Summary on the influence of UVB-radiation on cannabis

So first of all I want to say that I was very interested in the effects of UV-radiation on plants at all.
So I started to search for information and found many people talking about that topic.

I didn't do any of this by myself, i just collected it and tried to write a summary here.

The thing I found out was there are some believers and deniers.
The believers were relating to a scientific research which had been published in 1987.
the deniers said that this was a one time experiment and the results have never been proved in a second experiment.

So here is a picture of the study so you can search it for yourself.



or follow this link here:
http://smartgrowtechnologies.com/wp-content/uploads/2015/09/UVB-RADIATION.pdf

So in a summary of this experiment you can say that they found out that there is a maximum of 1500 µmol/(m²s) (PPFD) that cannabis can use in terms of growth rate. Higher amounts may result in a lower growth rate.
They also have seen increased THC production on plants that have been radiated with UVB radiation with a peak at 313nm. They radiated them with a daily dose of 13,4 kJ/m². ( 3,72 Wh/m² )
another thing they found out is that CBD isn't affected from UVB radiation. (they showed no data for this but mentioned it in their results)
an important thing they mentioned is that there could be possible other influences that helped to increase the THC production.
Because of this was a one-time experiment and the results haven't been reproduced you could not be sure to this point if it is rly the UVB radiation caused this increased THC production.

So for myself I came to the conclusion that even if it is a one-time experiment there has to be some truth in it. I looked up different absorption spectra was surprised as I saw the following:

Chlorophyll A:



Chlorophyll B:



Carotene:



surprise for carotene at 280 - 285nm peak



Peridinin:



You can see that in light colors of blue and red there is a high amount that's getting absorbed and that's the reason why most LED-Lamps end up with blue and red LED's which when getting mixed look purple.
A proof for this did a scientist called Theodor Wilhelm Engelmann. The experiment he did was to break up a light beam through a prism into the complete PAR spectrum (Photosynthetically Active Radiation, 400nm - 700nm).
Then the broken up light beam radiated on algae sitting in a low amount of a watersolution.
The results were fascinating. He measured the amount of photosynthetic activity in the amount of oxygen produced and found out that the highest productions where at wavelengths of blue and red color.
Here is a pic for your imagination:



However, his experiment was somewhat flawed because he used the sun as his light source. He failed to account for the fact that the sun does not emit all visible wavelengths of light at the same intensity.
Later on further analysis of plant pigments proved that his results were valid.
A year later Engelmann discovered that purple bacteria utilize ultraviolet light in the same way.

So the first thing that came in my mind was “OK so the UV-wavelengths are also absorbed from all, so it has to influence cannabis in a way, which way this ever will be”.

So far so good. so the next thing I wanted to know was, what happens to plants when they get hit by UV-radiation?
Back to some more internet searching I found a scientific research about this topic.

It is called: "Perception of UV-B by the Arabidopsis UVR8 Protein"

You can find it here:
http://science.sciencemag.org/content/332/6025/103
to read the full article u need to complete a free registration.

The summary of this was, that there are so called "UVR8" proteins that work as a UV-photoreceptor.
There are several proteins with different absorption spectra, effects and ways how they are produced. (wavelengths between 280 - 320nm)
These UVR8-proteins work as a defense against UV-radiation. UVR8 is a so called "dimer" which means it is made of 2 structurally similar protein sub units.
They are connected to a so called "Protein of interest" which sits in the surface of the plant. When UV-radiation hits them they break apart and release the Protein of interest.
This protein "tells" the plants to change their behavior.

So here a pic how these UVR8 proteins could be imagined:



and here compared absorption spectra from the different UVR8's:



I wanted to know what these UVR8 are doing to cannabis and what type of behavior change could be expected. So i was back to search the internet. After some time i found a scientific research called "The effect of ultraviolet radiation on the accumulation of medicinal compounds in plants".

This can be found here:
http://faculty.ksu.edu.sa/18856/Articles/The effect of ultraviolet radiation on the accumulation of medicinal compounds in plants.pdf

The summary is, that UV-radiation stress is stimulating the production of chemicals via the phenylpropaniod pathway.
Specifically for malonyl-CoA and phenylalanine. This is important because olivetol is biosynthesized by a reaction from hexanoyl-CoA and three molecules of malonyl-CoA.
Olivetol again is used from the cannabis plant to produce delta-9-tetrahydrocannabinol.

Here is a pic from the study:




This may be something growers can take an advantage from if used correct!

In the next to posts I will go through some theoretical ideas and methods I was thinking about and where you can get this specific needed spectrum from.

So stay tuned.

P.S.: if u find something is wrong please correct me! I didn't do any of this by myself, i just collected it and tried to write a summary here.

" Where to get that spectrum from? "

LED:

Well a lot of ppl maybe say, lets take some LED's for this. I did some research and yes there is a possible way of getting this spectrum from LED's.
But because there is always a but, there is a but here too. These LED's are pretty expensive ( 60 bucks for one ). They consume 200mW/h and produce
20 µW/cm² at a distance of 10 cm. We need to wait for good UVB emitting LED's. Most powerful LED i found at 275nm (MTSM275UV-F1120).


UV-tubes ( 120 cm or 4 Foot . This limitation is because there are a lot of tubes in the 1,76 cm length (5,77 foot).

" AgroMax Pure UV (54W)"

The "AgroMax Pure UV" ( 4 foot F54T5HO Pure UV 54W ) tube.
From the data given on the homepage it emits 440 µW/cm² UV-radiation ( UVB + UVA ) at a distance of 30 cm.
Taking that 75% UVB and 25% UVA data from the homepage you end up with 330 µW/cm² UVB and 110 µW/cm² UVA at a distance of 30 cm.
! Very dangerous !

" Philips UVB Broadband TL 40W/12 RS SLV/25 (40W) "

The bradband 40W tube from Philips ( Product code: 871869666245800 | Google-search brings you to the homepage).
This tube is a medical therapy lamp with a narrow spectrum between 275 nm - 400 nm and a peak at 311nm. The only light output this tube emits is in this
range. The UV-output ( UVB ) is about 4,1 - 4,7 W from the 40W input ( 101V; 0,43A ). The UVB-output at a distance of 10cm is
about 410 - 470 µW/cm²! You see there is a reason why you have to calculate the radiation duration with a doctor for these tubes.
! Very dangerous !

" Philips UV-B Narrowband TL 40W/01 RS (40W) "

The narrowband 40W tube from Philips ( Product code: 871869666239700 | Google-search brings you to the homepage).
This tube is a medical therapy lamp with a narrow spectrum between 305nm - 315nm and a peak at 311nm. The only light output this tube emits is in this
range. The UV-output ( only UVB in this case ) is about 7,5 - 7,7 W from the 40W input ( 104V; 0,43A ). The UVB-output at a distance of 10cm is
about 750 - 770 µW/cm²! You see there is a reason why you have to calculate the radiation duration with a doctor for these tubes.
! Very dangerous !


Reptile-Lamps

Spot-lights

I first tried to take these into my summary but after some research i found out that the coverage of these lamps is pretty bad for "grow" reasons.
They take a lot of power, cover a small area and also got a lot of non UV-radiation in their spectrum. They got very high UV-radiation but small
coverage, this would end in a massive hotspot! So i wont go further into these.

Tubes

" Exo Terra Repti Glo 10.0/T8 or T10 40W "

This is a 40W tube with a spectrum made for reptiles! They say that the UVA-radiation is at about 33% and the UVB-radiation is at about 10%. Sad part
about these is that they arent that powerful on distances further than 50cm. The reason for this is that if there is a higher amount of UV-radiation
that a reptile needs it would get a spot-light. So the reptile tubes are made for constant low levels of UV-radiation and the Spotlights are made for
UV-radiation peaks where the animal can go in and out.

Other tubes with 5 or even 2% UV-radiation would be to bad in terms of UVB output so i wont go further into these.

There could be more tubes in 4 foot length that i am missing! If you know one pls tell me.

---------[ AT - THE - END]---------

In my opinion the " Philips UV-B Narrowband TL 40W/01 RS (40W) " is the "cleanest" way of getting UVB radiation to the plants. It has a pretty narrow
spectrum (305nm - 315nm; peak at 311nm) and about 18,75% UVB-output compared to the 40W input. The useful lifetime is about 9000 hours.

For UVA and UVB the " AgroMax Pure UV (54W)" and the " Philips UVB Broadband TL 40W/12 RS SLV/25 (40W) " are both pretty good. The AgroMax is
the cheaper way of getting UVA and UVB to the plants but its spectrum is not UV-only. So if a more UV-controlled setup is needed i would take
the Philips even if it costs a lot more.

" How not to kill plants with a UV-source? "

As I started this i didn't know that this is a hell of a topic. At I end i just accepted that i don't have to knowledge to calculate precisely.
Also when I calculate the intensity difference I use the formula1: I2 = I1 * (r1/r2)². I could miss something here, maybe it's the wrong formula!
When i did some calculations i mentioned that some companies calculate their values with a different formula. ( formula2 that mostly gets their value
is I2 = ((I1 * ((r1/r2)² + (r1/r2)))/2 )
I will take formula1 for the experiment calculation cause thats where i am more safe about.

So a thing I mentioned was that in all the scientific researches I found ( first post ) they always used a certain amount of UV-radiation.
The amount was measured in kJ/m².

Every information i could collect about the experiment I will list now:

Energy amount: 6,7 or 13,4 kJ/m². This amount of energy has to "hit" the plants, no matter how high the distance is from the lamp to the plants!
Light source: 40W tube peak 313nm. Lengths available for 40W are 60, 90 or 120 cm.
Distance tube to plants: 25 or 35cm
Radiation time: 6 hours a day; for 70 days in total.

I assume the following:

For the energy amount of 6,7 kJ/m² they radiated over a time of 6 hours at a distance of 25 cm. [Example A]
for the energy amount of 13,4 kJ/m² they radiated over a time of 6 hours at a distance of 35 cm. [Example B]

All converted:
6,7 kJ/m² = 6700 Ws/m² = 0,67 J/cm² = 0,67 Ws/cm² = 1,861 Wh/m² = 186,1 µWh/cm²
13,4 kJ/m² = 13400 Ws/m² = 1,34 J/cm² = 1,34 Ws/cm² = 3,722 Wh/m² = 372,2 µWh/cm²

[Example A]
1,861 Wh/m² = 6h * X W/m². X = 0,3102 W/m².
Converted: 31,02 µW/cm² that has to be delivered from the light source to the plants over 6 hours at 25 cm distance.

I assume the reflector tightens the beam to a 125,5 degree angle. ( at a distance of 25 cm that's 83,33 cm width for the 120 cm long tube = 1 square meter)
I also assume that no light is lost in terms of hitting the plants. ( every beam hits the plants directly or over the reflector with 100% effectiveness which is impossible )

Calculating back from the 31,02µW/cm² when the lights in the experiment took 6 hours at a distance of 25 cm for 6,7 kJ/m², there has to be 192,875 µW/cm² (1,93875 W/m²) at a distance of 10 cm .

[Example B]
3,722 Wh/m² = 6h * X W/m². X = 0,6203 W/m².
Converted: 62,03 µW/cm² at 35 cm distance that has to be delivered from the light source to the plants over 6 hours.

I assume the reflector tightens the beam to a 114,5 degree angle. ( at a distance of 35 cm that's 83,33 cm width for the 120 cm long tube = 1 square meter)
I also assume that no light is lost in terms of hitting the plants. ( every beam hits the plants directly or over the reflector with 100% effectiveness which is impossible )

Calculating back from the 62,03 µW/cm² when the lights in the experiment took 6 hours at a distance of 25 cm for 6,7 kJ/m², there has to be 759,8675 µW/cm² (7,598675 W/m²) at a distance of 10 cm .

OK perfect now I know all I need to do it the same way like they did in the experiment.




" How I would do it? "

Let's say I got a 1,2 x 0,9 m tent and my light is in a distance of about 50 cm.

"AgroMax - Version "

AgroMax is one of the companies that calculate their intensities with the formula2 i mentioned at the beginning of this post.

The "AgroMax Pure UV" ( 4 foot F54T5HO Pure UV 54W ) tube.
From the data given on the homepage it emits 440 µW/cm² UV-radiation ( UVB + UVA ) at a distance of 30 cm.
Taking that 75% UVB and 25% UVA data from the homepage you end up with 330 µW/cm² UVB and 110 µW/cm² UVA at a distance of 30 cm.
This tube would need only about 26 minutes for a dose of 6,7 kJ/m² UVB-radiation at a distance of 25 cm [Example A] !VERY DANGEROUS! )
So if I increase the distance from the tube to the plants to the distance of the normal light at about 50cm the intensity would be 1,584 W/m² (158,4 µW/cm² UVB-radiation )! That would be only 2 hours and about 20 mins a day for the dose of 13,4 kJ/m². [Example B]

Since this tube is so powerful ( i never tried it but even the worst case of my theory is very powerful )I would take that 2 hours and 20 mins and hope that my result (158,4 µW/cm²) is way too much over the real result. ( after tests the duration can be increased or maybe decreased )

I would divide that 140 mins by 7 to end up with 20 minute doses with 1 dose per hour. ( half the dose would be 10 min per hour, full dose would be 140 min duration ).


" Philips UV-B Narrowband - Version "

The " Philips UV-B Narrowband TL 40W/01 RS (40W) " tube.
From the data given on the homepage it emits 750 - 770 µW/cm² UV-radiation ( UVB ) at a distance of 10 cm.
This tube would need only about 52 minutes for a dose of 6,7 kJ/m² UVB-radiation at a distance of 25 cm [Example A] !VERY DANGEROUS! )
So if I increase the distance from the tube to the plants to the distance of the normal light at about 50cm the intensity would be about 0,308 W/m² (30,8 µW/cm² UVB-radiation )! That would be 12 hours and about 5 mins a day for the dose of 13,4 kJ/m². [Example B]

I would do 1 block of 12 hours or 2 blocks of 6 hours. In worst case 3 blocks of 4 hours or even 4 blocks of 3 hours.

Daily cycles in theory:


The daily light cycle would look like this: ( "The gentle one" )

Up to 3 weeks old:
No UV-radiation!

About 3 weeks old and looking healthy:
half the calculated dose per day

1st day of flower:
full calculated dose per day


Another daily light cycle would look like this: ( "They like it rough" )

Up to 3 weeks old:
No UV-radiation!

About 3 weeks old and looking healthy:
full calculated dose per day

1st day of flower:
full calculated dose per day


The daily light cycle would look like this: ( "Fck it, lets try the max!")

Up to 2 weeks old:
No UV-radiation!

About 2 weeks old and looking healthy:
full calculated dose per day

1st day of flower:
full calculated dose per day


If I need to work till the tubes will be turned on and to avoid changing the daily light schedule
- I would set an alarm clock for 10 minutes before they get turned on to avoid running into UV-radiation without protection.
- I would set another alarm clock for 5 mins before they get turned on so I can't forget to get my protections on. ( You know why )

Plant hitting UVB-radiation-energy ( all emitted wavelengths together, or better said full spectrum of the light source ) needs to be about 370 µW/cm² daily dosis.
So if u want to buy a light source, most of them measure their lights in µW/cm² at 4,8,12... inch distance. To hang the light at a distance of 25 cm a UV-output of 116,19 µW/cm² @ 10cm or 4 inches is needed for 6,7 kJ/m² in 6 hours a day! Keep in mind when u search for light sources.

Again! This is just in theory! I never tried any of this in real life so I could be terribly wrong!

For some testing reasons i ordered a "AgroMax pure uv T5" tube and it arrived today.

Gonna take some pics and upload them.

l0wbob2016 said:

For some testing reasons i ordered a "AgroMax pure uv T5" tube and it arrived today.

Gonna take some pics and upload them.

Click to expand...

Be VERY careful with that bulb !!!!

RM3 said:

Be VERY careful with that bulb !!!!

Click to expand...

Yeah i will! also if u read the "calculation" part u know i wont go closer than 50cm ( about 20 inch ).
This tube was alrdy !VERY DANGEROUS! in my calculations so in RL i wont fool around with this one!

Good info.
What do you thinking the Hortrilux Power Veg bulb as a safer alternative?
It's a full spectrum UV bulb.
Used them In veg for awhile.

Hybridway said:

Good info.
What do you thinking the Hortrilux Power Veg bulb as a safer alternative?
It's a full spectrum UV bulb.
Used them In veg for awhile.

Click to expand...

i also found this tube while doing my searches. since it is a mixed spectrum tube ( UV + another spectrum ) i didnt go into it because i just wanted to write about light sources that emit UV-spectrum only ( or close to only UV ).

For me the spectrum looks like a UVB tube with a peak at 311nm combined with a UVA tube with peaks at ~340nm and 365nm combined with a special spectrum from a normal T5 tube.
Sadly there is no information about the intensity of UVA / UVB radiation on certain distance. It is a 54W tube. Let's assume the output has to be divided by UVB-output, UVA-output and rest-spectrum-output. For me it looks like its about 35% UVB, 45% UVA and about 20% goes into the "special"-spectrum. ( relative energy output ).

If i am close to the reality than i think this tube was made for letting it radiate UV-radiation the complete light cycle. This looks for me more like a supporter tube with extra UV-( A & B ).
Like the name says it was made for VEG. So using it in Flower ( where UV radiation has more influence ) would change your flower spectrum. I am not sure if radiating the plants with UV-radiation in VEG-state only has that much influence on the end product.

are these type bulbs any more dangerous than exposure to the tanning booth bulbs shining on unprotected body parts inches away for extended periods of time?

I've used the AgroMax Pure UVB bulbs for a year, 6 intervals of 15 minutes a day, hung about 3 feet above the canopy about 4 feet apart. You don't want to be in the room when these are on. Also, they will damage tender growth that has not been exposed to UVB. This is a problem if you are running a perpetual. The Hortilux Power Veg are excellent for veg, but they don't put out enough radiation for flower. I've also used the Reptile bulbs. Theyse have less range and wear out faster than the AgroMax bulbs, but will do the job if you place them close to the canopy.

chemphlegm said:

are these type bulbs any more dangerous than exposure to the tanning booth bulbs shining on unprotected body parts inches away for extended periods of time?

Click to expand...

the "hardest" UV-radiation tube for tanning i found had 2,5% UVB for a 6 feet 100W tube. Tanning tubes are made for small distances and therefore they cant have such a high output of UVB-radiation than a UV-tube which has been made for growing and big coverage.

You would need to use a lot of them to get the intensity of UVB you want. Also another thing is you dont know the spectrum and its peaks. There is little to no information about intensity at distances over 10 inch away so i think you would need to test it by urself.

olekingkole said:

I've used the AgroMax Pure UVB bulbs for a year, 6 intervals of 15 minutes a day, hung about 3 feet above the canopy about 4 feet apart. You don't want to be in the room when these are on. Also, they will damage tender growth that has not been exposed to UVB. This is a problem if you are running a perpetual. The Hortilux Power Veg are excellent for veg, but they don't put out enough radiation for flower. I've also used the Reptile bulbs. Theyse have less range and wear out faster than the AgroMax bulbs, but will do the job if you place them close to the canopy.

Click to expand...

Is there a reason why you do 6 intervals of 15 minutes ? why not 10 intervals? or why not 20 mins a interval? would be very interested if you did some testings and found out that this works best for you?!

I have found good results using UVA (335-400nm) at low levels (~15w led) throughout the light period as supplemental lighting.

It also keeps pests at bay since it is the same light used in bug zappers.

l0wbob2016 said:

i also found this tube while doing my searches. since it is a mixed spectrum tube ( UV + another spectrum ) i didnt go into it because i just wanted to write about light sources that emit UV-spectrum only ( or close to only UV ).

For me the spectrum looks like a UVB tube with a peak at 311nm combined with a UVA tube with peaks at ~340nm and 365nm combined with a special spectrum from a normal T5 tube.
Sadly there is no information about the intensity of UVA / UVB radiation on certain distance. It is a 54W tube. Let's assume the output has to be divided by UVB-output, UVA-output and rest-spectrum-output. For me it looks like its about 35% UVB, 45% UVA and about 20% goes into the "special"-spectrum. ( relative energy output ).

If i am close to the reality than i think this tube was made for letting it radiate UV-radiation the complete light cycle. This looks for me more like a supporter tube with extra UV-( A & B ).
Like the name says it was made for VEG. So using it in Flower ( where UV radiation has more influence ) would change your flower spectrum. I am not sure if radiating the plants with UV-radiation in VEG-state only has that much influence on the end product.

Click to expand...

It does make a difference in the end veg product. I'd imagine it would have the same type of positive effects in flower w/ some increases in THC as well as leaf mass n thickness. They work well in veg.
I know it doesn't hurt the plants even ran close & for 18hr veg days.

The estimate of 140 total minutes for Agromax seems right. How you break it up doesn't matter much, but I would break it up just to avoid any risk of burning the plants. I only run the bulbs the last few weeks of flower, starting out low, then increasing the total minutes. I don't think the UVB helps yield at all. In fact its a negative. So it;s better to wait till the end of the cycle. You don't need to be so careful with UVA. My setup includes a few LEC's with Philips bulbs for UVA. These can run full cycle.