Phototropism is growth toward light. Which choice states this correctly?

• A. Growth toward gravity
• B. Growth toward water
• C. Growth toward darkness
• D. Growth toward light

Answer: (D)

Phototropism is the growth of a plant toward light. This response happens when light direction is sensed by blue-light receptors, which trigger a redistribution of the growth hormone auxin to the shaded side of the stem. The auxin on that side causes cells to elongate more, bending the stem toward the light. That’s why growth toward light is the correct statement. The other directions describe different tropisms: growth toward gravity is gravitropism, toward water is hydrotropism, and growth toward darkness isn’t phototropism (plants may exhibit other light-related responses, but phototropism specifically means toward light).