Which statement best illustrates phototropism (a plant tropism)?

• A. A plant closes its leaves rapidly when touched.
• B. A cactus opens its stomata primarily at night to reduce water loss.
• C. A seedling grows toward a light source placed on one side of the plant.
• D. A plant produces flowers only after experiencing long nights.

Answer: (C)

Verified step by step guidance

1. Understand that phototropism is a plant's growth response to light, where the plant grows towards or away from a light source.
2. Review each statement and identify whether it describes growth or movement in response to light specifically.
3. The first statement describes a rapid leaf closure when touched, which is a response to touch (thigmotropism), not light.
4. The second statement involves stomata opening at night to reduce water loss, which is related to water conservation and not growth towards light.
5. The third statement describes a seedling growing toward a light source, which directly illustrates phototropism as it involves directional growth in response to light.