Phytochrome is a plant pigment found in flowering plants that can detect the presence or absence of light and is involved in regulating many processes that are linked to day length (photoperiod) such as seed germination and initiation of flowering i.e. photoperiodism. It consists of a light detecting portion called a chromophore, linked to a small protein and exists in two interconvertible forms Pr and Pfr with two different physical properties, particularly in ability to bind to membranes. Pr absorbs red light while Pfr is physiologically active form.