are the mars hydro adlights worth it UV, IR, RED

[Delps8]

Found this while reading some other Frontiers papers.

 

[Rocket Soul]

Blue light inhibits cells expansion, red light tends to increase cell expansion. One of the reasons to use a veg light is that it makes plants short and compact. I use a veg LED and a flower LED. The plant below was vegged for about 40 days under a Growcraft X3 light. It was topped at day 21 and LST'd and was then grown under their flower light.

View attachment 5420993

View attachment 5420995

The only % "requirement" that I've been able to find is a comment by Bugbee that flower lights should have at least 4% blue to avoid misshapen plants.

Bugbee's latest (as of this Spring) advice was to use a white LED with some far red. He referred to the far red as being like a "flamethrower" for growth. This spectrum is from one of his recent videos:

View attachment 5420987

Bugbee's advice is that while spectrum is key to shaping plants, the most important issue is to maximize light levels. Mitch Westmoreland, a PhD student under Bugbee, validated that in the videos he released this spring in which he shared portions of the research he did for this thesis. In the videos, Westmoreland states that they were not able to find benefit from using UV light but acknowledges that there are a huge number of combinations of exposure time, different wavelengths, and different intensities so it's quite possible that UV light has a benefit. His issue is that they are unable to demonstrate any benefit.

If a grower has found an approach to using UV that is reproducible, I would highly recommend that the grower contact Mitch and share that information. He's just one person working in a lab so he's limited in what he can test. On the other hand, if someone finds a winning combination, everyone would benefit if it could be reproduced.

PAR, short for "photosynthetically active radiation, covers the 400 to 700nm range. That's been the historical definition but Bugbee has adovocated that ANSI introduce ePAR or "extended PAR" which would extend the upper limit from 700 to 750. The lower limit is not changed because light with a wavelength shorter than 400nm is not photosynthetically active, per above.

That's not to say UV doesn't impact how plants grow. The "not photosynthetically active" means that it doesn't play a role in photosynthesis.

The screenshot below is from this page:
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The graphic below shows the percentage make up of various grow lights and it confirms that HPS, historically used as a flower light, does have 4% blue in the spectrum.

View attachment 5420989

Very nice post

One thing i wondered about their research into blue light response is if they can reliably say whether its the blue light amount or the height of the blue spike that is responsible for effects. Do the effects come down to the % amount or the intensity of the dominant blue peak. Do you know if they have some measure or method for this?

 

[amneziaHaze]

UV C is very good for that, no argument.

Fortunately, the atmosphere filters out 100% of UVC because it's harmful to living beings, even in very small doses.

I did it last grow still got mold but only the buds that where crowded

 

[Delps8]

I did it last grow still got mold but only the buds that where crowded

Ouch. Sorry to hear that.

 

[Delps8]

Very nice post

Thank you.

One thing i wondered about their research into blue light response is if they can reliably say whether it's the blue light amount or the height of the blue spike that is responsible for effects. Do the effects come down to the % amount or the intensity of the dominant blue peak. Do you know if they have some measure or method for this?

I haven't seen anything that looks at it from the perspective but my sense is that it's the percentage and it's a function of long term exposure. I say that only because blue light inhibits cell expansion, which leads to shorter plants and smaller leaves. (I think that the issue of smaller leaves is in the paper?)

The characteristic of having smaller leaves is a morphology/long term/chronic issue vs an acute issue so my History-major brain sees a correlation between the diminished leaf size and leaf surface area and a reduced yield, but I can't say that it is, in itself, the causal factor.

 

[Rocket Soul]

Thank you.


I haven't seen anything that looks at it from the perspective but my sense is that it's the percentage and it's a function of long term exposure. I say that only because blue light inhibits cell expansion, which leads to shorter plants and smaller leaves. (I think that the issue of smaller leaves is in the paper?)

The characteristic of having smaller leaves is a morphology/long term/chronic issue vs an acute issue so my History-major brain sees a correlation between the diminished leaf size and leaf surface area and a reduced yield, but I can't say that it is, in itself, the causal factor.

To me it seems hard to believe its a straight percentual influence; if the plant really senses the absolute percentages then what are all those actionspectrums with peaks and valleys for? I mean it seems like the plant definitely likes some parts of the spectrum better than others.

This study shows that at least on the red side the plant does care about composition of red boost, 640+660>660, and this being especially obvious in higher light intensity.

Frontiers | The role of red and white light in optimizing growth and accumulation of plant specialized metabolites at two light intensities in medical cannabis (Cannabis sativa L.)

The cultivation of medical cannabis (Cannabis sativa L.) is expanding in controlled environments, driven by evolving governmental regulations for healthcare ...

www.frontiersin.org

And ill see if i can dig up the paper from icmag: it had some quite nice yield results for uv supplement: no yield loss even yield gain for some uv conditions.

Im thinking that the peaks of the spectrum would define which genes are more "switched on" in the plant. But there is probably a percentual correlation to blue% even though this may not be the causally driving factor

Edit:

Frontiers | Indoor grown cannabis yield increased proportionally with light intensity, but ultraviolet radiation did not affect yield or cannabinoid content

Cannabis (Cannabis sativa) flourishes under high light intensities (LI); making it an expensive commodity to grow in controlled environments, despite its hig...

www.frontiersin.org

It has some nice points re uv supplement, no yield loss, possible yield gain even when adding uva/uvb which is a bit counterintuitive: adding 3.1 something of ppfd in the uva/uvb range made a 600ppfd cannopy yield similar to a 800ppfd cannopy with no uv.

 

[Delps8]

To me it seems hard to believe its a straight percentual influence; if the plant really senses the absolute percentages then what are all those actionspectrums with peaks and valleys for? I mean it seems like the plant definitely likes some parts of the spectrum better than others.

This study shows that at least on the red side the plant does care about composition of red boost, 640+660>660, and this being especially obvious in higher light intensity.

Frontiers | The role of red and white light in optimizing growth and accumulation of plant specialized metabolites at two light intensities in medical cannabis (Cannabis sativa L.)

The cultivation of medical cannabis (Cannabis sativa L.) is expanding in controlled environments, driven by evolving governmental regulations for healthcare ...

www.frontiersin.org

And ill see if i can dig up the paper from icmag: it had some quite nice yield results for uv supplement: no yield loss even yield gain for some uv conditions.

Im thinking that the peaks of the spectrum would define which genes are more "switched on" in the plant. But there is probably a percentual correlation to blue% even though this may not be the causally driving factor

Edit:

Frontiers | Indoor grown cannabis yield increased proportionally with light intensity, but ultraviolet radiation did not affect yield or cannabinoid content

Cannabis (Cannabis sativa) flourishes under high light intensities (LI); making it an expensive commodity to grow in controlled environments, despite its hig...

www.frontiersin.org

It has some nice points re uv supplement, no yield loss, possible yield gain even when adding uva/uvb which is a bit counterintuitive: adding 3.1 something of ppfd in the uva/uvb range made a 600ppfd cannopy yield similar to a 800ppfd cannopy with no uv.

Thank you for providing these papers. Both very interesting reads.

The latter - I agree with your comment on that finding and it would be interesting to see the outcome of combination UV treatments with the 800µmol and 1kµmol levels. "interesting" is key because the cost of adding supplemental lighting vs increasing the PPFD of the PAR light is very high. Coupled with that is the unambiguous increase in yield that comes with a higher PPFD in the PAR range. Thus "interesting" but, unless there's a signficant increase in yield or quality, it's just not worth it at the commercial level. For the personal producer/home grower, I think it's fair to say that novelty has significant value so sales of supplemental lighting will continue to reflect marketing effort for some time.

Re 640+660 > yield than 660 — 660 is the standard wavelength for most lights but, if the cost of adding in 640nm LED's isn't signficant, then I would think that we'll see them being introduced in the next generation of LED designs. I have no idea of the cost of 730 vs 640 but 730 is starting to be used in commodity lights - HLG and Growlight Australia come to mind but I'm sure there are others.

Back to the present issue - the second paper provides insight into the complexity of this type of work in that the wavelengths of the UV bands are dissected precisely and the exposure duration, intensity, and timing are al factors. Perhaps there is a combination of those factors that provides a significant benefit but until then, "more research is needed".