Photoperiodism (Gr. Phos - Light)

Photoperiodism is physiological changes in animals and plants that are associated with the change of day and night.

Many plant and animal species exhibit seasonal changes in physiology and behavior that are synchronized with the cycle of day and night throughout the year. These cyclical changes are called photoperiodic reactions.

In plants, photoperiodism manifests itself in the change of phases of growth and development. For example, in many plant species, flowering and fruiting occur only during a certain length of daylight hours. Plants can be long-day plants, requiring long daylight hours to flower, or short-day plants, flowering under short daylight hours.

In animals, photoperiodism influences seasonal changes in physiology, behavior, and coloration. For example, in birds it triggers seasonal migrations, molting and reproduction. In mammals, photoperiodism affects hibernation, molting, reproduction, and other seasonal processes.

Thus, photoperiodism allows organisms to predict seasonal changes and adapt to them in advance for survival and reproduction. This is an important mechanism for the interaction of living organisms with their environment.