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Challenge Questions

This page contains further questions on the subject of plant growth optimisation and are designed to stimulate more in-depth conversation and learning. These questions support students to think and write at the level of synthesis and understanding required for Merit and Excellence discussions and above.


1. The scientific research team developed understanding of the role of Auxin Binding Protein 1 (ABP1) in auxin action using two key biotechnologies:    

  • Transgenic plants 
  • Polymerase chain reaction 


By creating a transgenic plant where a gene could be turned on or off, the scientific team worked out what that ABP1 gene did in the cell and therefore the plant. 


(a) Explain how a transgenic plant is created and what biotechnologies are required to do this. 

(b) Describe what mechanism the team used to turn the gene on and off 

(c) Explain how PCR technologies are used to measure whether the gene is turned on or off 

(d) Why did they also need to make observations of the plant using microscopes and simple measurements of leaves and roots?



2. The scientific team found that as well as affecting shoots and leaves, inhibiting Auxin Binding Protein affected the growth of roots. As with the shoots they ran tests with and without ethylene to check that the gene was being turned off. 

  • The photomicrographs below show what the cells looked like in the roots 
  • The white arrows show how extensive the meristematic tissue was in the roots
  • Meristematic tissue is the tissue in plants that can still divide - it is undifferentiated  

We know that when ABP1 was inactive the roots did not grow. 

  • What does the information in the micrographs above tell us about the role of ABP1 in root growth? 
  • Why did having ABP1 turned off stop the roots from growing?