Free Plant Growth Regulators MCQs with Answers
47 Plant Growth Regulators MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Plant growth regulators are chemical messengers that control growth, development and responses to the environment. The topic covers auxins, gibberellins, cytokinins, abscisic acid and ethylene, including cell elongation, apical dominance, tropisms, seed germination, dormancy, fruit ripening and leaf fall, with growth promoters distinguished from inhibitors.
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- A. I only
- B. II only
- C. I and II
- D. II and III
Explanation: The correct answer is D. II and III. Both auxin and cytokinin are hormones synthesized in meristematic tissues of plants.
Correct answer: II and III- A. Epinasty
- B. Nutation
- C. Hyponasty
- D. Nyctinasty
Explanation: Nutation is a type of growth movement where a plant part, such as a stem or tendril, exhibits revolving or spiraling motion.
Correct answer: Nutation- A. Delay both bud initiation and leaf senescence
- B. Promote both bud initiation and leaf senescence
- C. Promote bud initiation and delay leaf senescence
- D. Promote leaf senescence and delay bud initiation
Explanation: The correct answer is that auxins and gibberellins promote bud initiation and delay leaf senescence.
Correct answer: Promote bud initiation and delay leaf senescence- A. Ethene and Auxin
- B. Auxin and Gibberellin
- C. Abscisic acid and Ethene
- D. Gibberellin and Abscisic acid
Explanation: The correct answer is Option B: auxin and gibberellin. These two hormones are known to promote plant growth by stimulating cell elongation…
Correct answer: Auxin and Gibberellin- A. Vernalization
- B. Seed dormancy
- C. Photoperiodism
- D. Seed germination
Explanation: The correct answer is Vernalization . Vernalization is a process in which the prolonged exposure to cold temperatures triggers the…
Correct answer: Vernalization- A. Red light enhances cell division, blue light promotes cell elongation
- B. Red light promotes cell elongation, blue light enhances cell division
- C. Red light enhances cell division, blue light retards cell enlargement
- D. Red light promotes cell elongation, blue light retards cell division
Explanation: The correct answer is that red light enhances cell division, and blue light promotes cell elongation.
Correct answer: Red light enhances cell division, blue light promotes cell elongation- A. Bark
- B. Leaves
- C. Lateral shoots
- D. Vascular cambium
Explanation: Leaf Primordia: These are young leaf tissues that form on the flanks of the SAM and will develop into mature leaves.
Correct answer: Leaves- A. lower half of the root and stimulates growth.
- B. lower half of the root and slows down the growth.
- C. upper half of the root and slows down the growth.
- D. Upper half of the root and stimulates growth
Explanation: In a root placed horizontally, the bottom side contains more auxin and grows less, causing the root to move away from light.
Correct answer: lower half of the root and slows down the growth.- A. Auxin
- B. Gibberellin
- C. Cytokinin
- D. Ethene
Explanation: Gibberellin is the correct answer because it is a plant hormone that plays a critical role in the ripening process of fruits.
Correct answer: Gibberellin- A. Keeping the plant warm during the night-time
- B. Exposing the plant to a light source during the night
- C. Covering the plant with a black cloth for 12 hours a day
- D. Covering the plant with a transparent plastic during the daytime
Explanation: Long-day plants require a certain length of daylight to trigger flowering.
Correct answer: Exposing the plant to a light source during the night- A. Exposing the seeds to heat
- B. Treating the seed coats with acid
- C. Keeping the seed coats hard and dry
- D. Giving low temperature treatment to seeds
Explanation: The only option that does not break dormancy is keeping the seed coats hard and dry, hence option C is correct.To break seed dormancy…
Correct answer: Keeping the seed coats hard and dry- A. I only
- B. I and II
- C. III only
- D. II and III
Explanation: Only option I and II are correct as In many biennials (e.g., carrot, beet) and some perennials, the shoot apical meristem is the site…
Correct answer: I and II- A. A
- B. B
- C. C
- D. D
Explanation: Only option B shows positive geotropism as pea seedling growing in a porous pot and sand, with roots growing downwards demonstrates…
Correct answer: B- A. Auxin
- B. Ethylene
- C. Cytokinin
- D. Gibberellin
Explanation: The correct answer is Option B, also known as ethylene, is a plant hormone that is crucial in the ripening of fruits.
Correct answer: Ethylene- A. Are devoid of all kinds of nutrients
- B. Could produce fruits with hard fruit wall
- C. Require a period of rest before germination
- D. Could produce plants that are vulnerable to diseases
Explanation: The correct answer is that seeds require a period of rest before germination (Option C).
Correct answer: Require a period of rest before germination- A. Root apex
- B. Shoot apex
- C. Base of internodes
- D. Lateral sides of shoots
Explanation: Intercalary meristems are primarily found at the base of internodes in many plants and are responsible for the elongation of plant…
Correct answer: Base of internodes- A. Auxins.
- B. Gibberellins.
- C. Abscisic acid.
- D. Ethane.
Explanation: Gibberellins promote leaf and fruit growths.
Correct answer: Gibberellins.- A. Nastic.
- B. Growth.
- C. Turgor.
- D. Tactic.
Explanation: Nastic movements are a type of paratonic movement.
Correct answer: Nastic.- A. Synchronizes.
- B. Promotes.
- C. Inhibits.
- D. Does not affect.
Explanation: It has been found that red light Inhibits flowering the short day plants but promotes flowering in long day plants.
Correct answer: Promotes.- A. Enhancement of cell differentiation
- B. Maturation of the cells
- C. Elongation of cells
- D. Enhancement of cell division
Explanation: Explanation:Red light favours elongation of cells and blue light enhances cell division but retards cell enlargement.When red light can…
Correct answer: Elongation of cellsPlant Growth Regulators MCQs: common questions
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