Question

Which of these is the physiologically active form of phytochrome?

• A. $P_{730}$
• B. $P_{660}$
• C. $P_{700}$
• D. $P_{680}$

Answer 1

Answer: (A)

$P_{730}$

Phytochrome pigment in plants exists in two interconvertible forms- Pr and Pfr. Pfr absorbs far-red light of 730 nm wavelength. The Pfr form is the active form that initiates biological responses. When Pfr absorbs far red light, it is converted to the Pr form. Pfr can also spontaneously revert to the Pr form in the dark over time