[Campbell Biology P.905] Based on Figure 39.15 and its accompanying text, which wavelength r... | Practice Question

Based on Figure 39.15 and its accompanying text, which wavelength range of light is most effective in inducing phototropic curvature in maize coleoptiles?

  • A: Around 660 nm (red light)
  • B: Around 730 nm (far-red light)
  • C: Wavelengths below 500 nm, particularly blue light around 436 nm.
  • D: Wavelengths between 500 nm and 700 nm, primarily green and yellow light.

Explanation

Figure 39.15 a clearly shows a peak of phototropic effectiveness around 436 nm, with significant effectiveness for wavelengths below 500 nm. The caption explicitly states, 'This action spectrum illustrates that only light wavelengths below 500 nm blue and violet light induce curvature.'