UV light or photoinhibition

BobCajun

BobCajun

Well-Known Member
Greenthumbs21 said:
Thats your problem. ... keep them within a foot... i keep them at 6 inches and move them around
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I guess I'll have to work on getting them that close then. They are just little 13w bulbs after all. You couldn't even grow a plant with a warm white of that wattage with it being more than a few inches away, so it makes sense that it's the same for UV bulbs.
 
Greenthumbs21

Greenthumbs21

Well-Known Member
BobCajun said:
I guess I'll have to work on getting them that close then. They are just little 13w bulbs after all. You couldn't even grow a plant with a warm white of that wattage with it being more than a few inches away, so it makes sense that it's the same for UV bulbs.
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The 26 watter work much better but ya same principle... CLOSE
 
T

The Nine

Active Member
BobCajun said:
That's UV-C, deadly to all life. If you click on the replacement tube it tells you about it.
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That's why I said intermittently. Would this not kick the plants defence mechanism ( thc production) into high gear for the last 2 weeks say on for a few mins every hour as the plant tries to stay alive for pollination?
I'm just asking questions here mate, not claiming any thing, we are all searching for better methods/techniques.
 
T

The Nine

Active Member
Greenthumbs21 said:
View attachment 3621908
It goes uva..uvb..uvc..xray..gamma ray. UvB is as low as you want to go for skin and plants.
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I certainly wouldn't be in the room/tent whilst they were running and I think using good quality extract to quickly remove the o3 that these generators produce will limit the harm.
I will wait and see if anyone else has tried this, this forum is a wealth of information of peoples experimentations with the sacred plant. :)
 
BobCajun

BobCajun

Well-Known Member
The Nine said:
That's why I said intermittently. Would this not kick the plants defence mechanism ( thc production) into high gear for the last 2 weeks say on for a few mins every hour as the plant tries to stay alive for pollination?
I'm just asking questions here mate, not claiming any thing, we are all searching for better methods/techniques.
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The UV light band used by cannabis to produce more phenolic compounds (which lead to THC) is 290 nm. Anything below that would be useless and incredibly dangerous and harmful. No living thing can take UVC, fortunately the ozone layer filters it all out of sunlight.
 
Rayne

Rayne

Well-Known Member
~CReePeR~ said:
How should UVB be run during a grow, 1) from start to harvest 2) from start of flower cycle to harvest or 3) 2-4 weeks into flower cycle (depending on length of cycle) to harvest?
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If you haven't added UV A/B supplementation in a previous grow just added one or two lights (T-5 or cfl) to your current grow at whatever stage your are at. Don't wait for "Peer" review to try something.

For the individual who are savvy enough, the fact that UV A/B is produced by the sun aught to be enough reason to use UV A/B in an indoor grow season.

My current grow, has had UV A/B supplementation since the beginning stages.

For those who grow for "Hash" production...yield increases. For those who grow for flower production...yield stay about the same.
 
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BobCajun

BobCajun

Well-Known Member
Rayne said:
If you haven't added UV A/B supplementation in a previous grow just added one or two lights (T-5 or cfl) to your current grow at whatever stage your are at. Don't wait for "Peer" review to try something.

For the individual who are savvy enough, the fact that UV A/B is produced by the sun aught to be enough reason to use UV A/B in an indoor grow season.

My current grow, has had UV A/B supplementation since the beginning stages.

For those who grow for "Hash" production...yield increases. For those who grow for flower production...yield stay about the same.
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But you must also consider the fact that UV reduces growth. It's sort of a tradeoff, you can either have maximum growth and weight yield but with lower secondary plant products like THC, or the other way around. Maybe cannabis can take UV more than the other plants in the studies, IDK, but it's probably pretty similar.
 
Rayne

Rayne

Well-Known Member
BobCajun said:
But you must also consider the fact that UV reduces growth. It's sort of a tradeoff, you can either have maximum growth and weight yield but with lower secondary plant products like THC, or the other way around. Maybe cannabis can take UV more than the other plants in the studies, IDK, but it's probably pretty similar.
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If you want the plant to develop to it's fullest genetic potiential. UV A/B light and Infrared light must be included.

Outdoor Sativa strains get bathed in UV A/B plus infrared red and still grow at least 10 foot tall.
 
T

The Nine

Active Member
BobCajun said:
The UV light band used by cannabis to produce more phenolic compounds (which lead to THC) is 290 nm. Anything below that would be useless and incredibly dangerous and harmful. No living thing can take UVC, fortunately the ozone layer filters it all out of sunlight.
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Thanks

I found this on another forum
Excellent response and a lot of good information. You definitely make the point that UV-C is not to be used without a complete understanding of the handling and dosing of this spectrum. I generally agree with everything put forth but would like to point out some mischaracterizations regarding the way power and energy have been discussed for the purposes of using UV-C for plant sterilization.

Powdery mildew requires around 1800 u watts of uvc to kill the spore. On an 11 watt uvc bulb that means a quick once over with the lamp will kill all spores the light falls on.

The proper specification for a dose is total Energy per an area. This specification is given in uWatts which is Power (Energy/Time) not Energy and also lacks the Area it is applied to. The copy and paste is incorrect in that it is mixing up Power with Energy. My best guess is that the author intended this value to be 1800 uJoules/cm2.

Good daily short term use not only kills spores but actually helps the plant to develop thicker leaves which again helps to combat pathogens.

Uvc really is the way forward for desease control.

Here is a copy and paste from another site...
.........

Ultraviolt light (UV) occurs from the sun. The wavelength of UV is outside of our visible range. The lowest wavelength colour we can see is violet, hence the name for light with a wavelength lower than this is ultraviolet.

UV ranges from 100 nanometres to 400nm. UV is further divided into UV-A, UV-B and UV-C.
UV-C: ranges from 100nm – 280nm (germicidal)
UV-B: ranges from 280nm- 315nm (sunburn)
UV-A: ranges from 315nm – 400nm (blacklight)

We here are interested in the UV-C rays, also known as „short wave ultraviolet radiation“. UV-C`s germicidal properties have been known since the 1930s. They are used in labratories in order to destroy bacteria, mould and viruses. UV-C rays are able to penetrate the outer membrane of microbes and stop them from reproducing. The specific wavelength of 253,7 nm is known to break the DNA of pathogens.

Germicidal UV sterilization is optimal at 260nm and good results are generally achieved in the 240 to 280 nm range. What is special about 253.7nm is that it is very close to the 260nm optimal, but more important it is easily produced since it is the primary quantum emission for Mercury.

In May 2007, two Dutch inventors, Arne Aiking and Frank Verheijen were granted an International Patent on a method of treating live plants and mushrooms against pathogens with UV-C light. In the past UV-C had only been used to sterilise things like air and water. The difference with proposing to use UV-C to fight pathogens on living plants is that you shouldn`t use any more than is necessary, otherwise there is a risk to health of the plant.

Mr. Aiking and Verheijens invention is a mobile UV-C lamp that travels up and down in commercial greenhouses. The light intensity of a UV-C germicidal light bulb is usually expressed in a term called „microwatts per square centimetre“. Mr. Aiking and Verheijen suggest a range between 2,500 and 150,000 mircrowatts of UV-C energy over a given 24 hour period.

Once again they are mixing up Power and Energy, Watt or uWatt is a Power term which is a rate of Energy transfer (Watt = Joules/Sec). Joules is the Energy term generally associated with Watts (Joule = Watt x Sec). With the exception of the 100 Watt UV-C lamp all of the values given below should be changed from W (Watts) to J (Joules).

The easiest analogy to make to this difference between Power and Engergy is the way the Power Company charges us. We are most familiar with Power as the quantitative term for our electricity, but the power company charges us based on kWatt-Hours. A kWatt is 1000 Watts, but Watts is a Power measurement which is a Rate of Energy Transfer. To get Energy we must multiply this rate by the time for which it is applied, thus Energy = Power x Time. This is why the power company charges us based on kWatt-Hours, kWatt being the power term, Hours being time and the product is actual Energy (kWatt-Hour).

E.g. A 100 Watt UV-C lamp will output approximately 14,000 microwatts of energy over a square centimetre, in one second, from a distance of two centimetres away. If we leave it there for one minute we have to multiply that figure by 60. (840,000 microwatts). Look at the following chart:
1cm 21,000 µW/cm2 UV output
2cm 14,000 µW/cm²
3cm 10,000 µW/cm²
4cm 8,000 µW/cm²
5cm 6,700 µW/cm²
…
100cm 360 µW/cm²

This shows that a second`s exposure at 1cm distance is roughly equivalent to a full minute`s exposure 1 meter away (360 x 60 = 21. 600µW/cm²).

We use the UV-C light to fight against powdery mildew in our plantation. Tests have shown that powdery mildew is killed when given a dose of 1720 µW of UV-C per square cm. For exemple if I took a 100 Watt UV-C lamp and positioned it two centimetres away from the mildew, I would need to switch on the UV-C lamp for just 1/10 of a second to kill it.

Spider mites could possibly also be effectively treated with UV-C but with amounts that are hundreds of times more compared to something like powdery mildew. We therefore use it only against powdery mildew.

The safest way to use UV-C on plants appears to be regular, smaller doses rather than a single, lager hit. We therefore use the UV-C light every day for a short time. The pathogen must be hit directly with the UV-C rays in order to be affected. If it is protected by a leaf, the UV-C will not be effective, because UV-C will not penetrate through leaves.

WARNINGS:
UV-C light has an intense burning effect on human skin and can quickly damage your eyes.
Protect your eyes with special eyeglasses
Don`t expose your skin to UV-C rays
The wrong amount of UV-C will damage your plant
This topic is part of one of our next episodes on FlowerfieldTV. We have just started the treatment of our plants with UV-C rays. At the moment we also use sulphur, because we don`t run the risk of getting powdery mildew. After that stage will treat our plants exclusively with UV-C ray. We will regularly report our experiences and tell you our improvements in This thread.

As these warnings indicate, the use of UV-C is not for the uninitiated and should be applied very carefully
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BobCajun

BobCajun

Well-Known Member
The Nine said:
Thanks

I found this on another forum
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It might be okay in an automated light moving system, but I wouldn't use the handheld ones. The amount of microwatts put out is huge at close distance. Your entire body would have to be covered and you'd need special goggles. Just not worth it to kill powdery mildew. UVB is dangerous enough, don't even think about UVC unless it's in a completely enclosed area like a sterilizing cabinet.
 
T

The Nine

Active Member
BobCajun said:
It might be okay in an automated light moving system, but I wouldn't use the handheld ones. The amount of microwatts put out is huge at close distance. Your entire body would have to be covered and you'd need special goggles. Just not worth it to kill powdery mildew. UVB is dangerous enough, don't even think about UVC unless it's in a completely enclosed area like a sterilizing cabinet.
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Thanks again mate :)
I hear you, and you are makng sense.
 
DankaDank

DankaDank

Well-Known Member
Im a bit conflicted regarding this topic, this reddit thread seems to make sense https://www.reddit.com/r/Head2HeadMG/comments/2nt3ml/red_white_blue_full_spectrum_an_led_color_choice/
but then there's this
http://medicalmarijuanagrowing.blogspot.co.uk/ wich is apparently an actual test (just read from the third page and scip the mildew shit).
The dankest strains do come from high altitude areas so could it be more uv or simply more light or even different atmospheric conditions and lower altitude areas seem to have more cbd rich strains, so maybe uva and b are detrimental to cbd ,so many questions and so little tests better get my shit together and start some test journals :joint::bigjoint:
 
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