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.
Q2. Apical dominance is caused by
[1992]
Correct Answer: (d)
Auxin produced in the shoot tip suppresses lateral buds.
Q3. Ethylene gas is used for
[1995]
Correct Answer: (b)
Ethylene is used for fruit ripening.
Q4. Which one increases in the absence of light?
[1991]
Correct Answer: (c)
In darkness, etiolation causes elongation of internodes.
Q5. 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?
[2014]
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).
Q6. Which one of the following generally acts as an antagonist to gibberellins?
[2012M]
Correct Answer: (c)
ABA acts as an antagonist to Gibberellins (e.g., in seed dormancy vs germination).
Q7. Tendrils exhibit/twining of tendrils is due to
[1991]
Correct Answer: (a)
Thigmotropism is growth response to touch, seen in tendrils.
Q8. Which is employed for artificial ripening of banana fruits?
[1992, 2000]
Correct Answer: (c)
Ethylene is the fruit ripening hormone.
Q9. What causes a green plant exposed to the light on only one side, to bend toward the source of light as it grows ?
[2015 RS]
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. Dwarfness can be controlled by treating the plant with
[1992, 2002]
Q11. Flowering dependent on cold treatment is
[1992]
Correct Answer: (d)
Vernalisation is induction of flowering by low temperature treatment.
Q12. A plant hormone used for inducing morphogenesis in plant tissue culture is
[1998]
Correct Answer: (b)
Cytokinins (with Auxins) are used for morphogenesis (organogenesis).
Q13. Treatment of seed at low temperature under moist conditions to break its dormancy is called
[2006]
Correct Answer: (c)
Stratification is cold treatment to break seed dormancy. Vernalization is cold treatment to induce flowering.
Q14. 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?
[2004]
Correct Answer: (d)
Short-day plants require uninterrupted long night for flowering; interruption prevents flowering.
Q15. The regulator which retards ageing/senescence of plant parts is :
[1993]
Q16. Leaves of many grasses are capable of folding and unfolding because they
[1989]
Correct Answer: (c)
Bulliform cells in grasses allow leaves to roll up during water stress to reduce transpiration.
Q17. ABA is involved in
[1999]
Correct Answer: (a)
ABA induces seed dormancy.
Q18. Which one is a long-day plant?
[2001]
Correct Answer: (d)
Spinach is a long-day plant requiring longer photoperiod for flowering.
Q19. Differentiation of shoot is controlled by
[2003]
Correct Answer: (c)
High Cytokinin/Auxin ratio promotes shoot differentiation. High Auxin/Cytokinin promotes roots.
Q20. Which one of the following growth regulators is known as ‘stress hormone’?
[2014]
Correct Answer: (a)
ABA is called stress hormone because it helps plants cope with stress conditions (e.g., closing stomata during drought).
Q21. Photoperiodism was first characterised in:
[2010]
Correct Answer: (a)
Garner and Allard discovered photoperiodism in 'Maryland Mammoth' tobacco.
Q22. What breaks bud dormancy of potato tuber?
[2001]
Correct Answer: (a)
Gibberellins break dormancy.
Q23. What will be the effect on phytochrome in a plant subjected to continuous red light?
[1997]
Correct Answer: (d)
Under continuous red light, interconversion maintains equilibrium of phytochrome forms.
Q24. Abscisic acid causes
[1991]
Correct Answer: (a)
ABA induces stomatal closure under water stress.
Q25. Klinostat is employed in the study of
[1993]
Correct Answer: (b)
Klinostat is an apparatus used to negate the effect of gravity, thus employed in studying geotropism (a growth movement).
Q26. Seed dormancy is due to the
[2002]
Correct Answer: (b)
ABA induces seed dormancy.
Q27. Removal of apical bud results in
[1993, 2000]
Correct Answer: (d)
Removal of apical dominance promotes lateral branching.
Q28. Thigmotropic movement is best shown by
[1995]
Correct Answer: (a)
Tendrils show thigmotropism (directional growth in response to touch).
Q29. Which one of the following pairs, is not correctly matched?
[2007]
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.
Q30. Movement of leaves of Sensitive Plant, Mimosa pudica are due to
[1988, 99]
Correct Answer: (b)
The movement of leaves of Mimosa pudica (Touch-me-not) is due to seismonasty (response to shock/touch).
Q31. Importance of day length in flowering of plants was first shown in
[2008]
Correct Answer: (b)
Tobacco.
Q32. The response of different organisms to environmental rhythms of light and darkness is called
[1998]
Correct Answer: (b)
Photoperiodism is the response of organisms to day-length changes.
Q33. Cytokinins
[1992]
Correct Answer: (c)
Cytokinins delay senescence by retaining chlorophyll and nutrients.
Q34. Which of the following prevents fall of fruits?
[2001]
Correct Answer: (b)
NAA (Synthetic Auxin) prevents premature fruit drop.
Q35. Which combination of gases is suitable for fruit ripening?
[1998]
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.
Q36. Proteinaceous pigment which control activities concerned with light
[2001]
Correct Answer: (a)
Phytochrome is a proteinaceous pigment involved in light-regulated activities.
Q37. Fruit and leaf drop at early stages can be prevented by the application of:
[2017]
Correct Answer: (b)
Auxins prevent premature abscission of plant organs like leaves and fruits.
Q38. The method that renders the seed coat permeable to water so that embryo expansion is not physically retarded is
[2000]
Correct Answer: (d)
Scarification breaks or weakens the seed coat to allow water uptake.
Q39. An enzyme that can stimulate germination of barley seeds is
[2006]
Correct Answer: (d)
Gibberellin induces synthesis of α-amylase in barley seeds.
Q41. Removal of shoot tips is a very useful technique to boost the production of tealeaves. This is because :
[2019]
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.
Q42. Cut or excised leaves remain green for long if induced to root or dipped in
[1988]
Correct Answer: (b)
Cytokinins delay senescence (loss of chlorophyll).
Q43. In order to increase the yield of sugarcane crop, which of the following plant growth regulators should be sprayed?
[2019]
Correct Answer: (d)
Phytohormones are chemical substances produced naturally in plants that regulate growth and physiological processes.
Q45. If a tree, flowers thrice in a year (Oct., Jan. and July) in Northern India, it is said to be
[1997]
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.
Q46. Highest auxin concentration occurs
[1990]
Correct Answer: (a)
Auxin is synthesized in growing tips (apices).
Q47. Movement of auxin is
[1994]
Correct Answer: (b)
Auxin transport is polar, primarily basipetal in stems.
Q48. Auxetic growth is
[1994]
Correct Answer: (a)
Auxetic growth involves increase in cell size/volume without cell division.
Q49. Anthesis is a phenomenon which refers to
[2007]
Correct Answer: (d)
Anthesis is the period during which a flower is fully open and functional.
Q50. Bananas can be prevented from over-ripening by
[1992]
Correct Answer: (c)
Ascorbic acid is an antioxidant that can delay ripening/browning.
Q51. How does pruning help in making the hedge dense?
[2006]
Correct Answer: (a)
Pruning removes the apical bud (source of auxin), releasing axillary buds from apical dominance, leading to branching.
Q52. Auxin can be bioassayed by :
[2015 RS]
Correct Answer: (d)
Avena coleoptile curvature test is a bioassay for Auxins. Lettuce hypocotyl elongation is for Gibberellins.
Q53. Plants deficient of element zinc, show its effect on the biosynthesis of plant growth hormone
[2003]
Correct Answer: (b)
Zinc is required for the synthesis of Tryptophan, which is the precursor of Auxin (IAA).
Q54. Which one of the following acids is a derivative of carotenoids ?
[2009]
Correct Answer: (c)
Abscisic acid (ABA) is a derivative of carotenoids.
Q55. Phototropic curvature is the result of uneven distribution of:
[2010]
Correct Answer: (d)
Phototropism is due to uneven distribution of auxin.
Q56. What is the site of perception of photoperiod necessary for induction of flowering in plants ?
[2019]
Correct Answer: (d)
Leaves perceive the photoperiodic stimulus.
Q57. Coiling of garden pea tendrils around any support is an example of:
[2010]
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.
Q58. During seed germination its stored food is mobilized
[NEET 2013]
Correct Answer: (c)
Gibberellins stimulate the synthesis of hydrolytic enzymes (like alpha-amylase) to mobilize stored food during germination.
Q59. Hormone responsible for senescence
[2001]
Correct Answer: (a)
ABA promotes senescence.
Q60. Cell elongation in internodal regions of the green plants takes place due to
[2004]
Correct Answer: (c)
Gibberellins cause internodal elongation (bolting).
Q61. Mowing grass lawn facilitates better maintenance because
[1989]
Correct Answer: (b)
Removing tips removes apical dominance, allowing intercalary meristems (in grasses) and lateral buds to grow, making turf dense.
Q62. The Avena curvature is used for bioassay of
[2016]
Correct Answer: (c)
The Avena coleoptile curvature test is the bioassay for Auxin (IAA).
Q63. Through their effect on plant growth regulators, what do the temperature and light control in the plants?
[2012M]
Correct Answer: (b)
Light (photoperiod) and temperature (vernalization) control flowering.
Q64. “Foolish seedling” disease of rice led to the discovery of
[2007]
Correct Answer: (d)
Bakanae disease (Foolish seedling) caused by Gibberella fujikuroi led to discovery of Gibberellins (GA).
Q65. Vernalization stimulates flowering in
[2012M]
Correct Answer: (c)
Carrot is a biennial plant requiring vernalization for flowering.
Q66. Phototropic and geotropic movements are linked to :
[1990]
Correct Answer: (c)
Auxin distribution causes these tropisms.
Q67. One of the synthetic auxin is:
[2009]
Correct Answer: (d)
NAA (Naphthalene Acetic Acid) is a synthetic auxin. IAA and IBA are natural.
Q68. What is a stress hormone? or The hormone produced during adverse environmental conditions is
[1993]
Correct Answer: (d)
ABA is the stress hormone.
Q69. Abscisic acid controls
[1990]
Correct Answer: (b)
ABA promotes abscission (leaf fall) and dormancy.
Q70. A chemical believed to be involved in flowering is
[1991, 95]
Correct Answer: (c)
Florigen is the hypothetical flowering hormone.
Q71. The pine apple which under natural conditions is difficult to blossom has been made to produce fruits throughout the year by application of
[NEET Kar. 2013]
Correct Answer: (b)
Synthetic auxins like NAA and 2,4-D are used to induce flowering in pineapple.
Q72. Hormone primarily connected with cell division is
[1988, 1991]
Q73. Which of the following hormones can replace vernalisation?
[1989]
Correct Answer: (c)
Gibberellins can substitute cold treatment required for flowering.
Q74. What reason will you assign for coconut milk used in tissue culture?
[2000, 03]
Correct Answer: (b)
Coconut milk is rich in Cytokinins (Zeatin), promoting cell division.
Q75. Which of the following is not an inhibitory substance governing seed dormancy?
[2020]
Correct Answer: (d)
Gibberellic acid breaks seed dormancy and promotes germination. Others are inhibitors.
Q76. 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?
[2014]
Correct Answer: (a)
Went's experiment confirmed the presence of a diffusible chemical substance (which he named auxin) and allowed for its isolation.
Q77. The pigment, that absorbs red and far red light in plants, is
[1995, 97, 2002]
Correct Answer: (c)
Phytochrome absorbs red and far-red light and regulates photoperiodic responses.
Q78. Senescence as an active developmental cellular process in the growth and functioning of a flowering plant, is indicated in
[2008]
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.
Q79. 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?
[2019]
Correct Answer: (a)
Auxins (like NAA, 2,4-D) and Ethylene are used to induce flowering in pineapple.
Q80. Which of the following movement is not related to auxin level?
[1990]
Correct Answer: (c)
Nyctinastic movements are turgor movements (nastic), not growth movements regulated by auxin like tropisms.
Q81. In short-day plants, flowering is induced by
[1992]
Correct Answer: (b)
Short-day plants require uninterrupted long night below a critical photoperiod.
Q82. Name the plant growth regulator which upon spraying on sugarcane crop, increases the length of stem, thus increasing the yield of sugarcane crop.
[2020]
Correct Answer: (a)
Gibberellins increase the length of internodes in sugarcane stems, increasing yield.
Q83. Phytochrome is involved in
[1988]
Correct Answer: (c)
Phytochrome regulates photoperiodic responses in plants.
Q84. Leaf fall can be prevented with the help of
[1989]