Describe gravitropism as directional plant growth
Define the response in terms of growth relative to gravity.
Core and Extended; Biology 0610, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked
Before you begin
- Identify the root and shoot of a seedling; recall growth, cell structure and the variables in a controlled investigation.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What changes in a tropic response?
What you will learn
- Identify gravity as the directional stimulus
- Distinguish new growth from a plant being moved
Describe gravitropism as directional plant growth
| Feature | Meaning |
|---|---|
| Stimulus | Gravity |
| Response | Directional growth of a plant part |
| Positive | Towards gravity |
| Negative | Away from gravity |
Identify gravity as the directional stimulus
Gravitropism is a growth response of a plant part towards or away from gravity. The stimulus has a direction, and the response changes the direction of growth. A root or shoot need not move as a whole organism: a growing region can curve while the seed remains in place. A complete description names gravity and growth, rather than simply saying that a plant moves.
Positive gravitropism means growth towards gravity, usually downwards in a stationary classroom setup. Negative gravitropism means growth away from gravity, usually upwards in that setup. Positive and negative describe direction relative to the stimulus; they do not mean healthy and unhealthy, or faster and slower. Always identify the direction of gravity in the supplied diagram first.
Distinguish new growth from a plant being moved
A seedling placed horizontally can develop a curved growing region over time. A photograph taken immediately after moving its container shows its starting orientation, not necessarily a growth response. Compare the later growing tip with the original axis while keeping the container fixed. Marking the initial outline or using timed photographs helps separate a developing curve from accidental movement.
A fallen pot, a heavy stem sagging or a whole plant being lifted is not by itself evidence of gravitropism. The required response is directional growth. An investigation should allow time for growth, hold other directional influences steady and record both the initial and later orientation. In this Core lesson describe the visible response; the chemical explanation of shoot growth is added in the Supplement sequence.
Pause and explain
Which observation supports gravitropism?
Worked example
A growing root curves down after a horizontal start. Name the response.
Show the worked solution
- Gravity is directed downwards.
- The new root growth is towards gravity.
Answer The root shows positive gravitropism: growth towards gravity.
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Define gravitropism.
Give me a hint
Name both growth and the stimulus.
Compare my reasoning
- A plant part grows in response to gravity.
- The growth can be towards or away from gravity.
Gravitropism is a response in which a plant part grows towards or away from gravity.
Look for these in your work
- Include plant growth
- Specify towards or away from gravity
Distinguish positive and negative gravitropism in a diagram with gravity directed downwards.
Give me a hint
Positive and negative name the relation to the stimulus.
Compare my reasoning
- Towards gravity is positive.
- Away from gravity is negative.
Growth downwards towards gravity is positive gravitropism; growth upwards away from gravity is negative gravitropism.
Look for these in your work
- Give both directions
- Relate each to gravity
A pot is tipped sideways and photographed immediately. Why does that photograph alone not demonstrate gravitropism?
Give me a hint
Look for evidence of growth after the change.
Compare my reasoning
- The photograph only shows repositioning.
- Later directional growth must be observed with the container fixed.
Repositioning alone is not a growth response. Compare later growth with the fixed starting orientation to demonstrate a gravitropic response.
Look for these in your work
- Separate repositioning from growth
- Require a time comparison
Common mistakes
- Using movement alone without growth.
- Calling negative gravitropism harmful growth.
What can you explain now?
Which observation supports gravitropism?
Compare with the explanation
A growing region curves relative to gravity over time
It connects growth with the directional stimulus.
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Make it stick
Define gravitropism and explain why a falling pot is not the required growth response.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.