The alternation of light and dark periods that affects the physiological activities of many plants. As the day length changes through the year, various responses are shown by plants, depending on whether they are * long-day or * short-day species. An example is the onset of flowering, triggered in a particular plant by a specific photoperiod. The length of the light period is more important than the intensity of the light. It has also been shown that the effect of a long dark period can be nullified by a brief period of light. See also phytochrome. |
