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Root-Shoot Balance
MCQ questions and answers.
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MCQ Questions
1. What is the general effect of a relatively high cytokinin level on the balance between roots and shoots in a plant?
A.
It favors shoot growth
B.
It completely stops shoot growth
C.
It favors only root hair formation
D.
It prevents cell division in shoots
Correct Answer:
It favors shoot growth
Explanation:
A relatively high cytokinin level promotes cell division and shoot development, thereby favoring shoot growth in the root-shoot balance.
2. In tissue culture, which hormonal condition generally favors root formation?
A.
Higher cytokinin concentration than auxin
B.
Higher auxin concentration than cytokinin
C.
Absence of both auxin and cytokinin
D.
Only a high cytokinin concentration
Correct Answer:
Higher auxin concentration than cytokinin
Explanation:
A higher auxin-to-cytokinin ratio generally favors root formation, whereas a higher cytokinin-to-auxin ratio favors shoots.
3. Which hormonal ratio generally promotes shoot formation in plant tissue culture?
A.
High cytokinin-to-auxin ratio
B.
High auxin-to-cytokinin ratio
C.
Equal absence of both hormones
D.
Very low levels of both hormones only
Correct Answer:
High cytokinin-to-auxin ratio
Explanation:
A high cytokinin-to-auxin ratio promotes shoot development and helps shift the balance away from root formation.
4. Cytokinin helps maintain root-shoot balance mainly by promoting which process?
A.
Cell division in shoots
B.
Water loss from roots
C.
Destruction of shoot cells
D.
Complete inhibition of root and shoot growth
Correct Answer:
Cell division in shoots
Explanation:
Cytokinins stimulate cell division, especially in developing shoots, and therefore influence the balance between shoot and root growth.
5. If a culture medium contains more cytokinin than auxin, which structure is most likely to develop?
A.
Shoots
B.
Roots only
C.
Mature seeds only
D.
Root caps only
Correct Answer:
Shoots
Explanation:
A medium with a relatively greater amount of cytokinin generally favors shoot formation over root formation.
6. What is likely to happen when cytokinin concentration is increased relative to auxin concentration in a plant culture?
A.
Shoot formation is favored
B.
Root formation is always favored
C.
Both roots and shoots immediately die
D.
Cell division stops completely
Correct Answer:
Shoot formation is favored
Explanation:
Increasing cytokinin relative to auxin shifts the developmental balance toward shoot formation.
7. Which combination is most suitable for producing roots from plant tissue in culture?
A.
Low cytokinin and relatively high auxin
B.
High cytokinin and no auxin
C.
High cytokinin and relatively low auxin
D.
Only cytokinin with no nutrients
Correct Answer:
Low cytokinin and relatively high auxin
Explanation:
Root formation is generally promoted when auxin is relatively higher than cytokinin in the culture medium.
8. A high cytokinin-to-auxin ratio in a plant tissue culture usually results in which root-shoot response?
A.
More shoot development than root development
B.
More root development than shoot development
C.
No change in either roots or shoots
D.
Immediate seed germination only
Correct Answer:
More shoot development than root development
Explanation:
A high cytokinin-to-auxin ratio favors shoot development, so shoot growth becomes greater relative to root growth.
9. Which hormone is generally more effective than cytokinin in promoting root formation when present at a relatively higher level?
A.
Auxin
B.
Cytokinin
C.
Chlorophyll
D.
Ethylene only
Correct Answer:
Auxin
Explanation:
Auxin generally promotes root formation when its level is relatively high compared with cytokinin, helping regulate root-shoot balance.
10. Why are cytokinin and auxin levels adjusted together in plant tissue culture?
A.
To control whether roots or shoots develop
B.
To remove all nutrients from the medium
C.
To prevent every type of cell division
D.
To stop the formation of plant organs
Correct Answer:
To control whether roots or shoots develop
Explanation:
The relative amounts of cytokinin and auxin determine whether the culture mainly forms shoots or roots, allowing control of root-shoot balance.
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Root-Shoot Balance
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