Photoperiodism

Definition

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.

5 Must Know Facts For Your Next Test

1. Photoperiodism is controlled by the plant's perception of light through photoreceptors like phytochromes and cryptochromes.
2. Plants are classified based on their photoperiodic response into short-day plants, long-day plants, and day-neutral plants.
3. The critical night length is a key factor that triggers flowering in short-day and long-day plants.
4. Phytochrome exists in two forms (Pr and Pfr) which convert based on red and far-red light exposure, helping measure day length.
5. Photoperiodism also affects other growth responses such as leaf abscission and tuber formation.

Review Questions

• What role do phytochromes play in photoperiodism?
• How are short-day plants different from long-day plants regarding their flowering response?
• What is the significance of critical night length in photoperiodism?

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.