Phytochrome system is also known as red light sensitive system. Phytochrome are pale blue pigments which proteinaceous and present in higher plants. Its main function is absorption of light and exists in two stable forms, Pred or Pr, and Pfr or Pfar red. Pr is the red light absorbing form and Pfr is the far red light absorbing form. Either of the forms absorbs light and get converted to other forms. Phytochrome regulates the germination of seed and it also initiates elongation of seedlings, induction of flowering etc.