Ibechillin
Masochist Educator
Loc dog This should help:
How flowering Is Initiated In Cannabis (and other short day plants):
The phytochromes are a family of chromoproteins with a linear tetrapyrrole chromophore, similar to the ringed tetrapyrrole light-absorbing head group of chlorophyll. Phytochromes have two photo-interconvertible forms: Pr and Pfr.
Pr absorbs red light (~660nm - ~729nm) and is immediately converted to Pfr.
Pfr absorbs far-red light (~730nm - ~800nm) and is quickly converted back to Pr.
Pfr naturally converts to Pr in darkness over time (after about 2 - 2.5 hours)
Absorption of red or far-red light causes a massive change to the shape of the chromophore, altering the conformation and activity of the phytochrome protein to which it is bound. Pfr is the physiologically active form of the protein; therefore, exposure to red light yields physiological activity. Exposure to far-red light inhibits phytochrome activity. Together, the two forms represent the phytochrome system.
Unfiltered sunlight is rich in red light but deficient in far-red light. Therefore, at sunrise, all the phytochrome molecules in a leaf quickly convert to the active Pfr form, and remain in that form until sunset. In the dark, the Pfr form takes 2 - 2.5 hours to slowly revert back to the Pr form. By sensing the Pr/Pfr ratio at sunrise, a plant can determine the length of the day/night cycle. In addition, leaves retain that information for several days, allowing a comparison between the length of the previous night and the preceding several nights. If the night is long (as in winter), all of the Pfr form reverts. If the night is short (as in summer), a considerable amount of Pfr may remain at sunrise.
Link to source:
https://courses.lumenlearning.com/ivytech-bio1-1/chapter/plant-responses-to-light/
So to clear up any confusion:
Its the ratio of how much time either Pr or Pfr is the active phytochrome that dictates the flowering response in short day plants like cannabis.
Red light between 660nm - 729nm converts Pr in the plant to Pfr which helps the plant remain in veg.
Infra red light between 730nm - 800nm converts Pfr in the plant to Pr which helps the plant begin flowering.
Naturally at sundown/lights out it takes around 2 - 2.5 hours of uninterrupted darkness before PFR begins converting to PR. Then the plant needs 10 more hours uninterrupted darkness to shift towards flowering expression totaling 12 hours dark. My research suggests blasting plants with 730nm far red for ~30 minutes after sundown/lights off will force plants to flower with only 10 hours darkness since your not having to wait the extra 2 hours for PFR to convert to PR naturally. This could be used to make outdoor and greenhouse plants begin and finish flowering earlier in the season as well.
How flowering Is Initiated In Cannabis (and other short day plants):
The phytochromes are a family of chromoproteins with a linear tetrapyrrole chromophore, similar to the ringed tetrapyrrole light-absorbing head group of chlorophyll. Phytochromes have two photo-interconvertible forms: Pr and Pfr.
Pr absorbs red light (~660nm - ~729nm) and is immediately converted to Pfr.
Pfr absorbs far-red light (~730nm - ~800nm) and is quickly converted back to Pr.
Pfr naturally converts to Pr in darkness over time (after about 2 - 2.5 hours)
Absorption of red or far-red light causes a massive change to the shape of the chromophore, altering the conformation and activity of the phytochrome protein to which it is bound. Pfr is the physiologically active form of the protein; therefore, exposure to red light yields physiological activity. Exposure to far-red light inhibits phytochrome activity. Together, the two forms represent the phytochrome system.
Unfiltered sunlight is rich in red light but deficient in far-red light. Therefore, at sunrise, all the phytochrome molecules in a leaf quickly convert to the active Pfr form, and remain in that form until sunset. In the dark, the Pfr form takes 2 - 2.5 hours to slowly revert back to the Pr form. By sensing the Pr/Pfr ratio at sunrise, a plant can determine the length of the day/night cycle. In addition, leaves retain that information for several days, allowing a comparison between the length of the previous night and the preceding several nights. If the night is long (as in winter), all of the Pfr form reverts. If the night is short (as in summer), a considerable amount of Pfr may remain at sunrise.
Link to source:
https://courses.lumenlearning.com/ivytech-bio1-1/chapter/plant-responses-to-light/
So to clear up any confusion:
Its the ratio of how much time either Pr or Pfr is the active phytochrome that dictates the flowering response in short day plants like cannabis.
Red light between 660nm - 729nm converts Pr in the plant to Pfr which helps the plant remain in veg.
Infra red light between 730nm - 800nm converts Pfr in the plant to Pr which helps the plant begin flowering.
Naturally at sundown/lights out it takes around 2 - 2.5 hours of uninterrupted darkness before PFR begins converting to PR. Then the plant needs 10 more hours uninterrupted darkness to shift towards flowering expression totaling 12 hours dark. My research suggests blasting plants with 730nm far red for ~30 minutes after sundown/lights off will force plants to flower with only 10 hours darkness since your not having to wait the extra 2 hours for PFR to convert to PR naturally. This could be used to make outdoor and greenhouse plants begin and finish flowering earlier in the season as well.
