[Campbell Biology P.893] The aurea mutant of tomato has reduced levels of phytochrome and gr... | Practice Question

The aurea mutant of tomato has reduced levels of phytochrome and greens less than wild-type tomatoes when exposed to light. If researchers inject phytochrome from other plants into aurea leaf cells and expose them to light, a normal de-etiolation response occurs. What does this observation primarily indicate?

  • A: Phytochrome is the only factor required for de-etiolation.
  • B: The _aurea_ mutant has a defect in light perception, which can be overcome by external phytochrome.
  • C: De-etiolation is an irreversible process once initiated.
  • D: Carotenoids are responsible for the greening response in wild-type tomatoes.

Explanation

The description of the aurea mutant and the rescue experiment directly supports that phytochrome is essential for proper light perception leading to de-etiolation. The mutant lacks sufficient phytochrome, leading to impaired greening, which can be corrected by providing external phytochrome, thus restoring its ability to perceive light signals effectively.