Grass seedlings have coleoptiles which respond to light under certain conditions. An experiment was set up in which different parts of coleoptiles were covered by a 'blindfold'. Light could not reach any of the parts covered by a blindfold but could fall on uncovered parts of the coleoptiles. The different treatments were labelled A to G inclusive. a. What is the term used to describe a plant's growth response to light? b. i. In which of the treatments shown would you expect to see a growth response to light? ii. Explain why you would expect to see this response in your choices in part b.i. c. Use diagrams to explain the processes occurring in a plant when a growth response to light occurs.

SSCE VCE Biology Scientific Investigation and Research Methods: Grass seedlings have coleoptiles

Grass seedlings have coleoptiles which respond to light under certain conditions - VCE - SSCE Biology - Question 3 - 2002 - Paper 1

Question 3

Grass seedlings have coleoptiles which respond to light under certain conditions. An experiment was set up in which different parts of coleoptiles were covered by a ... show full transcript

Worked Solution & Example Answer:Grass seedlings have coleoptiles which respond to light under certain conditions - VCE - SSCE Biology - Question 3 - 2002 - Paper 1

Step 1

What is the term used to describe a plant's growth response to light?

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Answer

The term used to describe a plant's growth response to light is phototropism. This process involves the bending of a plant towards the light source as it seeks optimal conditions for photosynthesis.

Step 2

In which of the treatments shown would you expect to see a growth response to light?

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Answer

I would expect to see a growth response in treatments A, E, F, and G. In these treatments, the tip of the coleoptile is exposed to light.

Step 3

Explain why you would expect to see this response in your choices in part b.i.

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Answer

I would expect to see a growth response in A, E, F, and G because in each of these treatments, the tip of the coleoptile is exposed to light. The tips are crucial for detecting light and initiating the growth response. When light is detected, auxin is redistributed to the shaded side, causing the plant to bend towards the light.

Step 4

Use diagrams to explain the processes occurring in a plant when a growth response to light occurs.

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Answer

When a plant experiences light, the following processes occur:

Light Perception: Light is detected by the coleoptile tip. This initiates the phototropic response.
Auxin Redistribution: Auxin, a plant hormone that promotes cell elongation, redistributes towards the shaded side of the coleoptile.
Cell Elongation: The cells on the shaded side elongate more than those on the illuminated side, resulting in the coleoptile bending towards the light source.
Diagram:
- A diagram illustrating a coleoptile bending towards light could show:
  - The direction of light
  - Distribution of auxin
  - Elongated cells on the shaded side
  - Resulting bend towards the light.

The dynamic interaction of these processes leads to the optimal orientation for light absorption.

Grass seedlings have coleoptiles which respond to light under certain conditions - VCE - SSCE Biology - Question 3 - 2002 - Paper 1

Worked Solution & Example Answer:Grass seedlings have coleoptiles which respond to light under certain conditions - VCE - SSCE Biology - Question 3 - 2002 - Paper 1

What is the term used to describe a plant's growth response to light?

In which of the treatments shown would you expect to see a growth response to light?

Explain why you would expect to see this response in your choices in part b.i.

Use diagrams to explain the processes occurring in a plant when a growth response to light occurs.

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