The Bio Brief

Can Plants Respond Immediately?

 Yes.
Some plants show quick responses even though they:

• Do not have a nervous system
• Do not have muscles

Example:

• Touch-me-not (Mimosa) plant folds its leaves when touched.

How Do Plants Detect Touch?

• When the plant is touched, cells at the touched part detect the stimulus.
• The movement, however, happens at a different part of the plant.
• So, the information about touch must be passed from cell to cell.

How Is Information Transmitted in Plants?

• Plants use electrical-chemical signals to send information.
• Unlike animals:
  • Plants do not have nerves
  • There is no specialised tissue for conduction
• The signal spreads slowly from one cell to another.

How Do Plant Leaves Move Without Muscles?

Key Idea:

Plant cells change shape to cause movement.

How does this happen?

• Plant cells control the amount of water inside them.
• When water enters:
  • Cells swell
• When water leaves:
  • Cells shrink

This swelling and shrinking causes the leaf to fold or droop.

Flow Chart: Touch-me-not Plant Movement

Touch (stimulus)
⬇
Cells detect touch
⬇
Electrical-chemical signal spreads
⬇
Water moves in/out of cells
⬇
Cells change shape
⬇
Leaves fold

Simple Diagram (Text Form)

Touch

 ↓

Signal in cells

 ↓

Water movement

 ↓

Cell shape change

 ↓

Leaf movement

Comparison with Animals

Animals	Plants
Have nerves	No nerves
Have muscles	No muscles
Use muscle proteins	Use water movement
Fast responses	Comparatively slower

Key Points to Remember

• Immediate plant movements do not involve growth
• Plants use electrical-chemical signals
• Movement happens due to change in water content of cells
• Example: Mimosa leaf folding