In the process of systematic development, plants respond to the change of sunshine length, and the apical meristem differentiates from vegetative growth to reproductive growth, which is called photoperiod phenomenon. Besides constant temperature induction, the differentiation and formation of floral organs in plants must undergo a certain photoperiodic induction.
Ecological significance
In temperate zone, the temperature varies greatly in seasons, and the winter is prolonged with the increase of latitude. If plants can't form seeds before low temperature and frost come, they can't reproduce. In the process of long-term adaptation, many plants have formed the ability to perceive seasons through the length of day and night that is less affected by climatic conditions.
For example, some plants originating from high latitudes often blossom and bear fruit under the condition that the sunshine changes from short to long after spring warming, and flowering requires long sunshine. Some plants originated in low latitudes have the characteristics of short-day plants, and bloom in autumn with shorter and shorter days, which is beneficial to make full use of the long warm period in low latitudes.