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Old 09-17-2014, 07:52 PM #1
shaggyballs
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Lighting requirement of the cannabis plant.

Every plant has different lighting needs.
Cannabis is no different.
But What are they?
Blue for veg and red for flower, is there more to it than this?

I thinks so, I just don't know what the requirements are.
Any help for the feeble minded???
Things such as:
Spectrums (far red ect.)
Par/Pur(intensity)
Morning , noon , evening differences if any.
This whole thing seems really complex.
HELP!
shag
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Old 09-17-2014, 09:01 PM #2
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Blue is not for veg and red is not for flowering - that's flawed logic based upon misunderstandings about sunlight (I know it's not your logic). Cannabis doesn't use light (in terms of spectral quality) much different than other higher C3 plants.

Please see our thread for a little info on this topic, you'll see the first ever (that we know of) Cannabis absorptance spectra (which shows absorbed photons by nm), and be able to calculate your own, too, with our software (spreadsheet).

You may want to download our absorptance spreadsheet and read the text, there's info in there that would likely help you with your questions (for example, wavelength ranges that are more uniquely used by Cannabis than other plants).

"Cannabis absorptance spectra: calculated and compared"
https://www.icmag.com/ic/showthread.php?p=6552578
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Old 09-17-2014, 09:12 PM #3
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WOW..This I just gotta see....Thanks.....Time to study!!!

shag

Thanks again
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Old 09-17-2014, 09:47 PM #4
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You're welcome. Feel free to ask questions in that thread if something isn't clear.

That thread is about light usage by typical higher C3 plants and cannabis, not intensity such as PAR (which is simply defined as PPF (photosynthetic photon flux), which is photon flux (micromole per square meter per second), from 400 to 700 nm).

Soon we'll release software (spreadsheet) that is used for lamp, LED, and system spectral quality and efficiency calculations, as well as intensity (at canopy) calculations and interconversions, with interactive suggestions for Cannabis based upon published research. All for free, because the more people working on this the more data we all have.
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Old 09-17-2014, 11:01 PM #5
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Well that got over my head quickly, looks like some quality info.
I will look at it again when my hair quits smokin'....LOL
shag
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Old 09-20-2014, 10:37 PM #6
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So we know what spectra cannabis absorbs... but can we correlate certain bands with specific biological processes?
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Old 09-21-2014, 02:33 AM #7
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Quote:
Originally Posted by shaggyballs View Post
Well that got over my head quickly, looks like some quality info.
I will look at it again when my hair quits smokin'....LOL
shag
I'd bet it is all very accurate, informative and thank you for posting it but I don't get it either.. there are things I have a hard time wrapping my brain around. I get red/blue/green and betting i'm doing it wrong, lol. i'll subscribe maybe I can learn. til I do, i'll keep buying the 1k HPS cheapie I guess. is there a short/simple explanation of all that? red and blue? lol.
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Old 09-21-2014, 02:37 AM #8
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Yes, for the most part. Cannabis is not much different than other C3 plants. It will use wavebands (like UV-b, PAR, far-red) like other plants, and although there are differences they're not not large.

In terms of photosynthesis, it's PAR range light quantity (amount, as photons per second and day) that matters much more than light quality (red, blue and green amounts).

The McCree curve (plant action spectrum as quantum yield) is not really all that important for various reasons, but a main one is McCree used 150 PPF for irradiance, which is very low, and under high irradiance (like Cannabis is grown with) the quantum yield is not well represented by the McCree curve. Also, McCree used narrow wavebands, so his curve doesn't show the "Emerson effect" from white light vs. near monocrhomatic light.

Light quality is important for photomorphogenesis reactions, like open/closing stomata, phototropism, etc. And for these issues we can look to other similar C3 plants to have a good idea how Cannabis responds.
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Old 09-21-2014, 02:58 AM #9
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Quote:
Originally Posted by Snook View Post
I'd bet it is all very accurate, informative and thank you for posting it but I don't get it either.. there are things I have a hard time wrapping my brain around. I get red/blue/green and betting i'm doing it wrong, lol. i'll subscribe maybe I can learn. til I do, i'll keep buying the 1k HPS cheapie I guess. is there a short/simple explanation of all that? red and blue? lol.
Yup

See what I wrote above, about why in terms of photosynthesis, red, blue and green don't really matter that much. It's the PAR range (most active light for photosynthesis) irradiance (amount of light striking leaves) as photons (particles of light) that matter the most.

For Cannabis, somewhere in the range of 600 to 1,000 PAR (as PPFD, the amount of PAR photons in a meter squared) is a good goal indoor or greenhouse. Above 1,000 PPFD for more than a few hours is not a good idea, generally, unless the environment is very well controlled.

So your HPS is good in terms of photosynthesis, in fact, it's YPF/PPF ratio is very high (which means per total light output there's more photons that are more effective at driving photosynthesis than for example, an MH).

However, your el' cheapo HPS lacks important wavebands for some photomorphogenesis. For example, it's likely there is more yellow light from your HPS than is good for the plants, as well as more far-red light than is helpful (leads to plant stretch). Around 10% blue light (as total radiant PPF) is a good minimum goal for plant growth lighting.

I hope clears things up a little, if not, let me know and I'll try to help.
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Old 09-21-2014, 03:54 AM #10
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UV-b is an waveband range we're interested in for Cannabis, specifically. Like other plants, Cannabis produces secondary metabolites (which include cannabinoids). And UV-b irradiance can increase THC production in Cannabis.

Every indoor and most greenhouse grown plants don't get enough UV irradiation as compared to sunlight.

The spreadsheet we're working on, to analyze spectral quality of light sources, includes UV-b and UV-a features, including plant action spectrum (how plants use UV-b and UV-a light for photosynthesis).

With our spreadsheet a grower can input the data from the SPD of their UV-b lamp, or CMH HID lamp, etc., and learn how well it may function for Cannabis in terms of photosynthesis, but also in terms of THC production.

It has been found between (and likely less than) 6 to 14 kJ m-2 UV-Bbe per day (that just means biologically effective, the same thing as action spectrum) can increase THC on flowers by over 20% and leaves by over 30%. Now, we don't expect those numbers to be happens all the time UV-b is applied, but it's a good indicator. And there is other published research with similar findings.

What's cool about our spreadsheet is a grower can use a rather inexpensive UV meter ($200) to find out the UV-Bbe irradiance their plants are getting while they're growing. Rather than an expensive UV-B meter that's well over $2,500. And with that info our spreadsheet will tell the grower many kilo-joule of UV-Bbe that is per day, and if it's sufficient to boost THC production as found in various published research.

A little off-topic, a grower can also use a rather inexpensive lux meter (around $150 to $200) and our spreadsheet to find the PPFD their plants are getting, and the DLI (PPFD per day). That way a grower can know if they're giving their Cannabis plants too little, enough, or too much light. Rather than spending around $1,000 on a good quantum sensor.
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