Can a light get too efficient

[GrowLightResearch]

after a leaf strip it seems to get a little cooler but I'm not measuring heat at very many points. I will pay closer attention to temps next time I defoliate.

Fascinating. I really do not want to open another can of worms. I have heard someone say they defoliate because the bottom leaves waste energy. Why do you defoliate? Is it energy related? To the point where it could change room temperature? Just curious.

 

[Schalalala]

Very little is absorbed between deep blue and deep red.[...] Very little green yellow orange is absorbed.

No no no... you need to get a refresh/ dig a little deeper when it comes to absorption.
Cannabis specific absorption spectrum:
https://www.icmag.com/ic/showthread.php?t=293045
Check out the other things this group posted. Well worth a read.

 

[Ryante55]

Fascinating. I really do not want to open another can of worms. I have heard someone say they defoliate because the bottom leaves waste energy. Why do you defoliate? Is it energy related? To the point where it could change room temperature? Just curious.

More to let light in to the lower canopy and increase airflow humidity can go down alot too so you can cut down on how much the dehumidifier runs. Imo it helps prevent pests and mold.

 

[Yodaweed]

Very spectra dependent. The maximum oxygen evolution utilization, at 680nm is 27%. Very little is absorbed between deep blue and deep red. The majority stored, is stored as glucose, which does not amount to much except in sugar cane. A good percentage of blue is dissipated as heat because it has 50% more energy than red. Very little green yellow orange is absorbed.


Fluorescence, the photons re-emitted at a higher wavelength, does lose a little energy in the wavelength conversion. Hopefully that photon is used by a leaf lower in the canopy. Fluorescence only happens in red spectrum.

You are correct with the spectrum typically used. A very small percentage is utilized.




Plants use photons mostly in photochemical oxidation of water, and to reduce carbon dioxide to organic carbon compounds, typically sugars.
The biochemical production of secondary metabolites (e.g. cannabinoids) by these carbon reactions is where things get interesting.

Mostly off topic. Except maybe how the efficiency of photosynthesis is affected by photorespiration in the biochemical carbon reduction. I do not understand chemistry well enough to understand biochemical processes.

NEED TO COOL MEH GROW RUM THROW MORE PLANTS IN!

 

[GrowLightResearch]

No no no... you need to get a refresh/ dig a little deeper when it comes to absorption.

Are you thinking that the cannabis absorptance plots are showing the same as the McCree Absorbance and Action spectrum plots?
Like this:


Notice how the plots you referred to look nothing like the above Absorbance and Action spectrum plots?


In photobiology absorptance shows of the absorbed spectrum that the energy level of the photon (blue has 50% more energy than red) only the number of photons matter and not their energy level.

Notice absorptance vs. absorbance. Those IC plots are actually absorptance not absorbance. Absorptance is the fraction of the absorbance that has an effect on plant photobiology or quantum yield of photosynthesis.
Quantum yield of photosynthesis (Φ) is:

Number of photochemical products ÷ Total number of quanta absorbed​

The data was taken from a study of cannabis reflectance and transmittance for aerial detection of illegal cannabis.

Spectral Discrimination of Cannabis sativa L. Leaves and Canopies, Daughtry and Walthall​

​

 

[Schalalala]

Notice how the plots you referred to look nothing like the above Absorbance and Action spectrum plots?

Yes, that is basically my point. You said that mainly blue and deep red get absorped and I think that is wrong.
As the IC graph shows, nearly every wavelength gets absorped to a high degree. Weight the action spectrum with the absorption spectrum, then you know how useful a specific photon really is.
If Cannabis had a absorption spectrum like the one you posted, white LEDs would loose big time against a 450/660nm combination.

Those IC plots are actually absorptance not absorbance. Absorptance is the fraction of the absorbance that has an effect on plant photobiology or quantum yield of photosynthesis.

So where do you get that from?? They clearly name the y-axis "absorped photons by nm" not "Relative Effect of absorpted photons on photosynthesis".

 

[GrowLightResearch]

So where do you get that from??

Relative means action relative to absorbance. Absorptance shows the relative difference between absorbance and action.

It's also in the thread. This was a few posts down from the link you gave.

white LEDs would loose big time against a 450/660nm combination.

Yes they do as well as most all plants.

There is a huge bias against 450/660 BR. Many who used HPS tried the cheap RB fixtures advertised by charlatans as equivalent to an XXX watt HPS which is far from true. Many still think wall watts of a grow light has some significance when buying a light. It does not.

There's more to light than just photosynthesis. At the University of Florida they are mapping the photosynthesis carbon reactions. They expose the plants to various wavelength then analyze the plant's volatile compounds (e.g. terpenoids, phenylpropanoids, monoterpenoids) using gas chromatograph mass spectrometers.

But as far as photosynthesis goes much fewer photons in the 500-600nm are absorbed. Most photons are utilized to oxidize water (oxygen evolution) and reduce carbon dioxide to produce carbon molecules. The action plot I posted showed absorbance and action by measuring oxygen evolution.

The plot from IC was the difference between absorbance and action. But you need to understand that absorptance is measured using the photons that were absorbed so it is relative to the number of photons absorbed by the leaf, not the number of photons that reached the leaf.

 

[Schalalala]

Don't have much time today, therefore I cannot answer in depth. Please cite the source of your action/absorption spectrum as it does not come from Daughtry and Walthall or at least I cant find it there.
I think your spectrum doesn't show the absorptance of a whole leaf and this is/was where the red/blue hype/misconception starts/started. Maybe someone else can explain this to you quickly. For me, as a non-native speaker, this is just to time-comsuming right now.

Source: http://photobiology.info/Gorton.html
Ahh, and have you found the excel sheets from Beta Test Team?? I would highly appreciate a link/copy!

 

[burnpile]

So with that logic the more plants you have in a room the cooler it runs? More plants more heat absorbed...I don't think that's how it works

I do know that my room with no plants and lights on gets 10 / 20 degrees hotter than when there are 4 in there.

 

[Rocket Soul]

Room usually runs cooler with less plant mass like after a leaf strip it seems to get a little cooler but I'm not measuring heat at very many points. I will pay closer attention to temps next time I defoliate.

Same as in well documented grow by GML. Thermodynamics is easy to argue from a theoretical standpoint, but real life data is allways going to trump what works in theory.

Either the increased airmovement causes the heat generated to dissipate thru walls in your room. Or it might have to do with humidity/transpiration/evaporation but it seems counterintuitive as water evaporating will lower temps, and i would say there would be less after a leafstrip.
In any case thx for real life examples in this discussion, more is needed.

 

[Rocket Soul]

I do know that my room with no plants and lights on gets 10 / 20 degrees hotter than when there are 4 in there.

Was there a difference in humidity? Transpiration/evaporation from the plants should lower temprature of your room.

 

[burnpile]

Was there a difference in humidity? Transpiration/evaporation from the plants should lower temprature of your room.

Yes, humidity dropped into 20's / 30's, from the 50's.

 

[Rocket Soul]

Yes, humidity dropped into 20's / 30's, from the 50's.

Think of it like this: when youre heating your room youre heating the air and the water disolved in the air: higher humidity means it takes more energy to heat, just like with a bigger heatsink the temps rise less per heat energy put into it.

 

[GrowLightResearch]

So where do you get that from??

The action and absorption for oxygen evolution came from here.
http://6e.plantphys.net/topic07.01.html

Ahh, and have you found the excel sheets from Beta Test Team?

Spreadsheet: https://www.icmag.com/ic/showthread.php?t=293045


Here is additional info on chlorophyll absorption spectra
https://www.google.com/search?q=chlorophyll+Absorption+spectra&ie=utf-8&oe=utf-8

http://6e.plantphys.net/topic07.01.html

 

[wietefras]

Who cares about Chlorophyll absorption spectra? Since only a few percent of the light is actually used by the plant for creating biomass, this whole process is hardly significant anyway. Let alone that three is any need to look at the absorption spectra for only two of the many pigments present in plant leaves.

It's this whole stupidity of looking at Chlorophyll spectra that got us this blurple nonsense. Sure if you only look at Chlorophyll then blurple makes sense. Yet if you compare YPF (McCree) for a burple with 10% blue then it's 90% "efficient" on the RQE chart versus 85% for a 3000K 80 CRI fluorescent led. Hardly the 30% difference the blurple sales pitch was trying to make us believe (ie the "green is useless!" bs)

Spectrum is not relevant for how much the room heats up. It's even only marginally relevant for the efficiency of the plants.

 

[GrowLightResearch]

Who cares about Chlorophyll absorption spectra?

Possibly someone growing plants under LED lighting? Although the question is off topic.

stupidity.. nonsense

Thanks for the example of such.
Blurple? Is that what is says on you magenta crayon? Maybe you soon you will be ready for the big boy colors. It does have an infantile ring to it, so I guess it's okay for you. For the record most adults use magenta rather than blurple. Not that you care. Just trying to help you grow up.

Spectrum is not relevant for how much the room heats up

Old news, catch up please.

It's even only marginally relevant for the efficiency of the plants.

Not the topic here. But... do you even care?

Since only a few percent of the light is actually used by the plant for creating biomass

Why is that significant? Did someone mention biomass? Is that the topic?

this whole process is hardly significant anyway.

Okay I get it. You like to say things just say things don't you? Topic be damned.
Do you have anything on a more positive note to contribute? Feel free to join in after you grow up. For now go and enjoy Barney and your "burple".

 

[Olive Drab Green]

I am more worried about winter than summer honestly. The LED plants don't want to go under about 78 degrees. luckily it is cheaper to heat the room than cool it.

I’ve had my plants literally dealing with single digit and negative temperatures indoors for a few days last month. I did eventually get a heat pad, though.

 

[wietefras]

Not the topic here. But... do you even care?

Efficiency is not the topic here?

Why is that significant? Did someone mention biomass? Is that the topic?

You don't even remember why you brought up photosynthesis or that you pretended spectrum plays any role in this? Or was that just so you could show off your vast knowledge on how to use Google and the copy and paste key combinations?

The "veterans" here still remember (from only a few months ago actually) how much of a hard time you had understanding that it's not just Chlorophyll in plants. That you should look at McCree's charts instead. Few months later and you pretend to know all about the subject. Yet you still post that useless Chlorophyll chart anyway.

Just stop pretending. No one is buying it.

 

[Cold$moke]

I’ve had my plants literally dealing with single digit and negative temperatures indoors for a few days last month. I did eventually get a heat pad, though.

Howdid you do this?

I got my room down to abot 30 degrees once (long story)

My plants where toast with ice on my root balls
It was cool to see my nft like a frozen fountain lol

So how did you hit single digits and lower?

 

[Sour Wreck]

Howdid you do this?

I got my room down to abot 30 degrees once (long story)

My plants where toast with ice on my root balls
It was cool to see my nft like a frozen fountain lol

So how did you hit single digits and lower?

damn, you didn't take pics of the nft frozen fountain, did you?