Supporting Tissues in Plants – SS2 Biology Lesson Note (First Term)

Supporting tissues are groups of plant cells that give a plant its definite shape, strength and rigidity, and help it resist external forces such as wind and water. The five types are parenchyma, collenchyma, sclerenchyma, xylem and phloem. Each type has its own cell structure and function.

Behavioural objectives

By the end of the lesson, students should be able to:

• State why plants need supporting tissues.
• List the five types of supporting tissues in plants.
• Describe the cell structure of each type.
• State the functions of each type.

Why do plants need supporting tissues?

Plants need supporting tissues for:

1. Definite shape
2. Strength
3. Rigidity
4. Resistance against external forces such as wind and water

What are the types of supporting tissues?

1. Parenchyma tissues
2. Collenchyma tissues
3. Sclerenchyma tissues
4. Xylem tissues
5. Phloem tissues

Parenchyma tissues

Parenchyma tissues are made up of living cells with cellulose and many air spaces within them. This is the most common and abundant plant tissue.

Functions

1. It gives firmness and turgidity to the stems of the hibiscus.
2. It stores food and water.
3. It takes part in food synthesis in leaf mesophyll.

Collenchyma tissues

Collenchyma tissues are made up of living cells which are elongated and thickened at the corners.

Functions

• It provides strength and support in young growing plants.
• It gives flexibility and resilience to the plant.

Sclerenchyma tissues

Sclerenchyma tissues are made up of thick cells containing cellulose and lignin. The tissues are rich in fibres.

Functions

1. It gives flexibility to plants.
2. It provides strength, rigidity, hardness and support to plants.

Xylem tissues

Xylem tissues are found in the vascular tissues of stems, roots and leaves.

Functions

1. It provides support, strength and shape to the plant.
2. It helps to conduct water and mineral salts from the roots to the leaves.

Phloem tissues

Phloem tissues are also located in the vascular bundles of all plants, in their roots, stems and leaves.

Functions

1. It conducts manufactured food from the site of production to the site of consumption and storage.
2. It assists in providing support to the entire plant.

Evaluation

1. State four reasons why plants need supporting tissues.
2. List the five types of supporting tissues in plants.
3. Describe the cells of collenchyma tissue.
4. State two functions of xylem tissues.
5. Which plant tissue is the most common and abundant?

Assignment

1. Name the two supporting tissues found in the vascular bundles and state one function of each.
2. State two differences between the cells of parenchyma and sclerenchyma tissues.