1. Phototropism is the growth response of a plant part to:
A.
Light
B.
Gravity
C.
Water
D.
Touch
Correct Answer:
Light
Explanation:
Phototropism is the directional growth response of a plant part to light.
2. The shoot of a plant generally shows which type of phototropism?
A.
Positive phototropism
B.
Negative phototropism
C.
No phototropism
D.
Random phototropism
Correct Answer:
Positive phototropism
Explanation:
Plant shoots usually bend and grow toward the source of light, showing positive phototropism.
3. When light falls on a shoot from one side, auxin mainly moves toward the:
A.
Shaded side
B.
Lighted side
C.
Root tip only
D.
Upper surface only
Correct Answer:
Shaded side
Explanation:
Unilateral light causes auxin to redistribute toward the shaded side of the shoot.
4. In a shoot exposed to light from one side, cells on the shaded side grow:
A.
More rapidly
B.
More slowly
C.
At exactly the same rate
D.
Only after flowering
Correct Answer:
More rapidly
Explanation:
Auxin promotes greater cell elongation on the shaded side of the shoot, causing it to bend toward the light.
5. The bending of a shoot toward light occurs mainly because of unequal:
A.
Cell elongation on its two sides
B.
Seed production on its two sides
C.
Water absorption by its leaves
D.
Root branching on its two sides
Correct Answer:
Cell elongation on its two sides
Explanation:
Different rates of cell elongation on the illuminated and shaded sides make the shoot curve toward the light.
6. Which part of a young shoot primarily detects the direction of light during phototropism?
A.
Shoot tip
B.
Root cap
C.
Mature root
D.
Flower stalk base
Correct Answer:
Shoot tip
Explanation:
The tip of a young shoot perceives the direction of light and helps control the phototropic response.
7. If the tip of a young shoot is covered with an opaque cap, phototropic bending is generally:
A.
Prevented
B.
Increased immediately
C.
Changed into root growth
D.
Unaffected in every case
Correct Answer:
Prevented
Explanation:
An opaque cap blocks light from reaching the shoot tip, preventing the normal perception needed for phototropic bending.
8. A shoot receiving light equally from all directions usually grows:
A.
Straight upward
B.
Strongly toward the left
C.
Strongly toward the right
D.
Only downward
Correct Answer:
Straight upward
Explanation:
Equal light from all directions does not create unequal auxin distribution, so the shoot usually grows straight.
9. Which hormone is mainly associated with the bending of shoots during phototropism?
A.
Auxin
B.
Ethylene
C.
Abscisic acid
D.
Cytokinin
Correct Answer:
Auxin
Explanation:
Auxin redistributes in response to one-sided light and promotes differential elongation that bends the shoot.
10. The bending of a shoot toward one-sided light helps the plant to:
A.
Receive more light
B.
Avoid all water loss
C.
Stop producing auxin
D.
Prevent root growth
Correct Answer:
Receive more light
Explanation:
Positive phototropism directs the shoot toward light, helping the plant receive more light for photosynthesis.
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