Question : Describe the concept of Phytochrome.

1.	Question : Describe the concept of Phytochrome.
Answer» Solution :PHYTOCHROME is a bluish biliprotein pigment responsible for the perception of light in photo physiological process. Butler et al., (1959) named this pigment and it exists in two interconvertible forms: (i) red light absorbing pigment which is designated as `P_r`and (ii) far red light absorbing pigment which is designated as `P_(fr)` The `P_r`form absorbs red light in 660 nm and changes to` P_r`. The `P_r`form absorbs far red light in 730 nm and changes to `P_r` . The` P_r`form is biologically inactive and it is stable whereas `P_(fr)`form is biologically active and it is very unstable. In short day plants, `P_r`promotes flowering and Pr inhibits the flowering whereas in long day plants flowering is promoted by `P_(fr)`and INHIBITED by` P_r`form. `P_(fr)`is always associated with hydrophobic area of membrane systems while `P_r`is found in diffused STATE in the cytoplasm. The interconversion of the two forms of phytochrome is mainly involved in flower induction and also additionally plays a role in seed germination and changes in membrane CONFORMATION.

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