MCQs on Plant Growth and Development – Class 11 Biology

MCQs on Plant Growth and Development – CBSE Class 11 Biology (Unit IV | NCERT-Based)

CBSE Class 11 Biology – MCQs with Answers and Explanations

Unit IV: Plant Physiology

Topic: Plant Growth and Development

Section A: Growth, Development & Growth Phases (Q1–Q10)

Q1. Plant growth is defined as:

A. Qualitative change only
B. Reversible increase in size
C. Irreversible increase in size and mass
D. Seasonal change in plants

Answer: C
Explanation: Growth is a permanent and irreversible increase in size, mass, or volume due to cell division and enlargement.

Q2. Which type of growth is characteristic of plants?

A. Determinate growth
B. Indeterminate growth
C. Limited growth
D. Fixed growth

Answer: B
Explanation: Plants show indeterminate growth due to the presence of meristems.

Q3. Increase in cell number occurs due to:

A. Cell elongation
B. Cell differentiation
C. Cell division
D. Cell maturation

Answer: C
Explanation: Growth in number is a result of mitotic cell division.

Q4. Increase in cell size mainly occurs due to:

A. DNA replication
B. Vacuolation
C. Protein breakdown
D. Respiration

Answer: B
Explanation: Cell enlargement is primarily due to vacuole formation and water uptake.

Q5. Growth is maximum during which phase of growth curve?

A. Lag phase
B. Log phase
C. Stationary phase
D. Senescence phase

Answer: B
Explanation: The log (exponential) phase shows the fastest growth rate.

Q6. The graph representing plant growth is usually:

A. Linear curve
B. Bell-shaped curve
C. Sigmoid curve
D. Circular curve

Answer: C
Explanation: Plant growth follows a sigmoid (S-shaped) curve.

Q7. Which phase of growth shows slow initial growth?

A. Log phase
B. Stationary phase
C. Lag phase
D. Senescence

Answer: C
Explanation: Lag phase involves preparatory metabolic activities.

Q8. Development in plants refers to:

A. Growth only
B. Differentiation only
C. Growth and differentiation
D. Reproduction only

Answer: C
Explanation: Development includes growth, differentiation, and maturation.

Q9. Meristematic tissues are responsible for:

A. Respiration
B. Photosynthesis
C. Growth
D. Translocation

Answer: C
Explanation: Meristems actively divide, enabling continuous growth.

Q10. Which meristem is responsible for increase in length?

A. Lateral meristem
B. Apical meristem
C. Intercalary meristem
D. Secondary meristem

Answer: B
Explanation: Apical meristems cause primary growth.

Section B: Plant Growth Regulators – General Concepts (Q11–Q20)

Q11. Plant growth regulators are:

A. Nutrients
B. Hormones synthesized in roots only
C. Organic compounds affecting growth in small amounts
D. Inorganic salts

Answer: C
Explanation: Plant growth regulators (PGRs) are organic substances active in minute quantities.

Q12. Which of the following is NOT a plant growth regulator?

A. Auxin
B. Gibberellin
C. Cytokinin
D. Calcium

Answer: D
Explanation: Calcium is a mineral nutrient, not a PGR.

Q13. Which plant hormone was the first to be discovered?

A. Cytokinin
B. Auxin
C. Gibberellin
D. Ethylene

Answer: B
Explanation: Auxin was the first discovered plant hormone.

Q14. Growth promoters include:

A. Auxins, gibberellins, cytokinins
B. Abscisic acid only
C. Ethylene only
D. ABA and ethylene

Answer: A
Explanation: These hormones promote cell division, elongation, and differentiation.

Q15. Growth inhibitors include:

A. Auxin and cytokinin
B. Gibberellin and ethylene
C. Abscisic acid and ethylene
D. Auxin and gibberellin

Answer: C
Explanation: ABA and ethylene generally inhibit growth.

Q16. Which hormone is known as stress hormone?

A. Auxin
B. Gibberellin
C. Cytokinin
D. Abscisic acid

Answer: D
Explanation: ABA helps plants cope with stress conditions.

Q17. Plant growth regulators are synthesized mainly in:

A. Roots only
B. Leaves only
C. Meristematic tissues
D. Mature tissues only

Answer: C
Explanation: Meristems and young tissues synthesize PGRs.

Q18. Which plant hormone is gaseous in nature?

A. Auxin
B. Gibberellin
C. Cytokinin
D. Ethylene

Answer: D
Explanation: Ethylene is the only gaseous hormone.

Q19. Which hormone regulates cell division?

A. Auxin
B. Cytokinin
C. Ethylene
D. ABA

Answer: B
Explanation: Cytokinins promote cytokinesis.

Q20. Which hormone promotes stem elongation?

A. Cytokinin
B. Ethylene
C. Gibberellin
D. ABA

Answer: C
Explanation: Gibberellins stimulate internode elongation.

Section C: Individual Plant Hormones & Functions (Q21–Q35)

Q21. Auxins are synthesized mainly in:

A. Roots
B. Mature leaves
C. Shoot apex
D. Seeds only

Answer: C
Explanation: Auxins are produced in apical buds and young leaves.

Q22. Auxin promotes growth by:

A. Increasing respiration
B. Cell wall acidification
C. Protein breakdown
D. Inhibiting elongation

Answer: B
Explanation: Auxins activate proton pumps, loosening cell walls.

Q23. Apical dominance is due to:

A. Gibberellin
B. Cytokinin
C. Auxin
D. Ethylene

Answer: C
Explanation: Auxin from apical bud suppresses lateral buds.

Q24. Removal of apical bud results in:

A. Reduced branching
B. Increased lateral growth
C. Leaf fall
D. Reduced flowering

Answer: B
Explanation: Loss of apical dominance promotes branching.

Q25. Which hormone delays senescence?

A. Auxin
B. Gibberellin
C. Cytokinin
D. Ethylene

Answer: C
Explanation: Cytokinins delay aging of leaves.

Q26. Gibberellins promote:

A. Dormancy
B. Seed germination
C. Leaf abscission
D. Fruit ripening

Answer: B
Explanation: Gibberellins activate enzymes during germination.

Q27. Bolting in rosette plants is caused by:

A. Auxin
B. Cytokinin
C. Ethylene
D. Gibberellin

Answer: D
Explanation: Gibberellins induce rapid stem elongation (bolting).

Q28. Which hormone promotes fruit ripening?

A. Auxin
B. Cytokinin
C. Ethylene
D. Gibberellin

Answer: C
Explanation: Ethylene accelerates ripening of fruits.

Q29. Abscission of leaves is promoted by:

A. Cytokinin
B. Gibberellin
C. Ethylene
D. Auxin

Answer: C
Explanation: Ethylene promotes leaf and fruit abscission.

Q30. Which hormone maintains seed dormancy?

A. Gibberellin
B. Cytokinin
C. Ethylene
D. Abscisic acid

Answer: D
Explanation: ABA induces and maintains seed dormancy.

Q31. Which hormone promotes lateral bud growth?

A. Auxin
B. Cytokinin
C. Ethylene
D. ABA

Answer: B
Explanation: Cytokinin counteracts apical dominance.

Q32. Fruit growth without fertilization is called:

A. Pollination
B. Parthenocarpy
C. Apomixis
D. Hybridization

Answer: B
Explanation: Parthenocarpy leads to seedless fruits.

Q33. Parthenocarpy can be induced by:

A. ABA
B. Cytokinin
C. Auxin
D. Ethylene

Answer: C
Explanation: Auxins can induce fruit development without seeds.

Q34. Which hormone inhibits growth?

A. Auxin
B. Gibberellin
C. Cytokinin
D. Abscisic acid

Answer: D
Explanation: ABA is a growth inhibitor.

Q35. Leaf senescence is delayed by:

A. Ethylene
B. Cytokinin
C. ABA
D. Auxin

Answer: B
Explanation: Cytokinins maintain chlorophyll and protein content.

Section D: Photoperiodism, Vernalisation & Movements (Q36–Q50)

Q36. Photoperiodism refers to response of plants to:

A. Temperature
B. Light intensity
C. Duration of light
D. Light wavelength

Answer: C
Explanation: Photoperiodism depends on day length.

Q37. Short-day plants flower when day length is:

A. Longer than critical period
B. Equal to critical period
C. Shorter than critical period
D. Independent of light

Answer: C
Explanation: Short-day plants require long nights.

Q38. Long-day plants flower when day length is:

A. Short
B. Equal to night
C. Longer than critical period
D. Independent of light

Answer: C
Explanation: Long-day plants need longer daylight.

Q39. Which plant flowers irrespective of photoperiod?

A. Rice
B. Wheat
C. Tomato
D. Soybean

Answer: C
Explanation: Tomato is a day-neutral plant.

Q40. Photoperiodic stimulus is perceived by:

A. Roots
B. Leaves
C. Stem
D. Flowers

Answer: B
Explanation: Leaves perceive photoperiodic signals.

Q41. Vernalisation is induced by:

A. High temperature
B. Long days
C. Low temperature
D. Darkness

Answer: C
Explanation: Vernalisation requires prolonged cold exposure.

Q42. Vernalisation promotes:

A. Seed dormancy
B. Leaf fall
C. Flowering
D. Senescence

Answer: C
Explanation: Vernalisation accelerates flowering.

Q43. The hormone involved in vernalisation is believed to be:

A. Auxin
B. Gibberellin
C. Cytokinin
D. Florigen

Answer: D
Explanation: Florigen is a hypothetical flowering hormone.

Q44. Growth movements dependent on direction of stimulus are called:

A. Nastic movements
B. Turgor movements
C. Tropic movements
D. Autonomic movements

Answer: C
Explanation: Tropic movements are directional growth responses.

Q45. Bending of shoot towards light is:

A. Geotropism
B. Hydrotropism
C. Phototropism
D. Chemotropism

Answer: C
Explanation: Shoots show positive phototropism.

Q46. Root bending towards gravity shows:

A. Positive phototropism
B. Negative geotropism
C. Positive geotropism
D. Hydrotropism

Answer: C
Explanation: Roots show positive geotropism.

Q47. Nastic movements are:

A. Directional
B. Growth-based
C. Non-directional
D. Permanent

Answer: C
Explanation: Nastic movements depend on stimulus intensity, not direction.

Q48. Opening and closing of flowers due to light is:

A. Thigmonasty
B. Photonasty
C. Nyctinasty
D. Seismonasty

Answer: B
Explanation: Photonasty occurs in response to light.

Q49. Movement of Mimosa pudica leaves is an example of:

A. Tropism
B. Growth movement
C. Nastic movement
D. Chemotropism

Answer: C
Explanation: Mimosa shows thigmonastic movement.

Q50. Plant growth and development are controlled by:

A. Only hormones
B. Only environmental factors
C. Genes, hormones, and environment
D. Light only

Answer: C
Explanation: Growth and development depend on genetic, hormonal, and environmental factors.