Question

Phytochrome is

• A. Absorption of blue light by leaves.
• B. Absorption of PR and PFR in reversible manner.
• C. Absorption of red light with wavelength 660m$\mu$.
• D. Absorption of far-red light with wavelength 740m$\mu$.

Answer 1

The correct option is B Absorption of PR and PFR in reversible manner.

Phytochrome is the absorption of PR and PFR in reversible manner. The phytochrome exist in two different forms - Pr and Pfr
The Pr form:

1. Absorbs at a peak of 666nm. It is the form synthesized in dark - grown seedlings.
2. When Pr absorbs red light, it is converted to the Pfr form.

The Pfr form:

1. Absorbs at a peak of 730 nm.
   
2. The Pfr form is the active form that initiates biological responses.
   
3. When Pfr absorbs far red light, it is converted to Pr form.