ROUND 2 SPEED RACE
ONE EIGHTH STAGE 2026
Contest 1
Prempeh College: 66
West Africa SHS: 30
Kumasi Girls’ SHS: 19
Contest 2
Keta SHTS: 56
Kadjebi Asato SHS: 28
Anum Presby SHS: 19
Contest 3
Ghana National College: 38
St. Monica’s SHS: 22
Presby SHS, Suhum: 16
QUESTION
Name the primary hormone responsible for phototropism.
ANSWER: Auxin
EXPLANATION
Auxin accumulates on the shaded side of a shoot, stimulating greater cell elongation there than on the light-exposed side, causing the shoot to bend towards the light source (positive phototropism).
PRACTICE QUESTIONS
1. Where is auxin mainly made in a plant?
ANSWER: In the shoot tips (apical meristems).
2. What effect does auxin have on cells of the shoot?
ANSWER: It makes them elongate.
3. What is apical dominance?
ANSWER: The tip of the shoot stops the growth of lateral buds.
4. What is phototropism?
ANSWER: Growth of a plant in response to the direction of light.
5. Which plant part was used in the classic phototropism experiments of Darwin and Went?
ANSWER: The coleoptile of grass seedlings.
6. Do shoots show positive or negative phototropism?
ANSWER: Positive.
7. Do roots usually show positive or negative phototropism?
ANSWER: Negative.
8. In which direction does auxin move in a shoot?
ANSWER: Down from the tip (polar transport).
9. Name two synthetic auxins.
ANSWER: 2,4-D and NAA.
10. How is auxin used in rooting powder?
ANSWER: It makes cuttings form roots.
11. What effect does a high concentration of auxin have on roots?
ANSWER: It inhibits their growth.
12. What is the acid growth hypothesis?
ANSWER: Auxin makes cells pump out hydrogen ions, loosening the wall so it stretches.