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

[shaggyballs]

The spectrum of photosynthetically active radiation (PAR) may
be important to reduce the destructive effects of
UV radiation.
https://www.icmag.com/ic/attachment.php?attachmentid=285655&d=1411766025

This is beyond my thinking.
Is this saying the color of the light has an effect on UV radiation?


Shag

 

[magiccannabus]

If I understand it correctly, the plant seems to adjust its chloroplasts and other photo reactive compounds to suit the spectrum its getting, and that some mixes of these compounds provide more protection against UV damage than others. There's just a huge amount of info in such a short document though, and I am sure some others here understand this better than I do.

 

[shaggyballs]

Shag

 

[magiccannabus]

lol poor lil guy is drowning!

 

[Beta Test Team]

The spectrum of photosynthetically active radiation (PAR) may
be important to reduce the destructive effects of
UV radiation.
https://www.icmag.com/ic/attachment.php?attachmentid=285655&d=1411766025

This is beyond my thinking.
Is this saying the color of the light has an effect on UV radiation?


Shag

You're over thinking it. That's the report I uploaded, correct?

Here's the short version: If you're using white light for PAR range irradiance then your plants are probally fine (unless you're applying too much UV-B). Provide at least 200 or 300 PPFD and you're probally in the clear.

See this post of mine to HUGE; note the bolded studies:
https://www.icmag.com/ic/showpost.php?p=6572403&postcount=104

What is the appropriate amount of UV?
Is there a level or a ratio that is optimum?

There is no proven ideal amount of UV-B as photon flux (umol/m-2/s-1 from 280-320 nm) or DLI, and the same goes for UV-A. This is an area we plan to study in 2015, as well. If you haven’t read my comments in Shaggy’s thread about UV-B you may like to:
https://www.icmag.com/ic/showthread.php?t=293184

Somewhere in the ballpark of 1 to 15 kJ/m-2/day-1 UV-B is the target range. The best study on this topic thus far used the older UV-B action spectrum of higher plants by Flint, and found around 6, 8, and 14 kJ/m-2/day-1 all proved very effective at increasing THC.

UV-B increases not only THC, but also some secondary metabolites like some terpenes and flavonoids.

Potential UV-B DNA and cellular damage is mitigate by strong PAR irradiance (as PPFD, at least 10% of the sun's peak PPFD of about 2,000). For example:

Effects of prolonged UV-B exposure in plants
http://www.ubrisa.ub.bw/bitstream/handle/10311/491/Effects of prolonged.pdf?sequence=1

Effects of Ultraviolet-B Radiation on Photobiology
http://www.vitamindwiki.com/tiki-download_wiki_attachment.php?attId=534

To mitigate possible DNA and cellular damage from UV-B ensure you're providing strong white light. So, as PAR (which is technically defined as PPFD), you would want at least 10% of the sun's peak PPFD in your garden to prevent UV-B damage (as much as possible). And the peak sun PPFD is around 2,000, it's higher at some locations but 2,000 PPFD is a good rule.

Therefore, provide at least 200 PPFD to your plants while irradiating them with UV-B. And because 200 PPFD is a low light level, your plants are probably safe as is.

Granted, this all depends upon the amount of UV-B you're providing throughout the day and per second.

Also, UV-A may have UV-B damage mitigating effects, too.

 

[Beta Test Team]

lol poor lil guy is drowning!

At least he'll be protected from UV-B underwater!

 

[shaggyballs]

-

 

[Beta Test Team]

You're welcome.

These topics are pretty dense, and you're juggling at least 4 I can see (from your threads), so I can understand how you feel. Maybe take one or two a time?

Like a skyscraper, build a solid foundation and you can reach the stars

That joke about water and UV-B wasn't about you, it was about that little guy bobbing in the water. Hope I didn't offend.

 

[shaggyballs]

-

 

[Ranger]

The spectrum of photosynthetically active radiation (PAR) may
be important to reduce the destructive effects of
UV radiation.
https://www.icmag.com/ic/attachment.php?attachmentid=285655&d=1411766025

This is beyond my thinking.
Is this saying the color of the light has an effect on UV radiation?


Shag

what i gathered was that science doesn't yet know of the relationship between different absorptions of differing wavelengths on plant physiology. and something about LED lighting being a possible solution to indoor horticultural needs.

they base this on a need for indoor farming due to in part the harsh outdoor conditions from global warming.

sounds like it was paid in part by LED industry and also the global warming advocacy. sounds about right.

 

[Bubbleblower]

Is this saying the color of the light has an effect on UV radiation?

the appropriate amount of UVB is only appropriate if we balance the rest of the spectrum.

It is especially important to have enough UVA in the spectrum and the amount of UVB needs to be build up slowly.

That's the report I uploaded, correct?

Here's the short version:

If the photosynthetic performance of different light sources is to be compared, then the presently used metrics based on the quantum system are erroneous, not coherent and therefore fail.

 

[Bubbleblower]

It is especially important to have enough UVA in the spectrum <edit> in case you want to use UVB </edit>

 

[shaggyballs]

-

-

 

[Beta Test Team]

If the photosynthetic performance of different light sources is to be compared, then the presently used metrics based on the quantum system are erroneous, not coherent and therefore fail.

You keep claiming this but have yet to provide a valid scientific reason why. Like I wrote to you a few times already, it's the most active QY wavelength ranges that are used for PAR (so, 400 to 700 nm), not all wavelengths ranges that are used for photosynthesis, because for that matter we also would have to include all of UV-B, etc.

Making a factual claim without citing actual facts is what we think is a fail

I won't bother you again about this issue.

 

[Beta Test Team]

Thanks for the reply Bubbleblower
So what i think your saying is :

If you plan on using UVB you better have the right amount of UVA.
Is this correct?

Sounds like it might be a ratio thing????

Treading water a bit now, for how long????

shag

PAR is more important than UV-A to mitigate possible UV-B damage, at least as thus far proven by science. And any lamp that provides sufficient UV-B will generally also provide sufficient UV-A, unless possibly some LEDs, or of course using filters for the light source.

 

[Bubbleblower]

If you plan on using UVB you better have the right amount of UVA. Is this correct?

Sounds like it might be a ratio thing????

Exactly that. If you add UVB you have to change everything else in the right proportion.

PAR is more important than UV-A to mitigate possible UV-B damage, at least as thus far proven by science.

Pffffft, we start out with PAR, while we don't have UVA yet. How about you give us all the correct ratio's how UVB should be added?

You keep claiming this but have yet to provide a valid scientific reason why.

Not claiming, but quoting from “Horticultural lighting – present and future challenges” page 434 chapter 6.
You put it up, so I assume you read it.

[FONT=Times New Roman, sans-serif]Now let's stay on topic, could you post some studies that prove UVB increases THC (no Lydon)? [/FONT]

 

[Beta Test Team]

The spectrum of photosynthetically active radiation (PAR) may
be important to reduce the destructive effects of
UV radiation.
https://www.icmag.com/ic/attachment.php?attachmentid=285655&d=1411766025

This is beyond my thinking.
Is this saying the color of the light has an effect on UV radiation?


Shag

We came across good information about this topic while researching the UV-B and UV-A action spectrum by Flint & Caldwell ('relative quantum response') of higher plants (as used by Lydon, and other research on Cannabis).

This states blue range PAR irradiance, and longer wavelength UV-A irradiance, are more effective in terms of mitigating UV-B damage than longer wavelengths like yellow and red ranges (generally):

Mitigation of UV-B response by visible (especially blue light) and UV-A flux is best documented in photoreactivation (PR) of damage to DNA since this radiation drives the photolyase enzyme. For higher plants, peak effectiveness tens to occur at longer UV-A wavelengths (375-400 nm) [12,13]. In experiments with light-grown higher plants, both supplemental UV-A and blue light can aid in ameliorating UV-B caused chlorosis [14]; this may or may not involve PR.

…

...

...

[Note: "chlorosis" is basically the yellowing of the leaves due to lack of cholorphyll.]

From:

Use and Evaluation of Biological Spectral UV Weighting Functions for the Ozone Reduction Issue
(Flint & Caldwell, 2006)

To read more about this specific topic see the book link I posted in the next post (below this one).

The same rule I suggested still applies for PAR irradiance, at least 200 or 300 PPFD. 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 - so if UV-Bbe (weighetd UV-B) is 5 PFD, UV-Abe should be greater than 25 PFD.

There are other great chapters in that book, like:

Quantification of biological effectiveness of UV radiation

 

[Beta Test Team]

I just happen to find a free full version of that book I cited above (it's about $100) on ResearchGate, for those that want to read more about this topic (and plant use of UV-B in general).

The book was uploaded by an author of a study (see below) within the book, otherwise it would not have been allowed to be uploaded to ResearchGate:

Environmental UV Radiation: Impact on Ecosystems and Human Health and Predictive Models
http://www.researchgate.net/profile...olecular_Level/links/0deec52bea22db4ded000000

Here's another interesting study within that book I'm reviewing now, citing low PPFD (e.g. <900) as important, not high PPFD (e.g. >900):

UV-B and UV-A Radiation Effects on Photosynthesis at the Molecular Level

ABSTRACT

Ultraviolet radiation is a well known damaging factor of plant photosynthesis. Here we studied the mechanism of damage induced by the UV-B and UV-A spectral regions to the light energy converting Photosystem II (PSII) complex, which is the origin of electron flow for the whole photosynthetic process. Our results show that the primary UV damage occurs at the catalytic Mn cluster of water oxidation, which is most likely sensitized by the UV absorption of Mn(III) and Mn(IV) ions ligated by organic residues. The presence of visible light enhances the photodamage of PSII, but has no synergistic interaction with UV radiation.

UV-induced damage of PSII can be repaired via de novo synthesis of the D1 and D2 reaction center protein subunits. This process is facilitated by low intensity visible light, which thereby can protect against UV-induced damage. However, the photodamage induced by visible light at high intensity (above 1000 µEm−2s−1) cancels the protective effect. The protein repair of PSII is also retarded by the lack of DNA repair as shown in a photolyase deficient cyanobacterial mutant.

 

[Bubbleblower]

Now I should get to 50 posts easily

The plant's ability to cope with the damaging effects of UV radiation depends on its ability to reduce exposure (through optimization of growth and production of UV-absorbing compounds) and its ability to repair or replace damaged molecules. The protective effects of high PAR against elevated UV-B may also be indirect, by increasing leaf thickness and the concentration of flavonoids and other phenolic compounds known to be important in UV screening. The expression of these mechanisms of UV resistance is greatly influenced by spectral quality and irradiance. Action spectra indicate that wavelengths in the UV-A to blue range are most effective in repairing DNA damage. To achieve meaningful results in UV-enhancement studies, it is therefore important that a proper spectral balance be maintained in the ratio of PAR-UV-B and UV-B-UV-A radiation and that an improved BSWF be used to give greater weight to the UV-A component. Further studies are required to delineate the nature of specific interactions of UV-A, UV-B and PAR effects in selected plants. Efforts should be made to carefully control, monitor and report each of these wavebands when conducting UV studies.

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)?

 

[Beta Test Team]

Now I should get to 50 posts easily

The plant's ability to cope with the damaging effects of UV radiation depends on its ability to reduce exposure (through optimization of growth and production of UV-absorbing compounds) and its ability to repair or replace damaged molecules. The protective effects of high PAR against elevated UV-B may also be indirect, by increasing leaf thickness and the concentration of flavonoids and other phenolic compounds known to be important in UV screening. The expression of these mechanisms of UV resistance is greatly influenced by spectral quality and irradiance. Action spectra indicate that wavelengths in the UV-A to blue range are most effective in repairing DNA damage. To achieve meaningful results in UV-enhancement studies, it is therefore important that a proper spectral balance be maintained in the ratio of PAR-UV-B and UV-B-UV-A radiation and that an improved BSWF be used to give greater weight to the UV-A component. Further studies are required to delineate the nature of specific interactions of UV-A, UV-B and PAR effects in selected plants. Efforts should be made to carefully control, monitor and report each of these wavebands when conducting UV studies.

I don't know why you couldn't reach 50 posts before now, but regardless, I'm glad to help you reach your goal.

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. The only difference is I posted the science to explain why and how, with updated evidence regarding the most effective wavelength ranges (that were already mentioned by all of us in this thread).

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.

The basic idea is to approximate the spectral characteristics of the sun (near solar noon) with respect to UV-B and UV-A ratios and as percent of PPFD.

There is no hard ratio of UV-B to UV-A or UV-B to PPFD, or UV-B to UV-A to PPFD. Ballpark is about the best we have right now. So a general rule of 10 times the amount (irradiance) of UV-A to UV-B, ideally as weighted UV-A and UV-B, can be found in the published literature.

We have reviwed well over a few dozen studies on UV-B, UV-A and PAR, with respect to UV-B. That's where these data I'm writing about come from.

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:

MINIMUM distance setting of 12" will produce approximately 150-200 microwatts per square centimeter (uW/cm2) of UVB and 900-1200uW/cm2 of UVA.

P.S.
You'll probably like this, it's about ratios of UV-B to UV-A and PAR range in electrical light and filtered sunlight light vs. sunlight and the possible impacts on plant science research. We're going to replicate this work for our upcoming experiments with UV-B and Cannabis to compare vs. using a lab grade UV-B lamps setup:

A new filter that accurately mimics the solar UV-B spectrum using standard UV lamps: the photochemical properties, stabilization and use of the urate anion liquid filter
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3040.2010.02240.x/abstract

.