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Quiz Chapter 2: Leaf Structure and Function

10 questions · Form 5 Biology Bab 2: Leaf Structure and Function

10 questions · plays in fullscreen

Full Question List & Answer Key

Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.

1. Which leaf tissue layer contains the highest density of chloroplasts specialized for maximum sunlight absorption?

  1. Spongy mesophyll
  2. Palisade mesophyll
  3. Upper epidermis
  4. Vascular bundle
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Answer: B

Palisade mesophyll cells are vertically elongated, closely packed, and packed with chloroplasts to maximize photosynthetic light capture.

2. How does an increase in wind speed affect the rate of transpiration in a terrestrial plant?

  1. Decreases transpiration by increasing atmospheric humidity near stomata.
  2. Increases transpiration by sweeping away accumulated water vapor surrounding stomata.
  3. Completely stops transpiration by triggering immediate stomatal closure.
  4. Has zero impact on the diffusion gradient of water vapor.
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Answer: B

Air movement removes the still, humid boundary layer around leaves, maintaining a steep water vapor concentration gradient that accelerates transpiration.

3. What is the spatial orientation of xylem and phloem inside a leaf vascular bundle?

  1. Xylem is located on the upper side; phloem is located on the lower side.
  2. Phloem is located on the upper side; xylem is located on the lower side.
  3. Xylem forms a central core entirely surrounded by phloem rings.
  4. Xylem and phloem are arranged in alternating concentric circles.
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Answer: A

In leaf vascular bundles (veins), xylem tissue faces toward the upper surface while phloem tissue faces toward the lower surface.

4. What primary physiological event initiates stomatal opening in guard cells during daylight?

  1. Passive loss of water to surrounding cells
  2. Active transport of potassium ions (K+) into guard cells
  3. Accumulation of abscisic acid (ABA) within the vacuole
  4. Efflux of sucrose out of guard cell cytoplasm
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Answer: B

In daylight, active transport pumps K+ ions into guard cells, lowering their solute potential and driving osmotic influx of water to increase turgidity.

5. What is the fluid matrix surrounding grana in a chloroplast called, and what reaction occurs there?

  1. Matrix; Light-dependent reaction
  2. Stroma; Light-independent reaction (Calvin cycle)
  3. Lumen; Photolysis of water
  4. Cytosol; Glycolysis
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Answer: B

The stroma is the fluid-filled interior of the chloroplast where dark reactions / Calvin cycle take place using soluble enzymes.

6. Which combination of factors causes guard cells to lose turgidity and become flaccid at night?

  1. Accumulation of K+ ions and osmotic entry of water
  2. Outflow of K+ ions, increasing water potential, and osmotic loss of water
  3. High rates of photolysis generating ATP inside guard cells
  4. Increased active pumping of protons into guard cell vacuoles
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Answer: B

At night, K+ ions leave guard cells, raising internal water potential and causing water to move out via osmosis, making guard cells flaccid.

7. What happens to a plant when environmental light intensity remains below its compensation point for an extended period?

  1. Glucose accumulation increases rapidly.
  2. Rate of photosynthesis exceeds cellular respiration.
  3. Stored organic reserves are depleted, leading to eventual plant death.
  4. Stomata remain permanently open to absorb excess oxygen.
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Answer: C

Below the compensation point, respiration breaks down organic molecules faster than photosynthesis produces them, depleting energy reserves.

8. Which phytohormone induces stomatal closure during severe soil water deficit or drought stress?

  1. Auxin
  2. Gibberellin
  3. Abscisic acid (ABA)
  4. Cytokinin
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Answer: C

Abscisic acid (ABA) signals guard cells to release potassium ions during water stress, causing water loss and stomatal closure to prevent dehydration.

9. Which environmental condition results in the LOWEST rate of transpiration?

  1. High light intensity, warm temperature, low humidity, strong wind
  2. Low light intensity, cold temperature, high air humidity, calm air
  3. High light intensity, hot temperature, dry air, moderate wind
  4. Moderate light intensity, warm temperature, low air humidity, breezy air
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Answer: B

Transpiration slows down in low light (stomata closed), low temperature (less kinetic energy), high humidity (narrow vapor gradient), and calm air.

10. Where do light-dependent reactions of photosynthesis specifically take place inside the chloroplast?

  1. Stroma matrix
  2. Thylakoid membrane
  3. Outer chloroplast membrane
  4. Intermembrane space
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Answer: B

Light-dependent reactions occur within thylakoid membranes, which contain chlorophyll pigments and electron transport chains.

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