Edit page | Page history | Printable version

photoperiod

(Science: ecology) Recurring cycle of light and dark periods. The natural photoperiod is approximately 24 hours, and the ratio of light to dark hours slowly changes over the course of a year. In controlled experiments, the photoperiod is usually (but not necessarily) retained at 24 hours, and the light:dark ratio is typically constant. The amount of hours in a day where the environment is either light or dark.