- This is controlled by plant genes. The way in which living organisms respond to changes in day length.
- An example of this is deciduous trees as they lose their leaves in winter as the days become shorter.
- The plants use the change in day length to help them grow or flower at the right time. Responses to changing day length are called photoperiodism.
- Plants can tell when it is spring from winter as the days get longer. As a result, their seeds sense this and germinate even if the plant has already died.
- Some plants grow throughout winter but grow faster in lengthening days as a response. In autumn, the days get shorter and the plants stop growing to prepare for winter.
- Plant species are often synchronised when releasing their pollen as it is an important stage for creating the next generation. For example, millions of crop plants harmonise their life cycles to produce grains at the same time.