UVb an experiment

[oldmac]

Quick background: I have been using UVb supplemental lighting for many years now and have always thought it added to the finished product in a couple of ways. I had never promoted it's use on these boards because I felt it was dangerous and had real potential to harm people. That changed a few months back on the other UVb thread, and I came out of the closet in strong support of it's use. Well some here who's opinion I respect (like Weezard) held the opposite view and those discussions led me to the fact I had not done any experiments in a long time trying to compare it's effects.

So I decided to do back to back runs, with and without and to try to see, observe and quantify the differences. I decided to use my personal grow to do this since it is well dialed in and consistent, and I have been using UVb as supplemental lighting. The other grow I'm involved in, I could not seperate some UVb in the bloom room cause of it being built into some lights, like the TI problooms.

Strain is WhiteRhino, grown as SOG size plants (finish @ abt 18" tall) in 4" RW delta blocks in a GI Grow rotating garden. The light source is a homemade LED/T5 hybred; the LEDs consist of 240 red (635nm) Cree's driven at 650ma giving 1.75w/ea for a total of 420 watts and 8 2700K 2' T5s overdriven to VHO levels of 40w/ea for a total of 320 watts. All together it's 740 watts of light, plus power supplies and fluro ballasts. All of this is mounted on a 4" octogon aluminum extrusion and mounted inside a 6" boroscilicate glass tube that is ducted for air cooling. There should be no UVb transmitted thru the glass, if there is any from the T5s.

I started this last run with out UVb on June 7th (full moon) and today marks the 7th week (lost 2 grow days to power outage) they have been in flower.

Early observation:

1) I have always claimed that UVb adds to trichome production, but I have not seen a difference w/o UVb. The WR packed on the tric's just like before, much like white strains do, tric's solid on buds and leaves, some trying to grow on top of each other, often thought it was UVb but it's not. Based on this, and something I've seen in the other grow I must admit trichome production is more a product of genetic predisposition then UVb light influence. My first sorta surprise.

2) Second surprise (big one) is the leaves of the plant in this run are paper thin in comparison to previous runs. W/ UVb the leaves are much fatter and tougher, a very noticable difference. I don't recall reading anything about this, but it looks like UVb adds to the overall plant mass.

3) At this point of 7wks, I would expect to see trichome's that where clear with maybe 25% turning cloudy. Tric's are currently all clear, did lose 2 days so maybe that's the difference, not sure at this time.

So that's where I'm at right now, everyone is welcome to hang out while I wait and see what happens over the last week or so and I get to final finish and a taste test. Question or comments on or off topic are always welcomed even encouraged.

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oldmac Reviewed by oldmac on 07-28-2009. UVb an experiment Quick background: I have been using UVb supplemental lighting for many years now and have always thought it added to the finished product in a couple of ways. I had never promoted it's use on these boards because I felt it was dangerous and had real potential to harm people. That changed a few months back on the other UVb thread, and I came out of the closet in strong support of it's use. Well some here who's opinion I respect (like Weezard) held the opposite view and those discussions led me Rating: 5

[Dogznova]

Oldmac you have noticed some very interesting info on uv-b that IMO should be talked about..
This should be a great tread.. I think I know why your plants are ripening a little slower without uv-b.. Give me a little wile and I will post my reasoning LOL.. Great tread..:thumbsup:

[Dogznova]

Oldmac it's not the uv-b that is making your plants rippin faster it's the blue light associated with the uv bulb you are using. Let me explain.

Most of the cfl type of uv bulbs from (pet stores) omit in the low 300nm to about 400nm BLUE range. That low blue nm range has a fast Time Factor associated with it. So when you add let's say 3 hours of that fast blue nm light to your existing 12 hours of day light you are actually lowering your lights overall 12 hour Time Factor. If your current combined lights Time Factor was say at 4 (just an example) before you added the 3 hours of the fast 300nm to 400nm blue to the mix, now your lights overall 12 hour Time Factor will be around 3.8 ish or lower (just an example) but you get the point. The faster Time Factor day after day will speed up the flowering over time. The truth is.... Speed is one of the only good thing those bulbs offer and it's actually just the Blue 300nm to 400nm that has the speed. Also it's the blue spectrum that makes the leafs,stalks thicker not the uv-b. If you remove the uv from those bulbs and just use them as speed and a blue light source then they are ok. But if your using led's and T5's as your light source then chances are you don't want the thicker leaves because of light penetration issues. Light penetration issues will cause lower THC production by default. So the less blue the better if you don't want to produce thick leaves. IMO

Personally I get most of my speed from far red. Far red has the fastest Time Factor for plants but gives no useful bulk and will cause stretch in the early part of flowering. The strain I work with only likes the low fast Blue nm in the first two weeks of flowering and I like to use 420nm. Not much uv in these lights but good speed.. Any longer then two weeks and the added blue starts to make the flowers way too leafy for me.... But the blue helps keeps the early flowering stretch down and the speed up (red 630nm to 660nm will also keep strech down BUT the speed (time factor) is to slooooow for me)...

My point is.... When everyone figures out that speed (300nm to 400nm) is the only thing good about these lights. The next step will be seeing that the good (speed) don't out way the bad (uv-b). There are much better ways of getting the plants clock moving faster IMO.

More to come soon. :thumbsup:

[crabbyback]

This looks like fun. I'm in.

[oldmac]

Hey Dodznova,

I've seen you martain-nite growers, most recently SalMayo reference the time factor of various lights. I have not been able to find anything about it in the science literature dealing with it...but I'm still looking.

The T5's at 2700K have seemed to be about the same as the full spectrum T5s they replaced, they produce a fair amount of blue and it is the only source of blue present. I need to look at a spectrum graph to see what the T5s produce tho. Orignally this light was to be red leds and whites but the white LEDs I got did not output any usable blue and they failed. I backed into using T5s with just red LED and they worked great, and is why I've tried other Led/T5 combos. The current TI pro-blooms/T5 in my partnered grow have not been successfull, not enough mixing of the lights; center sees only LED outer rows just T5 and only some mixing in between. Plus the pro-blooms are pretty complete on thier own.

Interesting, look forward to further this discussion.

[oldmac]

This looks like fun. I'm in.

Always glad to see you Crabby. This is a fun experiment to me, falls into a "shit & giggles" type of thing, got nothing to really lose by trying it. (or not trying UVb)
It is going to push me back to light theory 101 and make me start to look at wavelenghts again, just what I need as I design another light.

[Weezard]

Always glad to see you Crabby. This is a fun experiment to me, falls into a "shit & giggles" type of thing, got nothing to really lose by trying it. (or not trying UVb)
It is going to push me back to light theory 101 and make me start to look at wavelenghts again, just what I need as I design another light.

Beeg Mahalo fo' dis, OM.

1) I have always claimed that UVb adds to trichome production, but I have not seen a difference w/o UVb. The WR packed on the tric's just like before, much like white strains do, tric's solid on buds and leaves, some trying to grow on top of each other, often thought it was UVb but it's not. Based on this, and something I've seen in the other grow I must admit trichome production is more a product of genetic predisposition then UVb light influence. My first sorta surprise.

Surprised me too, at first. Then I got to thinking about it.

2) Second surprise (big one) is the leaves of the plant in this run are paper thin in comparison to previous runs. W/ UVb the leaves are much fatter and tougher, a very noticable difference. I don't recall reading anything about this, but it looks like UVb adds to the overall plant mass.


As for the thick leaves, I'll dig up the reference for ya, but basically the disk shaped cells that process light lay flat in low light to gather enough energy.

When overlit, or UV cooked, they turn edge-on to the light to present a lower surface area and that's what "thickens" the leaf.
Pretty neat actually.

Nudder week or two for da bake-off.
Unless UVb has a very positive catalytic effect on potency, I'm done with it, yah?

I'm bettin' that the dark spell did set you back about twice as long as it actually lasted.

Also, I found that my buds are ripe when mostly cloudy under leds.
Rusty trichs are few and far between without shortwave radiation damage.
My first led harvest got senile while I waited for the dang amber.

Mahalo again for helping us sort this out.

Weezard

[oldmac]

Yo' weezard, I ain't done with 'ya yet. This experiment is not concluded plus I might need your thoughts on light wavelenghts.

As to a two day set back, I believe that's all there is, they still got battery backup fluros (12v dc camping lights) plus my far red incandescent trigger lights. So thier schedule was not disrupted at all, just not enought light to grow for those two days.

I found some info on the leaf thickening, a result of UVb for sure. But in this case they are flowering in a rotating garden and the plant auxins are screwed up, so the plants don't know which way is up or which direction the light is so I don't think it's the leaves turning edgewise to the light.

As of last nite, trichomes are abt 20% cloudy the rest are clear. So at least that's heading in the right direction.

[Weezard]

Yo' weezard, I ain't done with 'ya yet. This experiment is not concluded plus I might need your thoughts on light wavelenghts.

Anyway I can be of service, do not be shy.

As to a two day set back, I believe that's all there is, they still got battery backup fluros (12v dc camping lights) plus my far red incandescent trigger lights. So thier schedule was not disrupted at all, just not enought light to grow for those two days.

I found some info on the leaf thickening, a result of UVb for sure. But in this case they are flowering in a rotating garden and the plant auxins are screwed up, so the plants don't know which way is up or which direction the light is so I don't think it's the leaves turning edgewise to the light.

You missed me, my friend.
This effect has naught to do with the leaves themselves.

This "edging" happens on a cellular level.
The microscopic thingies that process light within the cells are shaped like disks, lots of them.
When light is weak, they lay flat to absorb more of it.
Then, the leaf feels thin.

When the light is too strong, or a danger, these disk shaped cells slide into a "rool-of-coins" shape that presents only the edge of the cells and protects them from damage, but this makes the leaves feel thicker.

I'm way too baked to even search for the original paper that details this effect.
When I'm able, I'll dig it up for you.
It's a fascinating read and one of the things that made me question the value of UVb for Cannabis.

As of last nite, trichomes are abt 20% cloudy the rest are clear. So at least that's heading in the right direction.

Added some snaps to my album that you might enjoy.
Couple led grown "droolers".

Aloha, OM

Weeze

[Weezard]

A Granum of Thylakoid disks is what I meant to say.
[attachment=o224527]
See;

Photosynthesis 1

For more fun stuff.

Nonsense!
Least I could do!

Aloha,
Weeze