Summary
Responses such as flowering triggered by the length of day and night, mediated by phytochrome.
In depth
Short-day plants (chrysanthemum) flower when nights are long; long-day plants (spinach) flower with short nights. Plants actually measure night length. Phytochrome Pr and Pfr forms interconvert with red and far-red light.
Critical night length matters, and a brief flash of light in the dark period can prevent short-day plants flowering. The signal florigen (FT protein) is produced in leaves and travels to the shoot apex.
Key idea: plants measure the length of darkness, not light.
Frequently asked questions
What is Photoperiodism?
Responses such as flowering triggered by the length of day and night, mediated by phytochrome.
Which area of biology covers Photoperiodism, and how advanced is it?
Photoperiodism is one of the 56 topics in Plant Biology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Phytochrome Signalling, Plant Hormones, Stomata.
Can you give an example of Photoperiodism?
Growers control flowering with blackout curtains.
What should I learn before Photoperiodism?
Work through the Beginner topics in Plant Biology first, such as Plant Kingdom, Photosynthesis, Chlorophyll, then return to Photoperiodism. Intermediate topics assume the Beginner vocabulary.
What topics are related to Photoperiodism?
The closest topics to Photoperiodism are Phytochrome Signalling, Plant Hormones, Stomata, Vernalisation. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Photoperiodism?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Photoperiodism. To practise the whole of Plant Biology, use the Plant Biology quiz.
How is Photoperiodism different from Phytochrome Signalling?
Photoperiodism: Responses such as flowering triggered by the length of day and night, mediated by phytochrome. Phytochrome Signalling: Red/far-red photoreceptors toggle between forms to control germination, shade avoidance and flowering. Read both side by side and note what each one explains.
How should I study Photoperiodism step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Phytochrome Signalling and explain the difference aloud. Finally, take the Plant Biology quiz and come back to this page for any question you miss.