Phototropism, plant growth towards or away from light, and photoperiodism, regulation of flowering, and other developmental transitions by day/night length.
In phototropism, a plant bends or grows directionally in response to light. Shoots usually move towards the light; roots usually move away from it.
In photoperiodism flowering and other developmental processes are regulated in response to the photoperiod, or day length.
In many plants, photoperiodism is controlled by the overlap between the day length cue and the plant's internal circadian rhythms.