24 Hours Of Dark before switch to flower

[f-e]

Posted this a few days ago, hope it helps. Ive never done the 24hr dark personally, as others have said seems like it will shock them. I havent tryed it but blasting plants with Far red lighting during the dark period supposedly helps keep them in veg.



Only the branch(es) exposed to light will reveg during flowering (response to hormone buildup). Im pretty sure i saw a quote by Sam_Skunkman that said a plant can be in veg and flowering at the same time by only covering some of the branches to flower. My guess is a light leak somewhere near the top of the plant. Hermie all over the plant is more of a genetic or damaging stress it seems.

Info on flowering cannabis:

Cannabis plants are described as long evening or brief day plants because they need a long period of darkness to cause the plant’s hormones to change from vegetative growth to flowering. These light receptors are color pigments in the leaves called Phytochrome Red (PR) and Phytochrome Far Red (PFR). These pigments acquire their labels from the types of light they take in. These two pigments chemically react to the light and trigger the plant to flower or not:

PR absorbs red light in between 660 and 760 nm.

PFR takes in red light between 760 and 800 nm.

In cannabis plants, the typical presence of PFR turns off the flowering signal. PFR is quickly created when plants are left open to light which contains far-red wavelengths like MH, HPS and CMH. The degree of PFR can be manipulated by adjusting the photoperiod. When there is light, the PFR and PR keep a balance. When the sunlight decreases, or the lighting schedule changes, the darkness slowly switches PFR to PR. As a result of this, PR levels gradually enhance and the PFR gradually lessen throughout the dark duration. This reduced level of PFR indicates to the plants that autumn is approaching, and the marijuana begins flowering.

Basically, the existence of PFR, due to long hours of light and short hours of darkness, keeps the plants in the vegetative phase. By allowing plants to sit in 24hrs of darkness before flowering it allows the PR hormone to buildup and jump start flowering quicker.

Link To Source:

https://www.greencultured.co/flowering-marijuana-light-cycles/

Hello.

So PFR, created by far red shorter than 760nm, inhibits flowering. Okay..

A lack of it doesn't start flowering though. Not as a lone trigger anyway. As seen in led grows using burple .

Most people trying led are 'wishful finking' so an earlier start would almost certainly of been picked up on. Or has it?

I wonder if they could stray from 12/12.

Back on topic, if led gardeners are not noticing the lower pfr helping them, then I don't imagine us extending the sleep would help by using that mechanism.

 

[OakyJoe]

subbed

 

[Ibechillin]

Edited, see post #31.

PFR 760nm to 800nm activates the shade avoidance response in plants and causes stretchy growth and further node spacing.

The ratio between red and blue light in the 400nm-700nm range effects growth as well.

As someone with a biological science background and 35+ years growing experience I think I can add further to the discussion.

The lower the colour of your light the better the calyx to leaf ratio. Temperature is also a factor, with colder temperatures typically resulting in leafier buds, especially in sativa's and hybrids.

Jack Herer clone from the early 2000's, here is the same Jack Herer clone grown under CMH and HPS. Under HPS, the branches stretched considerably more and filled in with solid, almost leafless buds. The 3000K CMH (plus cooler temps) shortened the internodes dramatically and result in much leafier buds.

The same clone, same grow box, same watts (600hps v 2 x 315w cmh), same nutrient, same media, same grower lol

I prefer HPS because of this one significant difference. Abundant red light gives good stretch and stacks flowers.

Both Jack clones were the same as always - advanced clones about 8-10 inches in height raised under florescent light. Veg was done under the flowering light in both cases.

2100K 600w Sunmaster single-ended hps bulb: Veg takes about 2 - 2.5 weeks, Stretch during the first 4 weeks of flowering is around 150 - 200%. At maturity (around 7 weeks) the top 18 inches of all branches are laden with solid, leafless buds as shown in the photo at around 6.5 weeks.

3100K CMH: Veg takes about 2.5 - 3.5 weeks as they take longer to get to sufficient size. Stretch during the first 4 weeks of flowering is about 100%. The photo was taken at 4.5 weeks after the stretch was done. At maturity the only the top 6 to 10 inches have solid buds and those below the first 4-5 inches are more leafy and not as dense.

I have found from my experience with many bulb types that the ideal spectral ratio in a flowering lamp is about 2:1 red:blue ratio. This contains enough blue light to keep internode distances short, but not so much that it causes the more leafy growth seen in sunlight or cool MH bulbs. 3000K COB LEDs typically satisfy this spectral balance quite well, and many contain even significant output in the 730nm FR spectrum, which seems to result in faster budset and a more vigorous flower development; though I need to test this in a more controlled setting.

In my experience over 15 years, the BEST inddor results I have seen (in terms of overall quality) are from 3000K COB LEDs with 90CRI spectrum. The second best from warm-white metal halide/CMH. Third best from the hybrid MH/HPS combo bulbs. Fourth best HPS (good yield but quality just OK). Blue MH has not been great for flowering since it grows more leaf than buds.

 

[f-e]

.

You got it backwards, PFR created by far red wavelengths longer than 760nm to 800nm are supposed to inhibit flowering. Below 760nm to 660nm are shorter wavelengths that produce PR which are supposed to encourage flowering. 662nm is the chlorophyl A absorption peak as well.

PFR 760nm to 800nm activates the shade avoidance response in plants and causes stretchy growth and further node spacing.

The ratio between red and blue light in the 400nm-700nm range effects growth as well.

Oh yes, longer not shorter. I even gave it a second look myself, knowing it wasn't right. Since 40 I have been making silly mistakes. Since my mid 40s, daily. Now pushing towards 50, I can see myself in a mental institution before long.

So it seems the plant is watching the two, and when the longer more penetrative light is arriving with greater ease, it knows to forget making buds and to shift it's arse into gear.

Shit man. Christmas and new year have ruined me. I don't remember where I was heading. I can just about relate water coffee and sugar. I have been sat looking at a green light for about 5 hours, to do further experimentation growing without either, or anything really. I just can't get my shit together though.

I give up lol

 

[shaggyballs]

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[hunter77]

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You got it backwards, PFR created by far red wavelengths longer than 760nm to 800nm are supposed to inhibit flowering. Below 760nm to 660nm are shorter wavelengths that produce PR which are supposed to encourage flowering. 662nm is the chlorophyl A absorption peak as well.

PFR 760nm to 800nm activates the shade avoidance response in plants and causes stretchy growth and further node spacing.

The ratio between red and blue light in the 400nm-700nm range effects growth as well.

Ibechillin are they your plants ?

 

[Ibechillin]

Those are Natural High's Plants and pics not mine haha.

This article from canna explains it well:

http://www.cannagardening.com/effect-of-red-and-far-red-light-on-flowering

 

[hyposomniac]

.

You got it backwards, PFR created by far red wavelengths longer than 760nm to 800nm are supposed to inhibit flowering. Below 760nm to 660nm are shorter wavelengths that produce PR which are supposed to encourage flowering. 662nm is the chlorophyl A absorption peak as well.

PFR 760nm to 800nm activates the shade avoidance response in plants and causes stretchy growth and further node spacing.

The ratio between red and blue light in the 400nm-700nm range effects growth as well.

I haven't been able to find a lot of credible info about altering calyx to leaf ratio, but I find this to match my experiences.. And why I'm ditching the cmh.

 

[f-e]

Metal halides and before them mercury, have always been associated with veg growth. Stronger blue means mid summer. No shade. No rush to bloom. Keep making solar panels.

Edit: Perhaps I should explain, that longer wavelengths have better penetration. As we move towards the blue end, where they get shorter, it's easier to block them. In winter, blue light is diminished much more than red, because as we move from the sun, and the distance the light travels increases, the blue is eroded more. Pot is seen primarily as photoperiod sensitive, but plants in general fall in other grounds such as being sensitive to the colour of the light. Pot shows it also pays an interest. Though we seem to ignore this on the whole.
We suffer from sad in winter, and the answer is lights that make the home look like an igloo. More winter like some would say. But it's putting the blue back. We are sensitive to it, just like the plants. But it's rarely spoke of.

Light BETWEEN 760 and 800nm is stopping flower for a different reason. It's not causing short internodes and big leaves. It's moving it's energy from veg or flower, to competing. The males must get height to spread over the biggest area, and the girls must get up there to catch some and make the strongest seeds. Each plant is in it to win. It's no surprise that lots of 760+ caused a male for somebody. With the light so heavily tipped away from mid summer, it probably thought snow was about to fall.


I surmise the cmh is a great veg light, and turning it off 12 hours a day will initiate flowering. However, it's still telling something that their is lots of time left. So it's not totally committed to flowering. Even after 6 weeks. It's just that bit greener and more leafy. While making a difference to resin production. Perhaps directly linked to the time of year it's thinking about. Only the better yields reported by many, make me still look at them as flowering lights.


I dunno, but you can see it happening. That's all that truly matters to me.

 

[Brother Nature]

Anyway my question was Will this cause a build up of floragen?

It looks like tha answer to this question is yes, but also dependent on many other factors.


Florigen and anti-florigen: flowering regulation in horticultural crops - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5903977/

 

[Ibechillin]

I found a better explanation of phytochrome red/far red and wanted to share to help explain it better and clear up any confusion:

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 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, have not tried it myself.