The spectrum of (PAR) may be important to reduce destructive effects of UV radiation

[Bubbleblower]

Just to point out, there is nothing in what you quoted, nor what I quoted, that is different than anything anyone has been writing in this thread with respect to mitigating UV-B damage.

Indeed, but it sure doesn't come across that way and people (not) reading this will have the impression UVA isn't important at all and my statements about that were wrong. They'll just add the UVB and think they are fine.

Yes, as well as other science (published research) I didn’t cite. .

Please cite it, I am very interested. If you can't find it just give me your math.

the MegaRay UV-B lamp
.

These kind of lamps can decay by more than 50% in the first 100 hours. And also:

It's a basking lamp with an extremely small footprint, very bad for growing cannabis.

(specialty narrow-band medical grade lumiaires). using a lab grade UV-B lamps setup.

So you will be using narrowband UVB?

 

[Beta Test Team]

Just to point out, there is nothing in what you quoted, nor what I quoted, that is different than anything anyone has been writing in this thread with respect to mitigating UV-B damage.

Indeed, but it sure doesn't come across that way and people (not) reading this will have the impression UVA isn't important at all and my statements about that were wrong. They'll just add the UVB and think they are fine.

I disagree completely. I and others (including you) wrote that UV-A (and PAR) is used by plants to mitigate UV-B damage.

Honestly, it seems like in your posts to me you're trying to be "right," like you're trying to score points or something, as if you’re trying to prove what I’m writing is wrong to make your points look more correct. That’s why I’m less than enthused when I post to you.

It's like you see it as an "us" vs. "you" type of thing. And it's not. All that matters is science and being able to backup claims made. If you’re wrong (and you have been) that's not a bad thing, just like it's not bad when I'm wrong (as happens often! ).

UV-A in the order of 5 to 10 times (or greater) than the PFD (photon flux density) of UV-B is a good goal as well

How did you arrive at that conclusion (math)?

Yes, as well as other science (published research) I didn’t cite. .

Please cite it, I am very interested. If you can't find it just give me your math.

The math is simple, just look at a SPD of the sun near solar noon and it's easy to calculate. Again, these are ballpark figures, there is no hard data to cite as ideal (at least we know of).

And as I pointed out on the first page, most UV-B lamps will have sufficient UV-A. Most UV-B lamps emit more UV-A than UV-B (other than specialty narrow-band medical grade lumiaires or LEDs). For example, one of the most highly regarded UV-B lamp brands by herpetologists is the MegaRay UV-B lamp, and here are its specs: a 1:6 to 1:8 ratio of UV-B to UV-A, or put another way, about 11% to 14.25% of the UV light emitted is UV-B:

These kind of lamps can decay by more than 50% in the first 100 hours.
It's a basking lamp with an extremely small footprint, very bad for growing cannabis.

This thread is not about the best UV-B lamp, it’s about how to mitigate UV-B damage. And my point was that most UV-B lamps used by most people have sufficient UV-A, and I used MegaRay as an example of UV-A from a UV-B lamp.

So what you think about that lamp in terms of use for Cannabis is not relevant, and even if it was, that lamp is fine (though not at all ideal) for use with plants (those lamps must be used correctly for plants).

Most UV-B lamps emit more UV-A than UV-B (other than specialty narrow-band medical grade lumiaires or LEDs).

So you will be using narrowband UVB?

No, not necessarily. For the experiments we have planned we will, of course, as well as other spectral ranges.

For our light source in our new Cannabis scientific research plant growth room we’re building this month (6’x8’ canopy) we’re using Philips MasterColor (942) CMH 315W lamps. They have good amount of UV-B and UV-A and we use them in (12) Greenbeams reflectors so there’s no heat shield and amazing irradiance uniformity. Once we’re done with our spreadsheet we’ll use that to calculate the UV-Bbe and UV-Abe from the lamp, as well as UV-B/UV-A ratio, and other ratios like UV-B/PPFD, etc.

 

[Bubbleblower]

I disagree completely. I and others (including you) wrote that UV-A (and PAR) is used by plants to mitigate UV-B damage.

Actually what you wrote was this:

“If you're using white light for PAR range irradiance then your plants are probally fine.”

“UV-A may have UV-B damage mitigating effects”​

​

In post 17 you corrected that a bit by hiding “peak effectiveness tens to occur at longer UV-A wavelengths (375-400 nm)” in one of your quotes -that most people will not have read- without making it clear you were wrong before.​

The math is simple, just look at a SPD of the sun near solar noon and it's easy to calculate..

Please show the math or cite the article you spoke about.

 

[Beta Test Team]

Honestly, it seems like in your posts to me you're trying to be "right," like you're trying to score points or something, as if you’re trying to prove what I’m writing is wrong to make your points look more correct. That’s why I’m less than enthused when I post to you.

It's like you see it as an "us" vs. "you" type of thing. And it's not. All that matters is science and being able to backup claims made. If you’re wrong (and you have been) that's not a bad thing, just like it's not bad when I'm wrong (as happens often! ).

Actually what you wrote was this:

“If you're using white light for PAR range irradiance then your plants are probally fine.”

“UV-A may have UV-B damage mitigating effects”​

​

In post 17 you corrected that a bit by hiding “peak effectiveness tens to occur at longer UV-A wavelengths (375-400 nm)” in one of your quotes -that most people will not have read- without making it clear you were wrong before.​

Thank you for proving my point so succinctly (see my quote).

And I was not wrong in what you're claiming (check the definition of "white light"). White light is all visible light, which includes UV-A from around 380 to 390 nm (according to CIE). PAR is 400-700 nm, and UV-A is 315-400 nm.

The math is simple, just look at a SPD of the sun near solar noon and it's easy to calculate..

Please show the math or cite the article you spoke about.

Please feel free to source these data yourself. That's the great thing about science, you can find the same data we found, and review it just like we have.

It's safe to assume I won't be providing you any answers or assistance from this point forward.



​

 

[Beta Test Team]

Shaggy here are a few other good studies you should read. Even if you don't understand all the terms, etc., you will gain from reading them.

Basically, after reviewing lots of studies our small meta-analysis found the following things can be done to limit possible negative effects of UV-B (such as growth inhibition, reduction in photosynethic rate, and leaf yellowing). This list is not exhaustive, nor completed:

- UV-B should be provided for the entire plant growth life (this has been well known for a long time). Applying high dosage UV-B irradiance randomly is not the way to go.

- With sufficient PPFD (especially in the blue spectrum), as well as UV-A is also beneficial, UV-B won't reduce photosynethic rate. Which can otherwise happen by affecting Rubisco, for example, or by reducing CO2 uptake by leaves.

- Don't over apply UV-B (as UV-Bba, aka UV-Bbe) as instantaneous or daily sum, regardless of the UV-A and PAR irradiance. Studies on Cannabis found even low dosage of UV-B increased THC vs. not supplementing with UV-B (as per day UV-Bba photon flux density). So until there more data on this, less is more we think.


Influence of PAR and UV-A in Determining Plant Sensitivity and Photomorphogenic Responses to UV-B Radiation
http://onlinelibrary.wiley.com/doi/10.1111/j.1751-1097.2004.tb00013.x/pdf


These last two are found in the book I posted the link to, here:
https://www.icmag.com/ic/showpost.php?p=6585669&postcount=18

Potential Effects of UV-B on Photosynthesis and Photosynthetic Productivity of Higher Plants

Non-damaging and Positive Effects of UV Radiation on Higher Plants

 

[Bubbleblower]

Thank you for proving my point so succinctly (see my quote).​

Not really, you said: “UV-A may have UV-B damage mitigating effects”​

The word “may” implies it is not certain, it may or it may not.​

White light is all visible light, which includes UV-A from around 380 to 390 nm (according to CIE).​

Who cares what it is according to the CIE, nobody on this forum -not even you- uses that definition, nor do the led suppliers that sell us these white leds. It only complicates things even more if UVA and white light are overlapping.​

It's safe to assume I won't be providing you any answers or assistance from this point forward.​

But I only asked how you arrived at your conclusion and to show evidence of your claims.​

If you can't you will not get these donations.​

 

[Beta Test Team]

Shaggy, in case you didn't see this in the other thread (https://www.icmag.com/ic/showpost.php?p=6727933&postcount=11), check this out (and click that link, too):

 

[shaggyballs]

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[shaggyballs]

Good info to talk about, thread has been dead for 6 years.