Photoperiodism is the physiological reaction of organisms to the length of day or night. In plants, it influences processes such as flowering, seed germination, and dormancy.
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Photoperiodism is controlled by the plant's perception of light through photoreceptors like phytochromes and cryptochromes.
Plants are classified based on their photoperiodic response into short-day plants, long-day plants, and day-neutral plants.
The critical night length is a key factor that triggers flowering in short-day and long-day plants.
Phytochrome exists in two forms (Pr and Pfr) which convert based on red and far-red light exposure, helping measure day length.
Photoperiodism also affects other growth responses such as leaf abscission and tuber formation.
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Related terms
Phytochrome: A photoreceptor protein in plants that detects light and helps regulate photoperiodism.
Short-Day Plant: A plant that flowers when the nights are longer than its critical night length.
Long-Day Plant: A plant that flowers when the nights are shorter than its critical night length.