Photoperiodism: Flowering in certain plants depends on a combination of light and dark exposures and also on the relative duration of light and dark periods. This response of plants is called photoperiodism.
Flowering is an important step towards seed formation. Hence, phtoperiodism plays an important role in plant evolution.
Vernalisation: In some plants, flowering is quantitatively or qualitatively dependent on exposure to low temperature. This phenomenon is called vernalisation. Flowering is promoted during the period of low temperature because of vernalisation.
