Plant Responses
Q1.
Hormones called auxins control plant growth.
A student investigated plant growth responses in roots.
This is the method used.
1.      Grow three bean seeds until their roots are 1 cm long.
2.      Attach the three bean seeds to moist cotton wool in a Petri dish.
Each bean seed root should point in a different direction.
3.      Fix the Petri dish vertically for 2 days in the dark.
Figure 1 shows the results.
Figure 1
 
(a)     Describe the direction of growth of the bean roots after 2 days.
Give one reason for this growth response.
Direction of root growth ________________________________________________
Reason ____________________________________________________________
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(2)
(b)     The student then noticed the shoots growing from the seeds.
He then:
1.      put a light above the Petri dish but did not move the seeds
2.      allowed the seeds to grow for 2 more days.
Predict the direction of growth of the bean shoots after 2 days.
Give one reason for your prediction.
Direction of root growth ________________________________________________
Reason ____________________________________________________________
(2)
(c)     Ethene is a plant hormone.
Ethene causes fruit to ripen.
Scientists measured the concentration of ethene found in fruit at different stages of ripeness.
Figure 2 shows the results.
Figure 2
 
At which stage of ripeness is there most ethene?
 
Tick one box.	 	
Stage 1		
Stage 2		
Stage 3		
Stage 4		
Stage 5		
(1)
(d)     Suggest how the scientists can find out if the result for Stage 1 was an anomaly.
___________________________________________________________________
___________________________________________________________________
(1)
(e)     Gibberellins are a different type of plant hormone.
Farmers growing cotton plants in cold climates sometimes soak their seeds in a solution of gibberellins before planting the seeds.
Suggest an advantage of soaking seeds in a gibberellin solution in cold climates.
___________________________________________________________________
___________________________________________________________________
(1)
(Total 7 marks)