(d) : Phytochrome is a bright blue or bluish green pigment which was first of all isolated from plasma membrane of alga Mougeotias. It is a photoreceptive pigment. Phytochrome has a light absorbing or light detecting portion (the chromophore) attached to small protein of about 1,24,000 daltons. Phytochrome occurs in 2 forms, i.e.,PR and PFR (i.e., red light and far red light absorbing forms) and these 2 forms are interconvertible.
PR
‌‌ Red light ‌
⇌
‌ Far red light ‌
PFR
It is involved in the perception of photoperiodic stimuli controlling flowering and other morphogenetic phenomenon in plants.