- Which hormone is responsible for apical dominance in plants?
a) Ethylene
b) Gibberellins
c) Auxins
d) Abscisic acid
Answer: c) Auxins
Explanation:
Auxins produced in the apical meristem inhibit the growth of lateral buds, a phenomenon known as apical dominance. This ensures the plant grows taller rather than wider.
- Which type of movement is exhibited by plants in response to light?
a) Hydrotropism
b) Thigmotropism
c) Phototropism
d) Gravitropism
Answer: c) Phototropism
Explanation:
Phototropism is the growth movement of plants in response to light. Auxins accumulate on the shaded side of the plant, causing cell elongation and bending the plant towards the light.
- Which of the following hormones is responsible for the closing of stomata during water stress?
a) Abscisic acid
b) Cytokinins
c) Gibberellins
d) Ethylene
Answer: a) Abscisic acid
Explanation:
Abscisic acid (ABA) plays a key role in closing stomata during water stress to prevent excessive water loss through transpiration.
- The phenomenon of bolting in plants is induced by:
a) Ethylene
b) Gibberellins
c) Auxins
d) Cytokinins
Answer: b) Gibberellins
Explanation:
Bolting refers to the rapid elongation of the floral stalk, which is often induced by gibberellins, particularly in plants like cabbage and lettuce.
- Which of the following is an effect of cytokinins?
a) Delaying leaf senescence
b) Promoting fruit ripening
c) Inducing seed dormancy
d) Inhibiting stem elongation
Answer: a) Delaying leaf senescence
Explanation:
Cytokinins delay leaf senescence (aging) by promoting nutrient mobilization and helping maintain chlorophyll content, thereby prolonging the green life of the leaf.
- The maximum elongation in a plant cell occurs during which phase of growth?
a) Cell division phase
b) Maturation phase
c) Cell enlargement phase
d) Differentiation phase
Answer: c) Cell enlargement phase
Explanation:
During the cell enlargement phase, cells increase in size due to the uptake of water, which leads to cell elongation. This phase follows the cell division phase in the growth process.
- Which of the following is a synthetic auxin?
a) NAA (Naphthalene acetic acid)
b) IAA (Indole-3-acetic acid)
c) GA3 (Gibberellic acid)
d) Zeatin
Answer: a) NAA (Naphthalene acetic acid)
Explanation:
NAA (Naphthalene acetic acid) is a synthetic auxin that is used in agriculture to promote root initiation in cuttings and tissue culture.
- In which of the following plants is photoperiodism most evident?
a) Mango
b) Wheat
c) Tomato
d) Rice
Answer: b) Wheat
Explanation:
Wheat is a long-day plant, meaning it requires longer daylight hours to induce flowering. Photoperiodism is the response of plants to the length of day and night.
- What is the name of the process by which a seed becomes dormant?
a) Imbibition
b) Stratification
c) Quiescence
d) Vernalization
Answer: c) Quiescence
Explanation:
Quiescence refers to a state of dormancy where the seed is viable but does not germinate due to unfavorable environmental conditions, such as lack of water or appropriate temperature.
- What is the function of the hormone gibberellin in seed germination?
a) It breaks down starch into sugar.
b) It closes stomata to prevent water loss.
c) It delays the aging of leaves.
d) It inhibits seed germination.
Answer: a) It breaks down starch into sugar.
Explanation:
Gibberellins promote the synthesis of the enzyme amylase, which breaks down stored starch into sugars, providing energy for the growth of the embryo during seed germination.
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