Chapter 15: Plant Growth
NCERT Solutions for CBSE Class 10 Biology — 18 solved questions with detailed explanations.
Solved Questions
Q1. The plant growth hormone responsible for cell elongation is:
- Gibberellin
- Cytokinin
- Auxin
- Ethylene
Difficulty: Easy · Topic: Plant Hormones
Solution
Auxin (IAA - Indole-3-acetic acid) promotes cell elongation, apical dominance, and phototropism.
Q2. Abscisic acid is known as the:
- Growth hormone
- Stress hormone
- Flowering hormone
- Ripening hormone
Difficulty: Easy · Topic: ABA
Solution
ABA is the 'stress hormone' - it promotes stomatal closure during water stress, inhibits growth, and promotes dormancy.
Q3. Ethylene promotes:
- cell division
- root growth
- stem elongation
- fruit ripening
Difficulty: Easy · Topic: Plant Growth
Q4. Photoperiodism was discovered by:
- Went
- Skoog
- Garner and Allard
- Darwin
Difficulty: Easy · Topic: Plant Growth
Solution
Garner and Allard.
Q5. Apical meristem is found at:
- leaf margins
- root and shoot tips
- lateral sides
- flower base
Difficulty: Easy · Topic: Plant Growth
Solution
root and shoot tips.
Q6. Lateral meristem causes:
- increase in length
- leaf growth
- flower growth
- increase in girth (secondary growth)
Difficulty: Easy · Topic: Plant Growth
Solution
increase in girth (secondary growth).
Q7. Intercalary meristem is found at:
- shoot tip
- root tip
- base of internodes
- lateral side
Difficulty: Easy · Topic: Plant Growth
Solution
base of internodes.
Q8. Auxin is produced mainly in:
- seeds
- roots only
- shoot apex and young leaves
- flowers
Difficulty: Easy · Topic: Plant Growth
Solution
shoot apex and young leaves.
Q9. Phototropism is growth in response to:
- chemicals
- gravity
- light
- touch
Difficulty: Easy · Topic: Plant Growth
Q10. Geotropism is growth in response to:
- chemicals
- touch
- gravity
- light
Difficulty: Easy · Topic: Plant Growth
Q11. Thigmotropism is growth in response to:
- light
- gravity
- chemicals
- touch/contact
Difficulty: Easy · Topic: Plant Growth
Q12. Long-day plants flower when:
- day length exceeds critical photoperiod
- always
- night is long
- never
Difficulty: Easy · Topic: Plant Growth
Solution
day length exceeds critical photoperiod.
Q13. Phytochrome is a:
- growth hormone
- enzyme
- vitamin
- photoreceptor pigment (Pr and Pfr forms)
Difficulty: Easy · Topic: Plant Growth
Solution
photoreceptor pigment (Pr and Pfr forms).
Q14. Dormancy is broken by:
- gibberellic acid, stratification, light
- ABA
- cytokinin
- ethylene
Difficulty: Easy · Topic: Plant Growth
Solution
gibberellic acid, stratification, light.
Q15. Gibberellins promote:
- stem elongation and bolting
- dormancy
- leaf fall
- root growth
Difficulty: Easy-Medium · Topic: Plant Growth
Solution
stem elongation and bolting.
Q16. Cytokinins promote:
- cell division
- cell elongation
- abscission
- dormancy
Difficulty: Easy-Medium · Topic: Plant Growth
Q17. Short-day plants flower when:
- continuous light
- continuous dark
- night length exceeds critical period
- day length exceeds
Difficulty: Easy-Medium · Topic: Plant Growth
Solution
night length exceeds critical period.
Q18. Vernalization is the effect of:
- cold treatment on flowering
- light on growth
- water on seeds
- gravity on roots
Difficulty: Easy-Medium · Topic: Plant Growth
Solution
cold treatment on flowering.
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