Lighting requirement of the cannabis plant.

shaggyballs · Sep 17, 2014

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??? :biggrin:

Things such as:
Spectrums (far red ect.)
Par/Pur(intensity)
Morning , noon , evening differences if any.
This whole thing seems really complex.
HELP!

shag

Beta Test Team · Sep 17, 2014

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

shaggyballs · Sep 17, 2014

WOW..This I just gotta see....Thanks.....Time to study!!!
:smoke out:

shag

Thanks again

Beta Test Team · Sep 17, 2014

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.

shaggyballs · Sep 17, 2014

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

hyposomniac · Sep 20, 2014

So we know what spectra cannabis absorbs... but can we correlate certain bands with specific biological processes?

Snook · Sep 21, 2014

shaggyballs said:
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 :tiphat:

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. :tiphat:

Beta Test Team · Sep 21, 2014

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.

Beta Test Team · Sep 21, 2014

Snook said:
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.

Beta Test Team · Sep 21, 2014

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.

Beta Test Team · Sep 21, 2014

Neat.

We think we just stumbled upon a reason why UV-B irradiance may increase THC, and this seems to be the first time anyone has suggested this (including in all published research we have reviewed): jasmonic acid pathway

It's been found that jasmonte (probably as jasonic acid) increases THC in Cannabis*, and the following figure shows how UV-B irradiance effects jasmonate in the plants (which would mean affecting the jasmonic acid pathway):

(From "Plants and Microclimate: A Quantitative Approach to Environmental Plant Physiology" [3rd Ed.])

*http://www.sid.ir/FA/VEWSSID/J_pdf/5002713910205.pdf

We just may have to write up a research report about UV-b and Cannabis. We are going to carry out a research study using UV-b on Cannabis (replicating the study by Lydon, Teramura, and Coffman, 1987), so it may be worth while for us to first write up a 'state of the art' research review on UV-b for higher plants, and for Cannabis specifically.

shaggyballs · Sep 23, 2014

Beta Test Team said:
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.

Hey lets get your post count up ...LOL...Question:
Do plant have different lighting requirements in the morning than at noon/mid cycle?

Beta Test Team · Sep 23, 2014

Not from any research we've reviewed in terms of quality or quantity when we're only talking about photons and Cannabis photosynthesis.

Cannabis takes about 30 to 45 minutes after the lights are turned on to reach 'steady state photosynthesis' under bright light (for example, 1,000 PPFD). The period between when the lights are turned on and when steady state is reached is called the "lag" period, we want to minimize that time period to maximize radiation use efficiency and plant growth. Therefore using bright light when the lights are turned on is helpful.

So at least for Cannabis a bright morning means the plant reach steady state photosynthesis sooner, which is a good thing in terms of daily net photosynthetic rate (we want to keep that high).

More important than light amount (PPFD) at morning, midday, and evening (assuming it's always >300 and <2,000) is the total PPFD for the entire day (for indoors or supplemental lighting in greenhouses).

For outdoors or natural light greenhouses it's best to average PPFD over a 7 to 14 day period, then use rather complex equation* to find the average per day (accoutring for extraterrestrial irradiance), but realistically, if a outdoor grower measured lux (and converted that to PPFD, or just measured PPFD directly) in the late morning, around noon, and early evening over a period of 3 to 7 days the value (DLI) they come up with will be pretty accurate and very useful.

* IA[a + (bn/N)]

shaggyballs · Sep 23, 2014

Beta Test Team said:
Not from any research we've reviewed in terms of quality or quantity when we're only talking about photons and Cannabis photosynthesis.

Cannabis takes about 30 to 45 minutes after the lights are turned on to reach 'steady state photosynthesis' under bright light (for example, 1,000 PPFD). The period between when the lights are turned on and when steady state is reached is called the "lag" period, we want to minimize that time period to maximize radiation use efficiency and plant growth. Therefore using bright light when the lights are turned on is helpful.

So at least for Cannabis a bright morning means the plant reach steady state photosynthesis sooner, which is a good thing in terms of daily net photosynthetic rate (we want to keep that high).

More important than light amount (PPFD) at morning, midday, and evening (assuming it's always >300 and <2,000) is the total PPFD for the entire day (for indoors or supplemental lighting in greenhouses).

For outdoors or natural light greenhouses it's best to average PPFD over a 7 to 14 day period, then use rather complex equation* to find the average per day (accoutring for extraterrestrial irradiance), but realistically, if a outdoor grower measured lux (and converted that to PPFD, or just measured PPFD directly) in the late morning, around noon, and early evening over a period of 3 to 7 days the value (DLI) they come up with will be pretty accurate and very useful.

* IA[a + (bn/N)]

So in carpenters terms,start out fast and full throttle on the photons all day long, but no over saturation.

Am I correct?

Is the following info based on fact?

Is far red better for evening/late in cycle?
Blue/UV and (white) better absorbed in the morning and mid cycle?
Or do I have it backwards?

I am trying to get my little brain around this huge topic.....you said to ask. :biggrin:

I'll get that post count up.......you watch! :woohoo:

Thanks
shag

JointOperation · Sep 23, 2014

ive heard of people stacking there rooms with 1000s and 600s.. and having them go back and forth.. 3 hours each.. so u use less electricity in warehouse grows to achieve the same yield?

they say marijuana growers are ahead of there time agriculturally..

doctor.dank · Sep 23, 2014

@Beta test team

What is your take on high end grow bulbs ( hortilux, ushio, etc) vs a $15-30 cheap bulb for mh and hps? Should you go with the cheap bulbs and replace every cycle? Thanks for your input!

Beta Test Team · Sep 23, 2014

shaggyballs said:
So in carpenters terms,start out fast and full throttle on the photons all day long, but no over saturation.

Am I correct?

Yes. But you don't want to provide over about 1,000 PPFD all day unless your environment is VERY controlled. We tend to use 700 to 800 PPFD all day for Cannabis (I didn't include our reasons, as I think I'm typing too much in each post.)

shaggyballs said:
Is the following info based on fact?
Is far red better for evening/late in cycle?
Blue/UV and (white) better absorbed in the morning and mid cycle?
Or do I have it backwards?

No. Far-red isn't something you would want to add to your spectrum normally, unless for very special use-cases (not photosynthesis). And UV-B should be applied all day, like PAR light. (UV-B can be over applied, just like PAR light).

shaggyballs said:
I am trying to get my little brain around this huge topic.....you said to ask.

Yes, please, ask what you are wondering. We may not be able to answer always, but when we can we will.

Beta Test Team · Sep 23, 2014

JointOperation said:
ive heard of people stacking there rooms with 1000s and 600s.. and having them go back and forth.. 3 hours each.. so u use less electricity in warehouse grows to achieve the same yield?

they say marijuana growers are ahead of there time agriculturally..

I don't understand what you're describing. If you can explain more maybe I can offer some input.

Beta Test Team · Sep 23, 2014

doctor.dank said:
@Beta test team

What is your take on high end grow bulbs ( hortilux, ushio, etc) vs a $15-30 cheap bulb for mh and hps? Should you go with the cheap bulbs and replace every cycle? Thanks for your input!

That's not an easy question to answer because it has a few components:

For the brand component:

We don't like el' cheapo lamp brands, the quality control in the manufacturing process is generally quite poor, and the variability of the lamp spectrum is generally high (= bad).

For the spectral component (the light 'color'):

HPS tend to have too much (relative) energy in yellow to red wavelength ranges. But it's not possible to say without analyzing the SPD of your lamps, and that's what the spreadsheet we're writing will do for you, then you can see the possible plant growth potential for your lamp's spectrum.

The quick and dirty answer:

Go with Philips, Eye, or Ushio, and change them after 6,000 to 10,000 hours of use (so, about after every 5th, 6th, or 7th harvest). The best way is to measure light irradiance of the new lamp in your reflector (measure light directly below the lamp), and then measure every few weeks in the same spot under the lamp, and once the light level is around 80% of the starting light level, change the lamp (we're adding features to our spreadsheet to help growers track lamp useful life time).

shaggyballs · Sep 23, 2014

Beta Test Team said:
Yes. But you don't want to provide over about 1,000 PPFD all day unless your environment is VERY controlled. We tend to use 700 to 800 PPFD all day for Cannabis (I didn't include our reasons, as I think I'm typing too much in each post.)

No. Far-red isn't something you would want to add to your spectrum normally, unless for very special use-cases (not photosynthesis). And UV-B should be applied all day, like PAR light. (UV-B can be over applied, just like PAR light).

Yes, please, ask what you are wondering. We may not be able to answer always, but when we can we will.

Great info!!!
Post count almost there!

Anyway
What special case might you need far red for?
It would seem it is all the new LED systems.

Could you give a estimated range for UV-B exposure?
Is UV-B best applied throughout the life cycle?
And would it be supplied at the same intensity in VEG as well as Flower?

Thanks again
shag

Lighting requirement of the cannabis plant.

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