Phytochromes are dimeric proteins with critical roles in perceiving day length and the environmental signals that trigger flowering. Night break (NB) and the red to far-red light ratio (R:FR) have been used extensively as tools to study the photoperiodic control of flowering. | Phytochrome B1-dependent control of SP5G transcription is the basis of the night break and red to far-red light ratio effects in tomato flowering