Pr and Pfr LED supplementation

[Naindejardin]

Does anyone have experience adding additional 1.) Far Red ~730nm and 2.) more Red like 680nm? I currently run an 270W QB 3500k white with a few 680 epistars. Wondering if adding Far Red the last 15 minutes of light on and 15 with lights off would speed flower time by making plant “sleep”. And then with the addition of 30 minutes of Red in the AM to account for the PrFr ratio and not cause shade avoidance stretch (Emerson Effect)? Also, I would like to add a 395nm UV bar to come on at “noon” to increase potency. So, if anyone had tips or experience hacking the phytochrome let me know. I want to grow pure sativas at 12/12 in flower but also cut down time if anyone wants to critique my rationale.

 

[f-e]

395nm? That's disco lighting. It's a long way from the UV that causes a protection response. Which we can't do with LED's.

If you want to gain something from putting them to sleep faster, you should probably wake them up sooner. No 24h days.
If you put them to sleep sooner, but still give them 12 hours, nothing is likely to happen. Well.. you will see less stretch and lightening of the tops in early bloom I guess. As they won't try and stay awake after lights out.

UVB comes from reptile lamps. CFL's

 

[Naindejardin]

f-e well the light I was looking for UV was Fluence-Osram https://fluence.science/support-article/do-fluence-systems-emit-uv/, which as it seems the lambda max is actually 400nm so far end of UVA, almost violet/blue. Back to putting to bed and waking them up sooner, what would you do solely using LED? I’m not going to do a 10/14 because yield suffers.

 

[Naindejardin]

f-e however I believe you’re right about using the reptile UVB bulb, as UVB activates the UVR8 pathway in stress response in cannabis.

 

[Naindejardin]

https://m.youtube.com/watch?v=_QHEF7wCuFA This was one of the original videos that peaked my interest is anyone cares

 

[f-e]

10/14 is bad, because you don't need 14 hours sleep. Even if you can hit your DLI in 10 hours, the 14 is counterproductive. I have often thought about 10/10 as it might give 8.5 days in a week. It's an idea that comes up sometimes, but I have not seen it tried. That would be about 20% more bud per week. So I guess it's been tried but failed. I just didn't see it..

Emerson effect looks interesting. At first glance it's a great gain, yet somehow it boils down to nothing when implemented. I don't recall why. It just made more sense to add more normal red.

As you have 3500k+660s your red spectrum is quite full. As you turn up your lights, it will saturate first. This is a lighting limitation. You may never reach that limit, but adding more 660 would just lower the amount of power you could run before maxxing out that part of the spectrum. Causing plant stress. The 3500k has enough blue, but at the time the red becomes overwhelming, you could still add more blue. Plants expect the sun, so any area of the spectrum depressed in your LED's output, is an area you can add more power. Blue light seems associated with a wider range of smell and flavour. That's what I can tell, stood in a room full. Testing shows effects not so obvious.

 

[chilliwilli]

I'm not sure about the 730nm. There are older threads here(search 730nm or far red) and people have used it but more to increase the time the plants are lighted. Some guys used up to 14/10 and for the plants it should be more like 14/12. and u would get a bigger yield in same time.
Imo the problem is to get good timer to synchronize the lights. Maybe wifi socket can do that.

I'm also thinking about getting some 730nm leds to play with. I like sativas and hope to avoid to turn the lights down to 10/14 to speed up ripening and avoid reflowering.

 

[Naindejardin]

f-e I appreciate the input, gotta run an equilibria between yield and stress I guess. Or just a 315 CMH, I’d be full spectrum and add UV, too bad heat is the limit for me hence the LED infatuation.

 

[Naindejardin]

chilliwilli yeah the 730nm sounds interesting, but I feel all the research has been in the lab and hasn’t been practiced. I’d like to see a few more studies that are not geraniums, lettuce or wave petunias and see if indeed it works for short day plants. For sure don’t want reflowering or foxtails, I’m running a Thai/Malawi next, I want to get my lighting dialed in. However, if I can get pure sativas to flower on 12/12, win-win. A smart plug sounds great! Good idea.

 

[alpo]

f-e I appreciate the input, gotta run an equilibria between yield and stress I guess. Or just a 315 CMH, I’d be full spectrum and add UV, too bad heat is the limit for me hence the LED infatuation.

Do you think 315cmh is better than LEDs? (I have been asking this a lot on this site.)

 

[Naindejardin]

alpo from what I’ve seen at my friends (same soil, clones, etc) their plants look amazing. The end product is super sugary, pungent, etc. The kicker is that cooling costs are crazy, although still less than conventional MH or HPS. CMH definitely looks like sunlight. I don’t have the headspace either to run the 630w systems, LEDs are king for electric savings but I still think their spectrum needs work. All that being said I have 3500k white with 680 reds in there. Literally should be , instead meh. It matches the McCree PAR curve that’s why I think it’s antiquated. IMO, but take my opinion as a grain of salt ya know.

 

[alpo]

I think you can get a better spectrum than the sun for growing cannabis plants, just like you can make indoor environment better than the outdoor. sorry to go offtopic

 

[chilliwilli]

Very good post

Posted this recently:

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/iv...nses-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 2 - 2.5 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.

 

[chilliwilli]

[No message]

 

[chilliwilli]

[No message]

 

[chilliwilli]

If u hit google with "far red icmag" more threads show up. There is already a lot of practical experience with 730nm sleep inducing on icmag.

 

[alpo]

all the LED grow lights im looking at use 660nm, which doesn't really help when I prefer flowers over veg.

 

[Naindejardin]

chilliwilli Wow thanks for the digging. That’s what I was looking for!

 

[Naindejardin]

alpo Hey man I don’t think you went off topic. And I agree you can create a better environment than the outside, I grow medicine as a hobby. If I were to have a larger dedicated space and lots of money I’m sure I could get the perfect environment. Just at this point trying to get the best of my 4x4.

 

[f-e]

LED's can illuminate the plants well beyond any other methods. So much so, that work towards a longer day length is a little lost on me. If I can hit the max DLI in 10 hours, then that's when I would like to sleep. My interest piques again when we talk of an effective 10 hour night though. In regards to a 20 hour cycle. Or anything that's quicker than 24. An idea I just can't shake.


I have not used a 315 but have used ceramic MH of other sizes. They work, but I don't see them as better than a sodium of the same wattage. I think some did better with the 315, instead of a 600, because the 600 was too much for them. We often see people do better with half light and half feed. Simply because it's half as demanding. IMO.

LED has certainly caused people problems. For some it's been amazing, while others went back to sodium. Most are happy though. I think HID lamps have seen their day now. I wouldn't invest heavily