Pearson Edexcel A Level · Biology B (9BI0)

Chemical control in plants: Practice Questions

4 multiple-choice questions marked as you go, and 4 written questions with worked solutions. All on Chemical control in plants.

8 questions25 marksFree, no account

Question 1

1 mark

Phytochrome pigments exist in two interconvertible forms, \( P_r \) and \( P_{fr} \). Which of the following correctly describes the conversion that occurs when a plant is exposed to far-red light (wavelength approx. 730 nm)?

Question 2

1 mark

A short-day plant is grown in a laboratory under controlled conditions. Which of the following light treatments would most likely inhibit flowering in this plant?

Question 3

1 mark

Auxin is known to promote the transcription of specific genes related to cell wall loosening. Which statement best describes the mechanism by which auxin facilitates cell elongation in the shoot tip?

Question 4

1 mark

Apical dominance in plants is regulated by the interaction of different growth substances. Which of the following correctly describes the antagonistic relationship between auxin and cytokinins in this process?

Question 5

4 marks

Contrast the antagonistic roles of auxins and cytokinins in the regulation of apical dominance within a plant shoot.

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Question 6

6 marks

Discuss how phytochrome (\( P_{r} \) and \( P_{fr} \)) controls the flowering response in long-day plants, including the effect of light quality on the interconversion of these pigments.

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Question 7

5 marks

Apical dominance is a common phenomenon in plant growth where the central stem grows more strongly than the side stems. This is regulated by the interaction of different growth substances.

(a) Describe how auxin produced in the shoot apex maintains apical dominance and explain how the removal of the apex affects the growth of lateral buds.

(b) Plant growth substances often exhibit antagonistic effects. Discuss how the relationship between auxin and cytokinins determines the development of lateral buds.

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Question 8

6 marks

Plant growth substances like auxins and cytokinins often interact antagonistically.
(a) Explain how auxin produced in the apical meristem leads to apical dominance.
(b) Describe how the interaction between auxin and cytokinins determines the growth of lateral buds when the lead shoot is removed.

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