Phytochrome : (a) It is the pigment which is responsible for flowering.
(b) It makes the plant sensitive to light effect.
(c) It is known as light absorbing pigment and is responsible for photosensitiveness of plants.
(d) It participates in flowering. In long day plants, the light interruption of dark period does not prevent flowering.
(e) If the light is by infra-red, the flowering gets promoted.
(f) Phytochrome occurs in two forms-one red absorbing (PR) and the other far red absorbing (PFR).
(g) Both the forms are photo-chemically interconvertible.
(h) The red absorbing form after absorbing the red light is converted into far red form.
(i) They absorbs the infra-red light and is converted back into red absorbing form of pigment.
(j) Flowering is considered a phytochrome mediated process.
(k) Photoperiodism controls flowering in plants. Short- day plants like Xanthium, Chrysanthemum require a relatively short day high period and a continuous dark period of about 14-16 hours for flowering.
(l) Dark period is more important to induce flowering
than the light period. Flowering can be induced in short day plants by red light treatment followed by far red light treatment.