Plants use day length as a cue to prepare for winter.

We have seen how plants use day length to control when flowers are produced. Day length also triggers other developmental events, particularly ones that allow plants that persist for more than a year to prepare for winter. One such developmental change is the formation of storage organs, for example in roots. Carbohydrates that accumulate in these structures can support the growth of new leaves and stems the following spring.

A second developmental change in response to day length is the formation of overwintering buds. As the days begin to shorten, plants stop producing photosynthetic leaves and begin forming bud scales. Bud scales surround and protect the meristem from ice and water loss. The formation of bud scales accompanies a series of metabolic changes that allow meristems to remain in a dormant state throughout the winter. For example, plugs are produced that block the plasmodesmata between the meristem and the rest of the plant. These plugs prevent any growth-stimulating compounds from reaching the meristem.