Plant Growth and Development
Plant growth is an irreversible increase in size, while development includes all changes from germination to senescence. It occurs in three phases—cell division, elongation, and differentiation—following an S-shaped growth curve. Phytohormones like auxins, gibberellins, cytokinins, ethylene, and abscisic acid regulate growth, dormancy, and flowering. External factors like light, temperature, and gravity also influence development. Photoperiodism and vernalization control flowering, while tropisms help plants respond to stimuli. Understanding these processes is crucial for improving agriculture and crop productivity.
1. Which plant hormone is primarily responsible for cell elongation?
a) Cytokinin
b) Auxin
c) Gibberellin
d) Ethylene
Answer: b) Auxin
2. What is the function of gibberellins in plants?
a) Inhibiting seed germination
b) Promoting cell division
c) Stimulating stem elongation
d) Delaying fruit ripening
Answer: c) Stimulating stem elongation
3. Which plant hormone is known as the "stress hormone"?
a) Abscisic acid
b) Ethylene
c) Auxin
d) Gibberellin
Answer: a) Abscisic acid
4. Photoperiodism in plants is regulated by which pigment?
a) Chlorophyll
b) Carotenoids
c) Phytochrome
d) Anthocyanins
Answer: c) Phytochrome
5. Vernalization is required for which type of plants?
a) Short-day plants
b) Long-day plants
c) Biennials
d) Perennials
Answer: c) Biennials
6. Which plant hormone promotes fruit ripening?
a) Auxin
b) Cytokinin
c) Gibberellin
d) Ethylene
Answer: d) Ethylene
7. The formation of root nodules in leguminous plants is promoted by which hormone?
a) Cytokinin
b) Abscisic acid
c) Gibberellin
d) Auxin
Answer: d) Auxin
8. The dormancy of seeds is broken by which hormone?
a) Abscisic acid
b) Gibberellin
c) Cytokinin
d) Ethylene
Answer: b) Gibberellin
9. Which of the following is an example of a long-day plant?
a) Rice
b) Wheat
c) Tomato
d) Sunflower
Answer: b) Wheat
10. Which process is controlled by abscisic acid?
a) Seed dormancy
b) Flowering
c) Stem elongation
d) Root formation
Answer: a) Seed dormancy
11. The term "tropism" refers to:
a) Movement in response to gravity
b) Growth response to an external stimulus
c) Movement of leaves
d) Development of flowers
Answer: b) Growth response to an external stimulus
12. Which plant hormone is mainly responsible for apical dominance?
a) Cytokinin
b) Gibberellin
c) Auxin
d) Ethylene
Answer: c) Auxin
13. Ethylene is a gaseous hormone responsible for:
a) Cell elongation
b) Fruit ripening
c) Leaf expansion
d) Root growth
Answer: b) Fruit ripening
14. Which plant movement is influenced by light?
a) Hydrotropism
b) Geotropism
c) Phototropism
d) Thigmotropism
Answer: c) Phototropism
15. Cytokinins promote which plant process?
a) Leaf abscission
b) Cell division
c) Seed dormancy
d) Fruit ripening
Answer: b) Cell division
16. Which of the following is a function of abscisic acid?
a) Stimulating seed germination
b) Delaying leaf senescence
c) Closing of stomata
d) Promoting root elongation
Answer: c) Closing of stomata
17. The plant growth regulator used to induce flowering in pineapple is:
a) Gibberellin
b) Auxin
c) Ethylene
d) Cytokinin
Answer: c) Ethylene
18. The hormone responsible for bolting in rosette plants is:
a) Auxin
b) Cytokinin
c) Gibberellin
d) Ethylene
Answer: c) Gibberellin
19. Which hormone helps in delaying senescence?
a) Auxin
b) Cytokinin
c) Ethylene
d) Abscisic acid
Answer: b) Cytokinin
20. The phenomenon of seed dormancy is mainly due to:
a) High levels of gibberellins
b) Absence of abscisic acid
c) High levels of abscisic acid
d) Low levels of cytokinin
Answer: c) High levels of abscisic acid
21. The hormone responsible for the opening of stomata is:
a) Ethylene
b) Cytokinin
c) Auxin
d) Gibberellin
Answer: b) Cytokinin
22. Which of the following is an artificial growth regulator?
a) IAA
b) NAA
c) Cytokinin
d) Ethylene
Answer: b) NAA
23. Which type of growth curve is shown by plants?
a) Linear
b) Exponential
c) Sigmoid
d) Parabolic
Answer: c) Sigmoid
24. In plants, the process of senescence is controlled by:
a) Cytokinins
b) Gibberellins
c) Ethylene
d) Abscisic acid
Answer: c) Ethylene
25. Which hormone is responsible for root initiation in stem cuttings?
a) Gibberellin
b) Auxin
c) Cytokinin
d) Ethylene
Answer: b) Auxin
26. The response of plants to the duration of light and dark periods is known as:
a) Vernalization
b) Phototropism
c) Photoperiodism
d) Nastic movement
Answer: c) Photoperiodism
27. Which plant hormone is used in tissue culture for cell differentiation?
a) Gibberellin
b) Auxin
c) Cytokinin
d) Ethylene
Answer: c) Cytokinin
28. The swelling of seeds during germination is due to:
a) Osmosis
b) Respiration
c) Photosynthesis
d) Transpiration
Answer: a) Osmosis
29. Root cap is responsible for which type of movement in roots?
a) Phototropism
b) Geotropism
c) Thigmotropism
d) Hydrotropism
Answer: b) Geotropism
30. The growth of pollen tubes toward ovules is an example of:
a) Chemotropism
b) Geotropism
c) Thigmotropism
d) Phototropism
Answer: a) Chemotropism
31. Which plant hormone is responsible for the shedding of leaves?
a) Gibberellin
b) Cytokinin
c) Abscisic acid
d) Auxin
Answer: c) Abscisic acid
32. Which hormone helps in fruit enlargement?
a) Cytokinin
b) Gibberellin
c) Abscisic acid
d) Ethylene
Answer: b) Gibberellin
33. Which of the following is an effect of ethylene in plants?
a) Promotes root elongation
b) Delays fruit ripening
c) Enhances seed dormancy
d) Induces senescence
Answer: d) Induces senescence
34. Which process is regulated by phytochrome in plants?
a) Photosynthesis
b) Photoperiodism
c) Transpiration
d) Respiration
Answer: b) Photoperiodism
35. What is the primary role of gibberellins in seed germination?
a) Breaking seed dormancy
b) Preventing water loss
c) Stimulating root growth
d) Closing stomata
Answer: a) Breaking seed dormancy
36. Which plant hormone is mainly responsible for fruit setting?
a) Cytokinin
b) Auxin
c) Gibberellin
d) Ethylene
Answer: b) Auxin
37. The bending of plant shoots towards light is called:
a) Geotropism
b) Hydrotropism
c) Phototropism
d) Thigmotropism
Answer: c) Phototropism
38. The effect of auxins was first observed in:
a) Root tips
b) Shoot tips
c) Leaf tips
d) Flower buds
Answer: b) Shoot tips
39. Which of the following is a synthetic auxin?
a) IAA
b) NAA
c) ABA
d) Ethylene
Answer: b) NAA
40. Which plant hormone promotes seed dormancy?
a) Cytokinin
b) Gibberellin
c) Abscisic acid
d) Ethylene
Answer: c) Abscisic acid
41. The growth phase in which cells increase in size is called:
a) Cell division phase
b) Cell elongation phase
c) Maturation phase
d) Dormancy phase
Answer: b) Cell elongation phase
42. Which plant movement occurs in response to water?
a) Phototropism
b) Geotropism
c) Hydrotropism
d) Thigmotropism
Answer: c) Hydrotropism
43. What is the main site of auxin synthesis in plants?
a) Roots
b) Stem
c) Shoot apices
d) Leaves
Answer: c) Shoot apices
44. The hormone used for inducing flowering in mango trees is:
a) Auxin
b) Cytokinin
c) Ethylene
d) Abscisic acid
Answer: c) Ethylene
45. Gibberellins were first discovered in:
a) Bacteria
b) Algae
c) Fungi
d) Plants
Answer: c) Fungi
46. The term "thigmotropism" refers to plant movement in response to:
a) Light
b) Gravity
c) Water
d) Touch
Answer: d) Touch
47. Which plant hormone is involved in seed and bud dormancy?
a) Cytokinin
b) Abscisic acid
c) Gibberellin
d) Ethylene
Answer: b) Abscisic acid
48. Which hormone is responsible for the elongation of internodes?
a) Auxin
b) Cytokinin
c) Gibberellin
d) Ethylene
Answer: c) Gibberellin
49. Which of the following hormones is involved in apical dominance?
a) Cytokinin
b) Ethylene
c) Abscisic acid
d) Auxin
Answer: d) Auxin
50. Which hormone is used to induce parthenocarpy (seedless fruit formation)?
a) Gibberellin
b) Cytokinin
c) Ethylene
d) Abscisic acid
Answer: a) Gibberellin
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