Photoperiodism
Photoperiodism is the ratio of light and dark periods and the response of plants to this.
Additional Information
This phenomenon affects flowering and plant dormancy. Plants can be classified as long day, short day or day neutral. The length of the dark period is actually more important than the length of the light period. The pointsettia is a well known example of a greenhouse plant that blooms in response to exposure to a dark period over a certain length of time.
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