[Campbell Biology P.943] A plant seedling is placed in a dark room with a single light sourc... | Practice Question

A plant seedling is placed in a dark room with a single light source to its left. Over several days, the seedling bends towards the light. According to the "Environmental Response" section, which of the following best describes the underlying biological process responsible for this phenomenon?

  • A: The plant is directly consuming light energy for growth, causing it to lean towards the source.
  • B: Specialized photoreceptors detect the light, activating signal transduction pathways that lead to cellular responses in growth direction.
  • C: Hormones transported throughout the plant's body cause rapid cell division on the illuminated side, bending the stem.
  • D: The plant's roots are seeking water from the light source, pulling the stem in that direction.

Explanation

The "Environmental Response" section states: "Specialized organs sense environmental signals... Environmental signals activate specific receptor proteins, triggering signal transduction pathways that initiate cellular responses coordinated by chemical and electrical communication." The example given for light detection mentions photoreceptors in a sunflower and insect eyes.