- Which of the following is an example of a long-day plant?
a) Tomato
b) Rice
c) Wheat
d) Sunflower
Answer: c) Wheat
Explanation:
Long-day plants, like wheat, flower when they are exposed to longer daylight hours, typically more than 12 hours a day. These plants are often found in regions where the days are longer during certain seasons.
- Which of the following plant hormones induces the formation of adventitious roots in cuttings?
a) Gibberellin
b) Ethylene
c) Cytokinin
d) Auxin
Answer: d) Auxin
Explanation:
Auxins promote the formation of adventitious roots in cuttings by stimulating cell division and elongation. This property of auxins is widely used in plant propagation through cuttings.
- Which process describes the falling off of leaves, flowers, or fruits from a plant?
a) Apical dominance
b) Abscission
c) Bolting
d) Photoperiodism
Answer: b) Abscission
Explanation:
Abscission is the process in which plants shed leaves, flowers, or fruits. Ethylene promotes abscission by weakening the cells at the abscission zone, leading to the detachment of plant organs.
- Which of the following is a naturally occurring auxin?
a) NAA (Naphthalene acetic acid)
b) IBA (Indole-3-butyric acid)
c) 2,4-D (2,4-Dichlorophenoxyacetic acid)
d) IAA (Indole-3-acetic acid)
Answer: d) IAA (Indole-3-acetic acid)
Explanation:
IAA (Indole-3-acetic acid) is a naturally occurring auxin that plays a vital role in plant growth and development by regulating cell elongation, apical dominance, and root initiation.
- What is the primary role of gibberellins in plants?
a) Inhibits seed germination
b) Delays senescence
c) Promotes stem elongation
d) Closes stomata
Answer: c) Promotes stem elongation
Explanation:
Gibberellins promote cell elongation and division in the stems, leading to increased plant height. They are also involved in breaking seed dormancy and inducing flowering.
- Which of the following is an effect of cytokinins?
a) Promote root growth
b) Delay leaf senescence
c) Promote fruit ripening
d) Stimulate stem elongation
Answer: b) Delay leaf senescence
Explanation:
Cytokinins delay leaf senescence by promoting nutrient mobilization, thereby maintaining the green color and health of leaves for a longer period.
- Which of the following plant growth regulators is involved in seed dormancy and closing of stomata under water stress?
a) Auxin
b) Abscisic acid
c) Ethylene
d) Gibberellin
Answer: b) Abscisic acid
Explanation:
Abscisic acid (ABA) induces seed dormancy and plays a significant role in closing stomata during water stress, helping plants conserve water by reducing transpiration.
- Which of the following is responsible for the upward growth of shoots in plants?
a) Positive phototropism
b) Positive gravitropism
c) Negative gravitropism
d) Hydrotropism
Answer: c) Negative gravitropism
Explanation:
Negative gravitropism is the growth movement of shoots away from the force of gravity, causing them to grow upward. In contrast, roots show positive gravitropism as they grow towards gravity.
- Which plant hormone is known to promote flowering in pineapple and other plants?
a) Auxin
b) Gibberellin
c) Cytokinin
d) Ethylene
Answer: d) Ethylene
Explanation:
Ethylene promotes flowering in certain plants, such as pineapple. It is also involved in fruit ripening and leaf abscission.
- What is the role of cytokinins in plant growth?
a) Promote seed germination
b) Delay leaf senescence
c) Induce flowering
d) Promote fruit ripening
Answer: b) Delay leaf senescence
Explanation:
Cytokinins delay leaf senescence (aging) by promoting cell division and nutrient distribution, ensuring the leaves retain their green color and functionality for longer.
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