1. the period of the day during which an organism is exposed to light, especially in a 24-hour cycle.
Usage: biology; ecology

Examples

• The photophase of a 24-hour day cycle typically lasts about 12 hours in temperate regions.
• Many plants adjust their growth patterns based on the length of the photophase.
• Insects often become more active during the photophase when light is available.
• The photophase influences the circadian rhythms of most living organisms.
• Researchers manipulated the photophase in the laboratory to study its effects on animal behavior.