NEET Biology: Growth regulators-auxin Practice Questions
12 free multiple-choice questions on Growth regulators-auxin (Plant Growth and Development) for NEET Biology, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.
Practice thousands more NEET questions in the app →Q1. If the concentration of auxin applied to a shoot is significantly increased, what is the expected immediate effect on the shoot?
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Correct answer: C — Faster stem elongation
Increased auxin concentration in the shoot leads to enhanced cell elongation, thus promoting faster stem growth.
Q2. The mechanism by which auxin controls differential growth rates between two adjacent cells is based on its interaction with which cellular process?
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Correct answer: D — Cell wall extensibility
Auxin influences the loosening of the cell wall components, thereby affecting the extensibility of the cell and its subsequent elongation.
Q3. Gravitropism (growth response in response to gravity) in plants is mediated by the redistribution of which hormone?
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Correct answer: C — Auxin
Gravity causes auxin to redistribute; auxin accumulates on the lower side of the shoot, leading to differential growth and bending in response to gravity.
Q4. Phototropism (the bending of a plant towards light) is primarily controlled by the differential distribution of which hormone?
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Correct answer: B — Auxin
Auxin migrates to the shaded side of the stem, causing differential growth and bending towards the light source (phototropism).
Q5. Auxin levels are generally highest in which region of a plant stem?
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Correct answer: D — Shoot apex
Auxin is synthesized primarily at the shoot apex and then moves down the stem, leading to higher concentrations near the apex during synthesis.
Q6. The primary role of auxin in regulating plant growth is to affect the rate of:
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Correct answer: C — Cell division and elongation
Auxin directly influences the process of cell elongation and differentiation, which are fundamental aspects of plant growth.
Q7. The main site of auxin synthesis in a plant is the region known as:
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Correct answer: C — Shoot apical meristem
Auxin is primarily synthesized by the cells of the shoot apical meristem (SAM), which is the region responsible for shoot growth.
Q8. Auxin is generally synthesized at the shoot apex and transported to the rest of the plant. What is the general direction of auxin movement in a typical stem?
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Correct answer: D — Downward
Auxin is synthesized at the shoot and moves downwards throughout the stem and roots.
Q9. When auxin concentration is high in the shoot tip, it causes a differential growth pattern in the stem, which is the underlying mechanism for which phenomenon?
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Correct answer: D — apical dominance
High auxin concentration in the shoot tip leads to apical dominance, where the shoot grows preferentially, suppressing the growth of lateral buds.
Q10. Which of the following is the primary growth regulator in plants?
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Correct answer: A — Auxin
Auxin (IAA) is the most important plant hormone responsible for regulating growth and development in plants.
Q11. Which hormonal action is primarily responsible for promoting cell division in the apical meristem?
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Correct answer: C — Cytokinins
Cytokinins are crucial growth regulators that promote cell division (cytokinesis) in meristematic tissues.
Q12. Deficiency of auxin in a plant generally leads to which of the following effects?
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Correct answer: C — Reduced growth
Since auxin is the primary growth regulator, its deficiency results in impaired growth and reduced cell elongation.
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