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Plant Growth and Development

Apical Dominance and Gravitropism Practice Questions

20 free Apical Dominance and Gravitropism practice questions for the NCERT Biology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.

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Question 1 of 20 Medium

Apical dominance in plants is primarily regulated by which plant hormone?

  1. A Cytokinin
  2. B Auxin (IAA)
  3. C Gibberellin
  4. D Ethylene

Correct answer: Auxin (IAA)

Auxin (specifically IAA) is produced at the apical bud and suppresses the growth of lateral buds. This hormonal control maintains apical dominance in plants.

Question 2 of 20 Medium

Removal of the apical bud in a shoot generally results in:

  1. A Inhibition of lateral bud growth
  2. B Enhanced elongation of the main stem
  3. C Activation of lateral buds to branch
  4. D Complete cessation of growth

Correct answer: Activation of lateral buds to branch

Removing the apical bud reduces auxin concentration in the stem. This allows lateral buds to grow and results in branching.

Question 3 of 20 Medium

Which hormone can counteract apical dominance when applied to lateral buds?

  1. A Auxin
  2. B Abscisic acid
  3. C Cytokinin
  4. D Ethylene

Correct answer: Cytokinin

Cytokinins promote cell division and stimulate lateral bud growth. They can overcome the inhibitory effect of auxin on lateral buds.

Question 4 of 20 Medium

Gravitropism refers to the growth response of plants to:

  1. A Sunlight
  2. B Water
  3. C Gravity
  4. D Touch

Correct answer: Gravity

Gravitropism is the directional growth of plant parts in response to gravity. Roots and shoots show opposite responses to this stimulus.

Question 5 of 20 Medium

Roots usually exhibit which type of gravitropic response?

  1. A Positive gravitropism
  2. B Negative gravitropism
  3. C Neutral gravitropism
  4. D Diagravitropism

Correct answer: Positive gravitropism

Roots grow in the direction of gravitational pull. This response is termed positive gravitropism.

Question 6 of 20 Medium

Shoots show negative gravitropism because they grow:

  1. A Towards gravity
  2. B Away from gravity
  3. C Parallel to gravity
  4. D Independently of gravity

Correct answer: Away from gravity

Shoots grow upward, opposite to the direction of gravity. This growth pattern is called negative gravitropism.

Question 7 of 20 Medium

Which cells in the root tip are mainly involved in gravity perception?

  1. A Root hair cells
  2. B Meristematic cells
  3. C Elongation zone cells
  4. D Columella cells with statoliths

Correct answer: Columella cells with statoliths

Columella cells contain statoliths that settle under gravity. This helps the root perceive the direction of gravitational pull.

Question 8 of 20 Medium

Statoliths involved in gravitropism are composed mainly of:

  1. A Structural proteins
  2. B Starch-filled amyloplasts
  3. C Lipid droplets
  4. D Cellulose microfibrils

Correct answer: Starch-filled amyloplasts

Statoliths are dense starch-filled plastids (amyloplasts). Their movement within cells helps plants sense gravity.

Question 9 of 20 Medium

In roots, higher auxin concentration on the lower side causes:

  1. A Increased cell elongation
  2. B No change in growth
  3. C Inhibition of cell elongation
  4. D Cell division without elongation

Correct answer: Inhibition of cell elongation

High auxin concentration inhibits cell elongation in roots. This causes the root to bend downward toward gravity.

Question 10 of 20 Medium

In shoots, higher auxin concentration on the lower side leads to:

  1. A Reduced growth
  2. B Enhanced cell elongation
  3. C Cell death
  4. D Inhibition of auxin transport

Correct answer: Enhanced cell elongation

Auxin promotes cell elongation in shoots. Accumulation on the lower side causes faster growth, bending the shoot upward.

Question 11 of 20 Medium

Which experiment demonstrated the role of auxin in apical dominance?

  1. A Darwin’s phototropism experiment
  2. B Boysen-Jensen’s experiment
  3. C Went’s agar block experiment
  4. D Miller and Urey experiment

Correct answer: Went’s agar block experiment

Went’s agar block experiment showed that a chemical substance from the tip promotes growth. This substance was later identified as auxin.

Question 12 of 20 Medium

The redistribution of auxin during gravitropism occurs mainly through:

  1. A Xylem transport
  2. B Phloem transport
  3. C Polar transport
  4. D Diffusion only

Correct answer: Polar transport

Auxin is transported directionally by polar transport. This redistribution creates differential growth during gravitropic responses.

Question 13 of 20 Medium

Which part of the plant is most sensitive to gravity?

  1. A Leaf blade lamina
  2. B Root cap region
  3. C Stem internode
  4. D Mature stem tissue

Correct answer: Root cap region

The root cap is highly sensitive to gravity. It contains specialized columella cells that perceive gravitational signals.

Question 14 of 20 Medium

Apical dominance is ecologically advantageous because it:

  1. A Increases root branching depth
  2. B Reduces water loss by transpiration
  3. C Promotes upward growth for light
  4. D Permanently stops all lateral growth

Correct answer: Promotes upward growth for light

Apical dominance helps plants grow taller and access more light. This provides a competitive advantage in dense vegetation.

Question 15 of 20 Medium

Which of the following conditions would reduce apical dominance?

  1. A High auxin at the apex
  2. B Cytokinin applied to lateral buds
  3. C Intact and active apical bud
  4. D Active polar auxin transport

Correct answer: Cytokinin applied to lateral buds

Cytokinins stimulate lateral bud growth and oppose auxin action. Their application reduces apical dominance.

Question 16 of 20 Medium

Gravitropic curvature in roots mainly occurs due to differential growth in which zone?

  1. A Root cap
  2. B Meristematic zone
  3. C Zone of elongation
  4. D Zone of differentiation

Correct answer: Zone of elongation

The bending response in roots occurs in the zone of elongation. Differential cell elongation causes curvature.

Question 17 of 20 Medium

Which statement about auxin action is correct?

  1. A Grow straight without any bending
  2. B Show phototropism response only
  3. C Bend upward by gravitropism
  4. D Stop all growth activity

Correct answer: Bend upward by gravitropism

Even in the absence of light, gravity influences growth direction. The shoot bends upward due to negative gravitropism.

Question 18 of 20 Medium

If a horizontally placed shoot is kept in darkness, it will:

  1. A Grow straight without bending
  2. B Show phototropism only
  3. C Bend upward due to gravitropism
  4. D Stop growing

Correct answer: Bend upward due to gravitropism

Even in the absence of light, gravity influences growth direction. The shoot bends upward due to negative gravitropism.

Question 19 of 20 Medium

Which factor primarily differentiates phototropism from gravitropism?

  1. A Type of hormone involved
  2. B Nature of the triggering stimulus
  3. C Site of signal perception
  4. D Growth zone that responds

Correct answer: Nature of the triggering stimulus

Phototropism is a response to light, while gravitropism is a response to gravity. The stimulus differentiates the two processes.

Question 20 of 20 Medium

The suppression of lateral buds by apical dominance occurs because auxin:

  1. A Stimulates cytokinin synthesis in buds
  2. B Directly destroys lateral bud tissue
  3. C Blocks cytokinin action in lateral buds
  4. D Halts photosynthesis in lateral buds

Correct answer: Blocks cytokinin action in lateral buds

Auxin suppresses the growth-promoting effect of cytokinins in lateral buds. This inhibition maintains apical dominance.

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