Class 11 NEET Biology Plant Growth and Development

(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, $\text{i.e., } P_{R}$ and $P_{FR}$ (i.e., red light and far red light absorbing forms) and these 2 forms are interconvertible. $P_{R} \xrightleftharpoons[\text{ Far red light }]{\text{ Red light }} P_{FR}$ It is involved in the perception of photoperiodic stimuli controlling flowering and other morphogenetic phenomenon in plants.