lack a nucleus at maturity.

2. Companion Cells

  • Small cells lying alongside each sieve tube cell.
  • They have a nucleus and control the activities of the nuclei-lacking sieve tube cells.
  • They assist in loading and unloading of sugars into sieve tubes.

3. Phloem Parenchyma

  • Living cells that store food and help in lateral conduction of food.
  • Found in dicots; absent in most monocots.

4. Phloem Fibres (Bast Fibres)

  • Dead, thick-walled cells that provide mechanical support to phloem tissue.
  • Commercial fibres like Jute are phloem fibres.

Questions and Answers

What are the constituents of phloem?+

Phloem consists of four components: 1) Sieve Tubes (main conducting cells), 2) Companion Cells (control sieve tubes), 3) Phloem Parenchyma (food storage), and 4) Phloem Fibres (mechanical support).

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