1. What is the primary role of auxins in plants?
a) Promote cell elongation
b) Promote seed germination
c) Stimulate root growth
d) Inhibit leaf abscission
Answer: a) Promote cell elongation
Explanation: Auxins primarily stimulate cell elongation in plant growth, particularly in shoots and stems, and play a critical role in phototropism and gravitropism.
2. Which of the following is the major naturally occurring auxin?
a) Gibberellin
b) Indole-3-acetic acid (IAA)
c) Abscisic acid (ABA)
d) Cytokinin
Answer: b) Indole-3-acetic acid (IAA)
Explanation: Indole-3-acetic acid (IAA) is the primary natural auxin in plants that plays an essential role in regulating growth processes like elongation and cell division.
3. Which hormone is responsible for stimulating cell division in plant tissues?
a) Auxins
b) Cytokinins
c) Gibberellins
d) Ethylene
Answer: b) Cytokinins
Explanation: Cytokinins are plant hormones that stimulate cell division and influence various developmental processes, including leaf growth and shoot formation.
4. Which of the following is not a function of cytokinins?
a) Stimulate shoot formation
b) Delay leaf senescence
c) Inhibit root growth
d) Promote cell division
Answer: c) Inhibit root growth
Explanation: Cytokinins promote shoot and cell growth, delay leaf senescence, and stimulate cell division. They generally do not inhibit root growth but may interact with auxins to regulate root development.
5. Which phytohormone is involved in fruit ripening?
a) Abscisic acid
b) Cytokinins
c) Ethylene
d) Gibberellins
Answer: c) Ethylene
Explanation: Ethylene is a gaseous hormone that regulates various processes, including fruit ripening, flower wilting, and leaf abscission.
6. Gibberellins are mainly involved in which of the following?
a) Inhibition of seed germination
b) Stem elongation
c) Leaf abscission
d) Fruit ripening
Answer: b) Stem elongation
Explanation: Gibberellins promote stem elongation, seed germination, and flowering, especially in plants that require long days or specific conditions for flowering.
7. What is the primary effect of abscisic acid in plants?
a) Promote seed germination
b) Stimulate root growth
c) Induce dormancy in seeds
d) Promote flowering
Answer: c) Induce dormancy in seeds
Explanation: Abscisic acid (ABA) primarily induces dormancy in seeds, prevents germination under unfavorable conditions, and helps plants respond to stress, such as drought.
8. Which hormone is known to inhibit growth in plants during stress conditions?
a) Gibberellins
b) Abscisic acid
c) Cytokinins
d) Auxins
Answer: b) Abscisic acid
Explanation: Abscisic acid is known to inhibit growth and promote stress responses, such as stomatal closure during drought conditions.
9. Auxin concentrations in plant cells are higher on the side that is:
a) Exposed to light
b) Opposite the light source
c) Near the roots
d) Near the stem apex
Answer: b) Opposite the light source
Explanation: Auxin accumulates on the shaded side of a plant stem in response to light, which promotes cell elongation on that side, causing the plant to bend towards the light (phototropism).
10. Which of the following hormones is responsible for apical dominance?
a) Gibberellins
b) Auxins
c) Cytokinins
d) Ethylene
Answer: b) Auxins
Explanation: Auxins are responsible for apical dominance, where the main shoot grows more vigorously than lateral buds, inhibiting their growth.
11. Which hormone promotes the elongation of the plant’s internodes?
a) Cytokinins
b) Gibberellins
c) Ethylene
d) Abscisic acid
Answer: b) Gibberellins
Explanation: Gibberellins promote internode elongation, resulting in taller plants. They also play a role in seed germination and flowering.
12. Which plant hormone is commonly used in agriculture to promote fruit set?
a) Cytokinins
b) Ethylene
c) Auxins
d) Gibberellins
Answer: c) Auxins
Explanation: Auxins are often used in agriculture to promote fruit set, particularly in seedless varieties, by stimulating the growth of ovary tissues into fruit.
13. Cytokinins are produced in which part of the plant?
a) Roots
b) Leaves
c) Flowers
d) All of the above
Answer: a) Roots
Explanation: Cytokinins are primarily produced in the roots and are transported to other parts of the plant, where they promote cell division and bud formation.
14. Which of the following statements about auxins is correct?
a) They stimulate fruit ripening.
b) They are involved in the elongation of root cells.
c) They inhibit the growth of lateral buds.
d) They are produced only in leaves.
Answer: c) They inhibit the growth of lateral buds.
Explanation: Auxins are involved in promoting cell elongation and inhibiting the growth of lateral buds, thereby maintaining apical dominance.
15. Which of the following hormones helps in seed dormancy release?
a) Cytokinins
b) Abscisic acid
c) Ethylene
d) Gibberellins
Answer: d) Gibberellins
Explanation: Gibberellins promote seed germination and are used to break seed dormancy in many plants.
16. What is the role of ethylene in plant aging?
a) It accelerates plant growth.
b) It delays leaf senescence.
c) It promotes fruit ripening and leaf abscission.
d) It inhibits cell division.
Answer: c) It promotes fruit ripening and leaf abscission.
Explanation: Ethylene is a gaseous hormone that promotes the aging of plants by initiating fruit ripening and the shedding of leaves.
17. Which of the following best describes a synergistic effect between auxins and cytokinins?
a) They both promote root growth.
b) They both promote stem elongation.
c) They work together to stimulate cell division and shoot growth.
d) They work together to induce dormancy.
Answer: c) They work together to stimulate cell division and shoot growth.
Explanation: Auxins and cytokinins often work together to promote cell division and stimulate shoot and bud growth.
18. Which hormone primarily controls leaf abscission?
a) Cytokinins
b) Ethylene
c) Abscisic acid
d) Gibberellins
Answer: b) Ethylene
Explanation: Ethylene is responsible for leaf abscission, the process by which leaves detach from the plant during senescence or in response to environmental factors.
19. Which plant hormone promotes the development of lateral roots?
a) Gibberellins
b) Cytokinins
c) Auxins
d) Ethylene
Answer: c) Auxins
Explanation: Auxins are responsible for stimulating the development of lateral roots, especially in response to environmental cues.
20. The presence of which hormone can accelerate the process of fruit ripening in bananas?
a) Abscisic acid
b) Cytokinins
c) Gibberellins
d) Ethylene
Answer: d) Ethylene
Explanation: Ethylene is the hormone that accelerates the process of fruit ripening in various fruits, including bananas.
21. Which of the following is a typical effect of gibberellins in plants?
a) Inhibition of seed germination
b) Promotion of shoot elongation
c) Induction of dormancy
d) Promotion of abscission
Answer: b) Promotion of shoot elongation
Explanation: Gibberellins primarily promote shoot elongation and also help in seed germination and flowering in some plants.
22. How do cytokinins affect plant aging?
a) They delay senescence and promote leaf retention.
b) They accelerate senescence.
c) They promote root growth.
d) They cause seed dormancy.
Answer: a) They delay senescence and promote leaf retention.
Explanation: Cytokinins delay senescence by promoting cell division and the retention of leaves, which helps in the continued growth of the plant.
23. Which plant hormone is involved in the closure of stomata during drought stress?
a) Cytokinins
b) Abscisic acid
c) Gibberellins
d) Auxins
Answer: b) Abscisic acid
Explanation: Abscisic acid (ABA) helps in the closure of stomata during water stress, preventing excessive water loss and conserving moisture in plants.
24. Which of the following hormones is involved in promoting leaf and fruit drop?
a) Cytokinins
b) Ethylene
c) Gibberellins
d) Auxins
Answer: b) Ethylene
Explanation: Ethylene plays a major role in the process of leaf and fruit abscission (drop) and in promoting fruit ripening.
25. Which hormone is used to promote the development of seedless fruits?
a) Abscisic acid
b) Cytokinins
c) Gibberellins
d) Ethylene
Answer: c) Gibberellins
Explanation: Gibberellins are used to promote the development of seedless fruits, particularly in grapes and citrus.
26. What effect do high concentrations of auxins have on root development?
a) They stimulate root formation.
b) They inhibit root growth.
c) They have no effect on roots.
d) They promote leaf formation.
Answer: b) They inhibit root growth.
Explanation: High concentrations of auxins typically inhibit root growth and can cause the formation of abnormal root structures.
27. Which hormone plays a role in delaying leaf senescence during the growing season?
a) Cytokinins
b) Gibberellins
c) Ethylene
d) Auxins
Answer: a) Cytokinins
Explanation: Cytokinins delay leaf senescence and promote cell division, helping the plant maintain its foliage during the growing season.
28. Which of the following is a characteristic effect of gibberellins in dwarf plants?
a) They reduce stem elongation.
b) They increase flowering.
c) They promote normal stem elongation.
d) They inhibit seed germination.
Answer: c) They promote normal stem elongation.
Explanation: Gibberellins promote stem elongation, and they are often used to restore normal growth in dwarf plants.
29. Which hormone causes an increase in seed germination rate?
a) Gibberellins
b) Abscisic acid
c) Cytokinins
d) Auxins
Answer: a) Gibberellins
Explanation: Gibberellins promote the rapid germination of seeds by stimulating the enzymes necessary for breaking down stored food during germination.
30. Which hormone is involved in promoting the lateral branching of plants?
a) Cytokinins
b) Gibberellins
c) Abscisic acid
d) Auxins
Answer: a) Cytokinins
Explanation: Cytokinins promote lateral branching in plants, helping to increase the growth of side shoots and creating a bushier plant.
These questions and answers provide a detailed overview of the various plant hormones, their roles, and their effects on plant growth and development.
