- Which of the following hormones is mainly responsible for the elongation of internodes in plants?
a) Cytokinin
b) Gibberellin
c) Abscisic acid
d) Auxin
Answer: b) Gibberellin
Explanation:
Gibberellins promote internodal elongation by stimulating cell elongation and division, which leads to taller plants with longer stems.
- The role of cytokinin in plant tissue culture is to:
a) Promote root formation
b) Promote shoot formation
c) Inhibit cell division
d) Induce dormancy
Answer: b) Promote shoot formation
Explanation:
In plant tissue culture, cytokinins are used to promote shoot formation by stimulating cell division and shoot bud differentiation.
- Which of the following is a short-day plant?
a) Wheat
b) Tobacco
c) Potato
d) Radish
Answer: b) Tobacco
Explanation:
Tobacco is a short-day plant that requires shorter daylight hours to initiate flowering. Such plants bloom when the length of the day is shorter than a critical duration.
- Which hormone is commonly used to break seed dormancy and promote germination?
a) Abscisic acid
b) Cytokinin
c) Gibberellin
d) Auxin
Answer: c) Gibberellin
Explanation:
Gibberellins promote seed germination by breaking seed dormancy and stimulating the production of enzymes that break down stored food in seeds.
- Which of the following is a climactic response in plants?
a) Vernalization
b) Thigmotropism
c) Hydrotropism
d) Gravitropism
Answer: b) Thigmotropism
Explanation:
Thigmotropism is the directional growth response of plants to touch stimuli, as seen in tendrils of climbing plants that wrap around structures for support.
- Which hormone is involved in closing stomata during water stress in plants?
a) Auxin
b) Abscisic acid
c) Gibberellin
d) Ethylene
Answer: b) Abscisic acid
Explanation:
Abscisic acid (ABA) helps close the stomata during water stress, preventing water loss through transpiration and conserving water within the plant.
- What is the major role of ethylene in fruit physiology?
a) Inhibit ripening
b) Promote fruit ripening
c) Stimulate seed dormancy
d) Delay senescence
Answer: b) Promote fruit ripening
Explanation:
Ethylene is a gaseous hormone that promotes the ripening of fruits by regulating various physiological processes, including the breakdown of cell walls and the conversion of starches to sugars.
- Which of the following factors can break seed dormancy?
a) Light exposure
b) High temperature
c) Gibberellins
d) Abscisic acid
Answer: c) Gibberellins
Explanation:
Gibberellins can break seed dormancy by promoting the synthesis of enzymes that degrade stored food reserves, providing energy for the seedling’s growth.
- Which of the following is not an effect of abscisic acid?
a) Inducing dormancy
b) Promoting senescence
c) Promoting stomatal closure
d) Stimulating seed germination
Answer: d) Stimulating seed germination
Explanation:
Abscisic acid inhibits seed germination and promotes seed dormancy, particularly during unfavorable conditions. It does not stimulate germination.
- Which plant hormone is known to cause apical dominance, inhibiting the growth of lateral buds?
a) Gibberellin
b) Cytokinin
c) Auxin
d) Abscisic acid
Answer: c) Auxin
Explanation:
Auxin maintains apical dominance by inhibiting the growth of lateral buds, allowing the apical bud to grow more vigorously and dominate the plant’s growth pattern.
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