Plant shoots exhibit phototropism towards light

Steps:

• Identify the experimental setup: a young plant shoot exposed to unilateral light from one side.
• Recall that phototropism causes shoots to grow towards light due to auxin hormone redistribution.
• Predict growth direction: the shoot bends towards the light source over time.
• After 4 hours, the shoot curves noticeably in that direction.

Why A is correct:

• Option A depicts the shoot bending towards the light, aligning with the definition of positive phototropism where auxin accumulates on the shaded side, promoting cell elongation there.

Why the others are wrong:

• B shows straight growth, ignoring phototropic response to unilateral light.
• C illustrates bending away from light, which contradicts positive phototropism.
• D indicates no growth or wilting, unrelated to directional light stimulus.

Final answer: A