Root Systems (Leaving Cert Biology): Revision Notes

Root System

Types of Root Systems

1. Tap roots
2. Fibrous roots
3. Adventitious roots

1. Tap Roots

• Tap roots have a main root called a tap root.
• Lateral roots grow from the main root.
• The tips of the lateral roots have thousands of tiny root hairs for absorption.
• Most dicotyledons (dicots) have tap root systems, e.g., dandelion, ash, carrot, oak.

2. Fibrous Roots

• Fibrous roots consist of many roots that are all the same size.
• Most monocotyledons (monocots) have fibrous root systems, e.g., grasses.

3. Adventitious Roots

• Adventitious roots are roots that grow in unusual or unexpected places.
• Examples include roots at the base of onions and the gripping roots of ivy.

Zones of a Root

Longitudinal Section of a Dicot Root

1. Zone of protection

2. Meristematic zone

3. Zone of elongation

4. Zone of differentiation

   

5. Zone of Protection

• The root cap protects the root tip as it grows through the soil.

5. Meristematic Zone

• A meristem is an area where cell division (mitosis) takes place in a plant.
• Apical meristems are found in the root and shoot tips.
• Other meristems are found at the edges of some plant stems and in leaves and fruit.

6. Zone of Elongation

• When new cells are formed by the meristem, they are very small.
• In the zone of elongation, plant growth regulators (auxins) stimulate the cells to grow longer.

7. Zone of Differentiation

• New cells formed from mitosis are all similar (undifferentiated).
• In the zone of differentiation, cells develop into different types of tissues:
• Dermal tissue: Protects the plant.
• Ground tissue: Found between the dermal and vascular tissues.
• Vascular tissue: Xylem and phloem which transport water, minerals, and food.
• Root hairs are formed here, increasing surface area for water and nutrient absorption.

Plant Tissues in a Root

Transverse Section of a Dicot Root

• Root hair
• Dermal tissue
• Ground tissue
• Vascular tissue
• Xylem
• Phloem

Note: Xylem always forms the 'X' in the vascular tissue.