730nm for triggering flowering question.

[Loc Dog]

A long time ago I heard about using 730nm light for 10 minutes before the lights come on, and 10 minutes after the lights go off, to induce stronger flowering.

Is that just for the first 2 weeks of flower, or throughout flowering? Any other advice would also be appreciated.

 

[Can of Bliss]

I read something recently about giving far red just before lights out. I forgot the source, but there was at least anecdotal evidence that 15 min of far red gave the plants the message that it was about to be lights out and photosynthesis should start shutting down. This seems to me to be a positive thing for all stages of growth.
It's on a long list of things I want to experiment with. I hope other people jump in here with better info on the subject.

 

[SB7]

730nm for 10 min at lights out.
420-450nm for 1 hr after the far red ( to reduce the stretching that 730nm induces)
All the way through flowering.
Far Red gives one 2 choices : Keep flowering @ 12hrs and it will finisher early than would normally be expected.
OR flower @ 13.5 hr allow more growth and finish on normal time frame. ( 730nm puts them sleep "instantly" as opposed to the 2 hrs or so they normally take , hence the ability to add day light hours and still flower)
I run CMH primary with LED light bars that consist of 440nm, 660nm and 730nm.
I run 440nm / 660nm all day ( with CMH) ( If I'm growing a real "stretcher" then I just run the 440nm to keep them as short as I can)
1/2 before lights out I quit the 440nm/660nm
I run 730nm for 5min before lights out to 15min after lights out.
I run 440nm for 1.5 hrs after the 730nm to decrease stretch.. and anecdotally it seems to increased resin production...
I have also used 440nm all night ( 12/12) to sex them without actually flowering. ( They show sex but don't' actually go into flowering)
When I have culled males , and stop 440nm , all that "pent up" flowering energy , means they explode into flowering.

It's been fun experimenting with the 3 LED light bars , just to see what happens. ( I use a Tyhpon controller for the LED's)

 

[Loc Dog]

730nm for 10 min at lights out.
420-450nm for 1 hr after the far red ( to reduce the stretching that 730nm induces)
All the way through flowering.
Far Red gives one 2 choices : Keep flowering @ 12hrs and it will finisher early than would normally be expected.
OR flower @ 13.5 hr allow more growth and finish on normal time frame. ( 730nm puts them sleep "instantly" as opposed to the 2 hrs or so they normally take , hence the ability to add day light hours and still flower)
I run CMH primary with LED light bars that consist of 440nm, 660nm and 730nm.
I run 440nm / 660nm all day ( with CMH) ( If I'm growing a real "stretcher" then I just run the 440nm to keep them as short as I can)
1/2 before lights out I quit the 440nm/660nm
I run 730nm for 5min before lights out to 15min after lights out.
I run 440nm for 1.5 hrs after the 730nm to decrease stretch.. and anecdotally it seems to increased resin production...
I have also used 440nm all night ( 12/12) to sex them without actually flowering. ( They show sex but don't' actually go into flowering)
When I have culled males , and stop 440nm , all that "pent up" flowering energy , means they explode into flowering.

It's been fun experimenting with the 3 LED light bars , just to see what happens. ( I use a Tyhpon controller for the LED's)

Thanks for the info!!!! I think it may have been you who originally mentioned the 730nm to me. Did you build your own??

I plan on building lights based on CXB3590's very soon. Do you have any advice? I am basing them on growmau5 videos I have watched. Was thinking 3000K and 80 CRI, think they are CB bin. Have seen one guy attach them to 72" X 5.44" heatsink, to avoid building additional framing for them. Otherwise will use the pin heatsinks.

 

[SB7]

Hi Loc Dog,
I'm sure many folks have mentioned the benefits of 730nm

Yes I did build my own using Luxeon 660's and 440's along with Cree 730's ( a couple of years ago)
I used 1.5" aluminum heat sink in 3 ft lengths, with each section using a equal number of all three LEDs. ( Obviously in a 3 channel setup) As an aside, You don't need much 730nm to have the desired affect.

Next up will be some VERO 29 (7's) COB's as they are arguably the best bang for the buck right now. I'm sure you will enjoy the CREE's . I found I spent so much time waffling back and forth between this LED or that instead of just building it and enjoying the rewards. I like the idea of monster pin heat sinks bolted to frame ( I was looking at the 180mm ones predrilled ,available @ kinglighting ( China)
If I recall the 3500K might be slightly ( and I mean "slightly" better option)
I still like the options that having 3 single wavelength LEDs give me as far a phytochrome manipulation is concerned.

Building your own ? Well opinions are everywhere , but just in case you haven't seen this thread it is excellent and he has just updated it re: VERO 7's and using 3500/4000K as opposed to the usual 3000K
It's a good read.
https://www.icmag.com/ic/showthread.php?t=304279

 

[Loc Dog]

I have a 15 watt 730nm for an 8' X 4' tent. How much 440nm is needed for after light out?

I was just about to order the Cree's, and saw someone mention the Vero 29's and 3500K and 4000K. Was going to use 16 CXB3590's for a 4' X 8' tent, running 800 watts. Are fewer Vero's required for the same size area? Would 2 of these Vero kits be equal to 2 of the Cree kits? I can research, but thought you may know a quick answer -

http://www.cutter.com.au/proddetail.php?prod=cut3097

http://www.cutter.com.au/proddetail.php?prod=cut3122

Spent a month reseaeching the Cree's. Will read your link, and do some additional research. Cutter in Australia seemed to have the best prices for Cree. Is there any vendor you know of for the Vero's that is cheap??

Thanks for the advice!!!!

Do you have any idea where about in that article they discuss the 3500/4000? I have read parts of it before, but it is 130 pages.

 

[Loc Dog]

Someone on another thread said that LED's are not good for flowering, due to no UVB. How many watts of UVB are required per square foot, for resin production???

 

[neverforget4/20]

Someone on another thread said that LED's are not good for flowering, due to no UVB. How many watts of UVB are required per square foot, for resin production???

The effect of UVB on flowering cannabis is not completely known. There's been a bunch of side by sides and there are a few academic papers showing test results on cannabis and other medicinal plants. While there is no question that UVB effects plant responses there isnt consensus that it improves thc% or terpene expression.

In a 4x8 2- 48" agromax pure uv would be adequate. Ive used a few of the various t5s to elicit a UVB response. After a few runs im not sure that its essential.

LED are great for flowering.

HID CFL LED CMH...NONE of these provide much UVB. UVB is blocked by ordinary glass. Special glass is used for UVB emitters.

The "far red thread" over on RIU has good 730nm info.

 

[Loc Dog]

The effect of UVB on flowering cannabis is not completely known. There's been a bunch of side by sides and there are a few academic papers showing test results on cannabis and other medicinal plants. While there is no question that UVB effects plant responses there isnt consensus that it improves thc% or terpene expression.

In a 4x8 2- 48" agromax pure uv would be adequate. Ive used a few of the various t5s to elicit a UVB response. After a few runs im not sure that its essential.

LED are great for flowering.

HID CFL LED CMH...NONE of these provide much UVB. UVB is blocked by ordinary glass. Special glass is used for UVB emitters.

The "far red thread" over on RIU has good 730nm info.

Thanks for the reply. I have been studying LED for a couple of months. Was going to buy Cree CXB3590's, but now Vero 29 Gen 7's are the best bang for buck. I saw someone claim that UVB was critical for resin production today. Have seen some reasonably priced reptile lights, but not much watttage.

Do you know if the side by side experiments were lab tested for potency??

Another question I have, is for a 4 X 8 foot tent, would 8 or 10 Vero 29's be most efficient? Would be running at 90 watts each, so 720 or 900 watt total.

 

[neverforget4/20]

Thanks for the reply. I have been studying LED for a couple of months. Was going to buy Cree CXB3590's, but now Vero 29 Gen 7's are the best bang for buck. I saw someone claim that UVB was critical for resin production today. Have seen some reasonably priced reptile lights, but not much watttage.

Do you know if the side by side experiments were lab tested for potency??

Another question I have, is for a 4 X 8 foot tent, would 8 or 10 Vero 29's be most efficient? Would be running at 90 watts each, so 720 or 900 watt total.

I would suggest reading up at riu. I built 2x cxb3590 a v29 a730 nm bar all with plans acquired at riu.

Running those v29s @90w will require some decent spacing from canopy. Like maybe 20". If you have height restrictions use more cobs ,lower wattage. Dont sweat the uvb until youve got a good rig figured out.

 

[Lazyman]

There's a link in my sig to a really good UVB thread, also used at lights on and lights off, briefly. No people can be in the room during these times though, sunburn city. It is reported that it increases terpene and THC production, as the radiation makes the plant defend itself. However, i would recommend doing this only if you seriously remove fan leaves, you don't want the plant dedicating a lot of its energy into protecting fan leaves.

 

[neverforget4/20]

Someone on another thread said that LED's are not good for flowering, due to no UVB. How many watts of UVB are required per square foot, for resin production???

https://www.icmag.com/ic/showthread.php?t=260046

 

[creativeprocess]

730nm for 10 min at lights out.
420-450nm for 1 hr after the far red ( to reduce the stretching that 730nm induces)
All the way through flowering.
Far Red gives one 2 choices : Keep flowering @ 12hrs and it will finisher early than would normally be expected.
OR flower @ 13.5 hr allow more growth and finish on normal time frame. ( 730nm puts them sleep "instantly" as opposed to the 2 hrs or so they normally take , hence the ability to add day light hours and still flower)
I run CMH primary with LED light bars that consist of 440nm, 660nm and 730nm.
I run 440nm / 660nm all day ( with CMH) ( If I'm growing a real "stretcher" then I just run the 440nm to keep them as short as I can)
1/2 before lights out I quit the 440nm/660nm
I run 730nm for 5min before lights out to 15min after lights out.
I run 440nm for 1.5 hrs after the 730nm to decrease stretch.. and anecdotally it seems to increased resin production...
I have also used 440nm all night ( 12/12) to sex them without actually flowering. ( They show sex but don't' actually go into flowering)
When I have culled males , and stop 440nm , all that "pent up" flowering energy , means they explode into flowering.

It's been fun experimenting with the 3 LED light bars , just to see what happens. ( I use a Tyhpon controller for the LED's)

Thanks for this post,

Only confusing part for me is when you say "1/2 before lights out I quit the 440nm/660nm" <--- you kill all lights for 20 minutes, then start the 730nm for 10 minutes...?

 

[Jhhnn]

The effect of UVB on flowering cannabis is not completely known. There's been a bunch of side by sides and there are a few academic papers showing test results on cannabis and other medicinal plants. While there is no question that UVB effects plant responses there isnt consensus that it improves thc% or terpene expression.

In a 4x8 2- 48" agromax pure uv would be adequate. Ive used a few of the various t5s to elicit a UVB response. After a few runs im not sure that its essential.

LED are great for flowering.

HID CFL LED CMH...NONE of these provide much UVB. UVB is blocked by ordinary glass. Special glass is used for UVB emitters.

The "far red thread" over on RIU has good 730nm info.

If UV were necessary for good resin production we wouldn't be able to grow cannabis worth a damn under any of the commonly used light sources. They put out zip UV, quite by design.

OTOH, there's a lot of salesmen trying to convince growers that only their shit will truly unlock the secrets of the universe...

 

[creativeprocess]

If UV were necessary for good resin production we wouldn't be able to grow cannabis worth a damn under any of the commonly used light sources. They put out zip UV, quite by design.

OTOH, there's a lot of salesmen trying to convince growers that only their shit will truly unlock the secrets of the universe...

your skepticism is definitely appreciated, but I'm leaning more towards the possibility of UV exposure (during the last 2 weeks of flower) enhancing the plant in a variety of good ways, although enhanced THC may not be one of them (let the data confirm or debunk it).

For example,

(e)  UV-B tolerance mechanisms
.... Screening sensitive tissues from UV-B radiation is a secondary option available to plants either to avoid or at least minimise damage. Tissue screening may be achieved through structural modification of organs or by screening molecules which absorb UV radiation. Such features may be either static, as with leaf orientation or phototaxis, or dynamic, as in synthesis of screening molecules which absorb UV radiation in a highly selective way. Screening molecules commonly appear after exposure to UV radiation (Beggs et al. 1986) as secondary metabolites such as flavonoids. Substantial amounts of such pigments accumulate especially in the upper epidermis of leaves. Along with cuticular waxes and other cellular components, these substances attenuate incident UV radiation, and energy transmitted to underlying tissue is decreased by up to two orders of magnitude (Figure 12.19; Beggs et al. 1986). Flavonoid pigments are synthesised by leaves on many plants in direct response to UV radiation. Such photoprotective mechanisms can be likened to tanning responses in humans.

However, Interactions between UV-B radiation and other environ-mental factors are obviously complex and their combined effects on plant responses cannot be predicted from single-factor experiments.

https://plantsinaction.science.uq.e...2-2-3-ultraviolet-radiation-and-plant-biology


However, I think it's a good place to say that most LED manufacter's are producing their diodes to emit UVA wavelengths bewteen 400 nm - 320 nm whereas UVB is much lower, at 320 nm - 290 nm.

So does UVA have similar impacts? I found this research:

"Exposure to UV-A resulted in significant increases in the total ascorbate pool for D. bardawil LL, while D. bardawil HL exhibited smaller, but statistically significant, increases following exposure (Fig. 7). There was no significant change in total ascorbate content for any species following exposure to UV-B. In addition, no change in the total or reduced ascorbate pool was observed for D. salina following exposure to UV-A or UV-B. In all of the samples tested, reduced ascorbate comprised greater than 85% of the total pool.
....
We found that exposure to UV-A irradiance leads to increased formation of reactive oxygen within the chloroplast, as exhibited by the increase in ascorbate peroxidase activity within the cells (Fig. 6A). Following 24 h of exposure to UV-A, the greatest increase in ascorbate peroxidase activity was observed in the high β-carotene cells of D. bardawil. UV-A induced smaller, but statistically significant increases in low β-carotene cells within 24 h. In contrast, UV-B exposure did not produce significant changes in ascorbate peroxidase activity in any cultures (Fig. 6B). Approximately 90% of the ascorbate peroxidase in Chlamydomonas is located within the chloroplast (Takeda et al. 1997). All excess β-carotene accumulation is entirely within the chloroplast, as well, but in an inter-thylakoid location, primarily just inside of the inner envelope (Borowitzka and Borowitzka 1988, Ben-Amotz et al. 1989, Lers et al. 1990). Therefore, the contents of the chloroplast are surrounded by β-carotene globules, but the remainder of cellular contents are not."
https://academic.oup.com/pcp/article/43/8/877/1805632/Contrasting-Effects-of-UV-A-and-UV-B-on
Adding UVA is definitely going to have an effect on the "toughness" of the plant. What that is for everyone's favorite, cannabis, it'll take some unbiased research to determine for certain!