Practise 33 exam-style questions on Use of plant hormones (HT only) for AQA GCSE Biology. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
33 questions
2–5 marks each
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20 questions, marked as you go
Sample questions with model answers
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Question 1
2 marks
Why is ethene used to ripen climacteric fruits but generally not used for non-climacteric fruits? (HT only)
Model answer
climacteric fruits respond to ethene and show an ethylene-associated burst in respiration and ripening (e.g., bananas, tomatoes); non-climacteric fruits do not respond to ethene in the same way and do not undergo climacteric ripening
Explanation
Climacteric fruits have an ethylene-regulated ripening phase and can be induced to ripen by ethene. Non-climacteric fruits lack this ethylene response and therefore ethene application does not trigger normal ripening processes.
Mark scheme
1 mark
climacteric fruits respond to ethene and ripen due to ethene-triggered processes
1 mark
non-climacteric fruits do not respond to ethene in the same way so ethene is ineffective
Question 2
3 marks
Describe how auxins and cytokinins can be used together in tissue culture to produce shoots and roots. (HT only)
Model answer
ratio matters: high cytokinin:auxin promotes shoot formation; high auxin:cytokinin promotes root formation; both hormones on medium control cell division and differentiation into shoots or roots
Explanation
In tissue culture, the balance of auxin and cytokinin determines outcome: more cytokinin relative to auxin induces shoot organogenesis, while more auxin relative to cytokinin induces root formation. These hormones regulate cell division and differentiation.
Mark scheme
1 mark
high cytokinin to auxin ratio promotes shoot formation
1 mark
high auxin to cytokinin ratio promotes root formation
1 mark
hormone ratios control cell division/differentiation in cultured tissues
Question 3
3 marks
A scientist wants to produce seedless grapes. Which hormone treatment(s) might she use and at what stage? Explain the biological rationale. (HT only)
Model answer
apply auxin or gibberellin at/near flowering to induce parthenocarpy (fruit set without fertilisation) producing seedless fruit; auxin application will stimulate ovary to develop into fruit without pollination
Explanation
Treatment with auxins or gibberellins around flowering can induce parthenocarpy, causing the ovary to develop into fruit without fertilisation, thereby producing seedless grapes commercially.
Mark scheme
1 mark
apply auxin or gibberellin at flowering/just after to induce parthenocarpy
1 mark
parthenocarpy = fruit development without fertilisation (seedless fruit)
1 mark
hormone stimulates ovary growth and fruit set without pollination
Question 4
4 marks
Describe an experiment to determine the optimal concentration of auxin for rooting a particular species of cutting. Include control, variables, and how you would determine the optimal concentration. (HT only)
Model answer
use series of auxin concentrations (including zero control) on groups of identical cuttings; keep other conditions constant (light, temp, moisture, cutting size); measure rooting success (percentage rooted), number/length of roots after set time; optimal concentration is that giving highest percentage or best root quality without phytotoxicity; repeat and calculate means
Explanation
Testing a gradient of auxin concentrations with a control and replicates while keeping conditions constant allows identification of the concentration that maximises rooting percentage and root quality. The optimal concentration is where benefit is maximal without toxic effects.
Mark scheme
1 mark
set up groups of identical cuttings exposed to a range of auxin concentrations plus a zero-concentration control
1 mark
control variables: light, temperature, moisture, cutting size/age and number of replicates
1 mark
measure rooting success (percentage rooted) and root quality (number/length) after fixed period
1 mark
optimal concentration is the one producing highest rooting percentage / best root quality without damage; use replicates and means
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