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 Regulation of Plant and Animal Systems: 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?

96%

114 rated

Answer

The term used to describe a plant's growth response to light is phototropism. This is the process where plants grow towards a light source, enabling them to maximize light absorption for photosynthesis.

Step 2

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

99%

104 rated

Answer

I would expect to see a growth response in treatments A, E, F, and G. In these treatments, the tips of the coleoptiles are exposed to light, which is crucial for phototropic responses.

Step 3

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

96%

101 rated

Answer

I expect to see a growth response in treatments A, E, F, and G because the tips of the coleoptiles are exposed to light. Light is necessary for phototropism since it influences the distribution of auxin, a plant hormone that regulates growth. In response to light, auxin accumulates on the shaded side of the plant, causing that side to grow faster than the illuminated side, leading to bending towards the light.

Step 4

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

98%

120 rated

Answer

To illustrate the process of phototropism:

Light Perception: The coleoptile detects the direction of light through photoreceptors.
Auxin Distribution: Auxin is redistributed to the shaded side of the coleoptile.
Growth Response: The accumulation of auxin on the shaded side promotes cell elongation, causing the plant to bend towards the light.

The following diagrams illustrate these steps:

Diagram 1: Light source on the right.

Light -------> 

   O (coleoptile)  
   /   
  /    
 /      
@ (auxin accumulation on the left)

Diagram 2: Resulting bend towards the light.

   O` (bent coleoptile)  
  /  
 /    
/     
Light ------>

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.

Join the SSCE students using SimpleStudy...