Summary
Tropic responses are plant growth movements towards or away from stimuli like light and gravity. Gravitropism — a response where parts of a plant grow towards or away from gravity.
Example: Roots exhibit positive gravitropism by growing downwards.
Phototropism — a response where parts of a plant grow towards or away from light.
Example: Shoots exhibit positive phototropism by growing towards light.
Auxin — a plant hormone that controls growth direction by stimulating cell elongation.
Example: Auxin accumulates on the shaded side of a shoot, causing it to bend towards light.
Exam Tips
Key Definitions to Remember
- Gravitropism: Growth response to gravity
- Phototropism: Growth response to light
- Auxin: Plant hormone controlling growth
Common Confusions
- Confusing positive and negative tropisms
- Misunderstanding auxin's role in roots versus shoots
Typical Exam Questions
- What is phototropism? Growth response of plants towards light
- How does auxin affect shoot growth? Auxin stimulates cell elongation on the shaded side, causing bending towards light
- What is the role of auxin in roots? Auxin inhibits cell elongation on the lower side, causing roots to bend downwards
What Examiners Usually Test
- Understanding of positive and negative tropic responses
- The role of auxin in plant growth and development