Photoperiod affects reproduction in seasonal breeders, both plants and animals.

Photoperiod, which refers to the duration of light and darkness in a 24-hour period, plays a significant role in regulating reproduction in many seasonal breeders, including both plants and animals. 
Some plants are categorized as short-day plants, meaning they require a shorter duration of light than darkness to initiate flowering. Others are long-day plants, which require a longer duration of light. There are also day-neutral plants that are not strongly influenced by photoperiod.
In the animal kingdom, many species are seasonal breeders, and photoperiod serves as a key environmental cue for regulating reproductive activities.