Q38 / 200 · NEET 2007 · Botany

The wavelength of light absorbed by $\mathrm{P}_r$ form of phytochrome:

  • Correct answer
    A
    $680 \mathrm{~nm}$
  • B
    $720 \mathrm{~nm}$
  • C
    $620 \mathrm{~nm}$
  • D
    $640 \mathrm{~nm}$

Solution

Light acts as a signal to initiate and regulate photoperiodism and photomorphogenesis. There are two light-sensing systems involved in these responses, the blue light-sensitive system and the red light-sensitive or phytochrome system. The action spectrum of the light needed for \(\mathrm{P}_{\mathrm{r}}\) responses is at about 680 nm. So, the correct answer is '680 nm'

Hence, the correct answer is option: 'A'.

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