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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