The Bio Brief

Do Plants Have a Nervous System?

 No.
Plants do not have:

• Nervous system
• Muscles

Yet, plants can still respond to stimuli like:

• Touch
• Light
• Gravity
• Water

This ability is called coordination in plants.

How Do Plants Respond to Stimuli?

Plants respond using:

• Changes in cell shape
• Growth
• Chemical signals (plant hormones)

Example 1: Touch-me-not Plant (Mimosa)

• When we touch its leaves, they fold and droop.
• This movement is:
  • Very fast
  • Not due to growth
  • Temporary

Flow Chart:

Touch (stimulus)
⬇
Signal in plant cells
⬇
Change in cell shape
⬇
Leaves fold

 This movement happens without growth.

Example 2: Germinating Seed

• When a seed germinates:
  • Root grows downward (towards gravity)
  • Shoot grows upward (towards light)

This movement is:

• Slow
• Permanent
• Due to growth

Flow Chart:

Seed germinates
⬇
Unequal growth in plant parts
⬇
Root down, shoot up

 If growth is stopped, this movement does not occur.

Types of Movements in Plants

Plants show two types of movements:

1. Movement Independent of Growth

• Fast
• Reversible
• No increase in size

Example:
Folding of Mimosa leaves on touch

2. Movement Dependent on Growth

• Slow
• Permanent
• Caused by growth

Example:
Bending of stem towards light
Growth of root towards water

Simple Comparison Table

Movement without Growth	Movement with Growth
Fast	Slow
Temporary	Permanent
No growth involved	Growth involved
Mimosa leaf movement	Seedling growth

Simple Diagrams (Text Form)

Mimosa Plant:

Touch

 ↓

Cell change

 ↓

Leaves fold

Seedling Growth:

Seed

 ↓

Root → Down

Shoot → Up

Key Points to Remember

• Plants do not have nerves or muscles
• They still respond to stimuli
• Some movements are quick (no growth)
• Some movements are slow (growth-based)