Correct Answer: (d)
Phytohormones are chemical substances produced naturally in plants that regulate growth and physiological processes.
Q3. Which one of the following generally acts as an antagonist to gibberellins?
Correct Answer: (c)
ABA acts as an antagonist to Gibberellins (e.g., in seed dormancy vs germination).
Q4. Ethylene gas is used for
Correct Answer: (b)
Ethylene is used for fruit ripening.
Q5. Removal of apical bud results in
Correct Answer: (d)
Removal of apical dominance promotes lateral branching.
Q6. What is the site of perception of photoperiod necessary for induction of flowering in plants ?
Correct Answer: (d)
Leaves perceive the photoperiodic stimulus.
Q7. A few normal seedlings of tomato were kept in a dark room. After a few days they were found to have become white-coloured like albinos. Which of the following terms will you use to describe them?
Correct Answer: (c)
Etiolation is the condition of plants grown in partial or complete absence of light, characterized by long, weak stems and pale yellow leaves (chlorosis).
Q9. What causes a green plant exposed to the light on only one side, to bend toward the source of light as it grows ?
Correct Answer: (c)
Auxin moves to the shaded side, causing cells there to elongate more than on the lighted side, resulting in bending towards light.
Q10. What breaks bud dormancy of potato tuber?
Correct Answer: (a)
Gibberellins break dormancy.
Q11. The pine apple which under natural conditions is difficult to blossom has been made to produce fruits throughout the year by application of
Correct Answer: (b)
Synthetic auxins like NAA and 2,4-D are used to induce flowering in pineapple.
Q12. In short-day plants, flowering is induced by
Correct Answer: (b)
Short-day plants require uninterrupted long night below a critical photoperiod.
Q13. Which one of the following acids is a derivative of carotenoids ?
Correct Answer: (c)
Abscisic acid (ABA) is a derivative of carotenoids.
Q14. Bananas can be prevented from over-ripening by
Correct Answer: (c)
Ascorbic acid is an antioxidant that can delay ripening/browning.
Q15. Vernalization stimulates flowering in
Correct Answer: (c)
Carrot is a biennial plant requiring vernalization for flowering.
Q16. Seed dormancy is due to the
Correct Answer: (b)
ABA induces seed dormancy.
Q17. Cytokinins
Correct Answer: (c)
Cytokinins delay senescence by retaining chlorophyll and nutrients.
Q18. Removal of shoot tips is a very useful technique to boost the production of tealeaves. This is because :
Correct Answer: (d)
Apical dominance is caused by auxin in the shoot tip. Removing the tip removes auxin, allowing lateral buds to grow and producing more tea leaves.
Q19. Movement of auxin is
Correct Answer: (b)
Auxin transport is polar, primarily basipetal in stems.
Q20. Apical dominance is caused by
Correct Answer: (d)
Auxin produced in the shoot tip suppresses lateral buds.
Q21. Which is employed for artificial ripening of banana fruits?
Correct Answer: (c)
Ethylene is the fruit ripening hormone.
Q22. The pigment, that absorbs red and far red light in plants, is
Correct Answer: (c)
Phytochrome absorbs red and far-red light and regulates photoperiodic responses.
Q23. Which combination of gases is suitable for fruit ripening?
Correct Answer: (d)
Ethylene (C2H4) promotes ripening. CO2 usually inhibits it, but in specific controlled atmospheres, mixtures are used. Among options, only (d) contains Ethylene.
Q24. A chemical believed to be involved in flowering is
Correct Answer: (c)
Florigen is the hypothetical flowering hormone.
Q25. “Foolish seedling” disease of rice led to the discovery of
Correct Answer: (d)
Bakanae disease (Foolish seedling) caused by Gibberella fujikuroi led to discovery of Gibberellins (GA).
Q26. Fruit and leaf drop at early stages can be prevented by the application of:
Correct Answer: (b)
Auxins prevent premature abscission of plant organs like leaves and fruits.
Q27. During seed germination its stored food is mobilized
Correct Answer: (c)
Gibberellins stimulate the synthesis of hydrolytic enzymes (like alpha-amylase) to mobilize stored food during germination.
Q28. Hormone primarily connected with cell division is
Q36. Tendrils exhibit/twining of tendrils is due to
Correct Answer: (a)
Thigmotropism is growth response to touch, seen in tendrils.
Q37. Senescence as an active developmental cellular process in the growth and functioning of a flowering plant, is indicated in
Correct Answer: (b)
Senescence is the period between reproductive maturity and death of a plant or a part of it. Leaf abscission is an active developmental cellular process indicating senescence.
Q38. Which of the following is not an inhibitory substance governing seed dormancy?
Correct Answer: (d)
Gibberellic acid breaks seed dormancy and promotes germination. Others are inhibitors.
Q39. What will be the effect on phytochrome in a plant subjected to continuous red light?
Correct Answer: (d)
Under continuous red light, interconversion maintains equilibrium of phytochrome forms.
Q40. The method that renders the seed coat permeable to water so that embryo expansion is not physically retarded is
Correct Answer: (d)
Scarification breaks or weakens the seed coat to allow water uptake.
Q41. Leaves of many grasses are capable of folding and unfolding because they
Correct Answer: (c)
Bulliform cells in grasses allow leaves to roll up during water stress to reduce transpiration.
Q42. It takes very long time for pineapple plants to produce flowers. Which combination of hormones can be applied to artificially induce flowering in pineapple plants throughout the year to increase yield?
Correct Answer: (a)
Auxins (like NAA, 2,4-D) and Ethylene are used to induce flowering in pineapple.
Q43. A plant hormone used for inducing morphogenesis in plant tissue culture is
Correct Answer: (b)
Cytokinins (with Auxins) are used for morphogenesis (organogenesis).
Q44. Which one increases in the absence of light?
Correct Answer: (c)
In darkness, etiolation causes elongation of internodes.
Q45. Abscisic acid controls
Correct Answer: (b)
ABA promotes abscission (leaf fall) and dormancy.
Q46. Plants deficient of element zinc, show its effect on the biosynthesis of plant growth hormone
Correct Answer: (b)
Zinc is required for the synthesis of Tryptophan, which is the precursor of Auxin (IAA).
Q47. Mowing grass lawn facilitates better maintenance because
Correct Answer: (b)
Removing tips removes apical dominance, allowing intercalary meristems (in grasses) and lateral buds to grow, making turf dense.
Q48. Flowering dependent on cold treatment is
Correct Answer: (d)
Vernalisation is induction of flowering by low temperature treatment.
Q49. The response of different organisms to environmental rhythms of light and darkness is called
Correct Answer: (b)
Photoperiodism is the response of organisms to day-length changes.
Q50. Anthesis is a phenomenon which refers to
Correct Answer: (d)
Anthesis is the period during which a flower is fully open and functional.
Q51. Auxin can be bioassayed by :
Correct Answer: (d)
Avena coleoptile curvature test is a bioassay for Auxins. Lettuce hypocotyl elongation is for Gibberellins.
Q52. Which of the following prevents fall of fruits?
Correct Answer: (b)
NAA (Synthetic Auxin) prevents premature fruit drop.
Q53. Phototropic and geotropic movements are linked to :
Correct Answer: (c)
Auxin distribution causes these tropisms.
Q54. The Avena curvature is used for bioassay of
Correct Answer: (c)
The Avena coleoptile curvature test is the bioassay for Auxin (IAA).
Q55. Highest auxin concentration occurs
Correct Answer: (a)
Auxin is synthesized in growing tips (apices).
Q56. Cut or excised leaves remain green for long if induced to root or dipped in
Correct Answer: (b)
Cytokinins delay senescence (loss of chlorophyll).
Q57. Opening of floral buds into flowers, is a type of
Correct Answer: (c)
Opening of floral buds into flowers is a type of autonomic movement of growth called Epinasty/Hyponasty (Nastic movements).
Q58. The hormone responsible for apical dominance is
Q60. What reason will you assign for coconut milk used in tissue culture?
Correct Answer: (b)
Coconut milk is rich in Cytokinins (Zeatin), promoting cell division.
Q61. Auxetic growth is
Correct Answer: (a)
Auxetic growth involves increase in cell size/volume without cell division.
Q62. Phytochrome is involved in
Correct Answer: (c)
Phytochrome regulates photoperiodic responses in plants.
Q63. Which of the following hormones can replace vernalisation?
Correct Answer: (c)
Gibberellins can substitute cold treatment required for flowering.
Q64. Which one is a long-day plant?
Correct Answer: (d)
Spinach is a long-day plant requiring longer photoperiod for flowering.
Q65. Name the plant growth regulator which upon spraying on sugarcane crop, increases the length of stem, thus increasing the yield of sugarcane crop.
Correct Answer: (a)
Gibberellins increase the length of internodes in sugarcane stems, increasing yield.
Q66. Abscisic acid causes
Correct Answer: (a)
ABA induces stomatal closure under water stress.
Q67. Which of the following movement is not related to auxin level?
Correct Answer: (c)
Nyctinastic movements are turgor movements (nastic), not growth movements regulated by auxin like tropisms.
Q68. What is a stress hormone? or The hormone produced during adverse environmental conditions is
Correct Answer: (d)
ABA is the stress hormone.
Q69. Dr. F. Went noted that if coleoptile tips were removed and placed on agar for one hour, the agar would produce a bending when placed on one side of freshly-cut coleoptile stumps. Of what significance is this experiment?
Correct Answer: (a)
Went's experiment confirmed the presence of a diffusible chemical substance (which he named auxin) and allowed for its isolation.
Q70. Which one of the following pairs, is not correctly matched?
Correct Answer: (a)
Gibberellic acid is not associated with leaf fall; it promotes growth. ABA causes stomatal closure. IAA causes elongation. Cytokinins mainly cause division but also expansion. The mismatch is GA and Leaf fall.
Q71. One set of a plant was grown at 12 hours day and 12 hours night cycles and it flowered while in the other set night phase was interrupted by flash of light and it did not produce flower. Under which one of the following categories will you place this plant?
Correct Answer: (d)
Short-day plants require uninterrupted long night for flowering; interruption prevents flowering.
Q72. Typical growth curve in plants is :
Correct Answer: (d)
The growth curve in plants is sigmoid or S-shaped. It consists of three phases: Lag phase, Log phase and Stationary phase.
Q73. Treatment of seed at low temperature under moist conditions to break its dormancy is called
Correct Answer: (c)
Stratification is cold treatment to break seed dormancy. Vernalization is cold treatment to induce flowering.
Q74. Coiling of garden pea tendrils around any support is an example of:
Correct Answer: (c)
Thigmotropism is directional growth movement of curvature which occurs in response to stimulus of contact. It is seen in tendrils and twiners.
Q75. Klinostat is employed in the study of
Correct Answer: (b)
Klinostat is an apparatus used to negate the effect of gravity, thus employed in studying geotropism (a growth movement).
Q76. Thigmotropic movement is best shown by
Correct Answer: (a)
Tendrils show thigmotropism (directional growth in response to touch).
Q77. Importance of day length in flowering of plants was first shown in
Correct Answer: (b)
Tobacco.
Q78. Dwarfness can be controlled by treating the plant with
Q79. Through their effect on plant growth regulators, what do the temperature and light control in the plants?
Correct Answer: (b)
Light (photoperiod) and temperature (vernalization) control flowering.
Q80. Phototropic curvature is the result of uneven distribution of:
Correct Answer: (d)
Phototropism is due to uneven distribution of auxin.
Q81. ABA is involved in
Correct Answer: (a)
ABA induces seed dormancy.
Q82. Photoperiodism was first characterised in:
Correct Answer: (a)
Garner and Allard discovered photoperiodism in 'Maryland Mammoth' tobacco.
Q83. An enzyme that can stimulate germination of barley seeds is
Correct Answer: (d)
Gibberellin induces synthesis of α-amylase in barley seeds.
Q84. Which one of the following growth regulators is known as ‘stress hormone’?
Correct Answer: (a)
ABA is called stress hormone because it helps plants cope with stress conditions (e.g., closing stomata during drought).
Q85. Cell elongation in internodal regions of the green plants takes place due to
Correct Answer: (c)
Gibberellins cause internodal elongation (bolting).
Q86. If a tree, flowers thrice in a year (Oct., Jan. and July) in Northern India, it is said to be
Correct Answer: (d)
If a plant flowers thrice a year in different seasons (different temperatures and photoperiods), it is insensitive to both photo (light duration) and thermo (temperature) for flowering.
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