8.3.1 Phytochrome and IAA responses to environmental cues Quiz: Pearson Edexcel Biology, Unit 8

The 20 questions

1. Which group of plant hormones includes IAA (indoleacetic acid)?

   • Gibberellins
   • Cytokinins
   • Abscisic acids
   • Auxins

2. Which wavelength of light converts inactive phytochrome Pr into active Pfr?

   • 550 nm
   • 730 nm
   • 660 nm
   • 450 nm

3. Which wavelength of light converts active phytochrome Pfr back into Pr?

   • 730 nm
   • 660 nm
   • 520 nm
   • 400 nm

4. How does active phytochrome (Pfr) primarily influence plant cells?

   • Alters gene transcription
   • Inhibits water uptake
   • Destroys cell walls
   • Blocks protein translation

5. Which form of phytochrome directly triggers seed germination in most plants?

   • IAA
   • Chlorophyll
   • Pr
   • Pfr

6. Where does IAA accumulate in a plant shoot exposed to unilateral light?

   • Shoot apex
   • Root tip
   • Shaded side
   • Illuminated side

7. How does IAA promote cell elongation according to the acid growth hypothesis?

   • Decreased turgor pressure
   • Cell wall thickening
   • Cell wall loosening
   • Proton pump inhibition

8. How does active phytochrome Pfr stimulate the transcription of target genes?

   • Breaks down mRNA
   • Activates transcription factors
   • Inhibits RNA polymerase
   • Blocks nuclear pores

9. What happens to the proportion of Pfr in plants growing under shade?

   • It increases
   • It decreases
   • It doubles
   • It remains constant

10. What effect does a higher concentration of IAA have on shoot cells?

    • Cellular lysis
    • Increased elongation
    • Inhibited division
    • Decreased elongation

11. High concentrations of IAA have what effect on root growth?

    • Has no effect
    • Inhibits growth
    • Promotes cell division
    • Stimulates growth

12. Which plant response to light cues is directly mediated by phytochrome?

    • Phototropism
    • Shade avoidance
    • Thigmotropism
    • Geotropism

13. A Pfr proportion falls from 0.6 to 0.2 in shade. What is the percentage decrease?

    • 66.7%
    • 40.0%
    • 33.3%
    • 60.0%

14. Through which plant cells is IAA transported in a polar manner?

    • Sclerenchyma fibres
    • Parenchyma cells
    • Xylem vessels
    • Sieve tube elements

15. What effect does removing the shoot apex have on lateral buds?

    • Prevents cell division
    • Causes abscission
    • Inhibits growth
    • Promotes growth

16. Which molecule directly regulates plant responses to light via gene transcription?

    • Cytokinin
    • Abscisic acid
    • Gibberellin
    • Phytochrome

17. Red light causes which conversion of phytochrome?

    • Pfr to IAA
    • Pr to mRNA
    • Pfr to Pr
    • Pr to Pfr

18. Which light wavelength promotes seed germination in light-sensitive seeds?

    • Red light
    • Green light
    • Far-red light
    • Blue light

19. How sensitive is root tissue to IAA compared to shoot tissue?

    • Less sensitive
    • More sensitive
    • Completely insensitive
    • Equally sensitive

20. What determines the final active form of phytochrome present in a plant?

    • Soil moisture level
    • Total light intensity
    • Last wavelength absorbed
    • Ambient temperature

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