Cannabis absorptance spectra: calculated and compared

PetFlora · Sep 25, 2014

3dDream said:
Am I reading your early veg, late veg, early flower, and later flower table right? It looks like the needs don't change.

Think about it, normal outdoor planting takes place in the spring (warm weather) with harvest in the fall (cold weather). The perceived light spectrum changes due to varying distance from the sun

Fruiting and flowering light is redder

I, and several led light companies, compensate by adding a red switch which I engage once buds have set

IMO, this acts like trigger, but is it necessary?

The actual trigger might well be the temperature change

Bubbleblower · Sep 25, 2014

May be we shouldn't add red in flowering, but remove some blue.

Beta Test Team said:
Yep but not off the top of my head, I can find you that info if you need it.

It was very close between Eureka and Redding, so I make that Humboldt and in the south it was an area in South Africa also famous for its cannabis. Nowhere in the world they produce more cannabis than in these 2 places and I found this correlation very interesting.
Both are quite far from the equator at 40°N and 29°S.

Ranger · Sep 25, 2014

PetFlora said:
Think about it, normal outdoor planting takes place in the spring (warm weather) with harvest in the fall (cold weather). The perceived light spectrum changes due to varying distance from the sun

Fruiting and flowering light is redder

I, and several led light companies, compensate by adding a red switch which I engage once buds have set

IMO, this acts like trigger, but is it necessary?

The actual trigger might well be the temperature change

Spring weather is not very different from fall weather, neither being reliably warm or cool, at least not in my area of the Earth. The actual trigger being nocturnal and diurnal timings, I would think.

Point of fact, you can keep cannabis, along with several other species of plants, in vegetation for an indeterminate amount of time, whether changing from blue majority to red majority spectrum's matters not, as long as diurnal and nocturnal timings remain the same.

It might also make for useful information to also realize our sun doesn't put out the exact same color temperature nor intensity from even day to day activities, let alone seasonally, so I would find it hard to subscribe to the theory of color and intensity swing to be much of a factor in "triggering" anything.

Beta Test Team · Sep 25, 2014

PetFlora said:
Think about it, normal outdoor planting takes place in the spring (warm weather) with harvest in the fall (cold weather). The perceived light spectrum changes due to varying distance from the sun

Fruiting and flowering light is redder

I, and several led light companies, compensate by adding a red switch which I engage once buds have set

IMO, this acts like trigger, but is it necessary?

The actual trigger might well be the temperature change

We disagree. Extra red is not necessary to induce flowering or improve flowering, and if it's far-red it's likely unhelpful. Well, that's assuming it's for the photoperiod and not for night-break.

The light spectrum from the sun does not change considerably throughout the season. That's the misunderstanding that is the base of the myth that MH is for veg and HPS is for flowering (which is mostly found in Cannabis growing forums).

In terms of HID, we suggest MH or CMH for all growth stages, as long as goal PPFD and DLI is provided. That's the best way to go in terms of plant growth, especially when we're concerned about secondary metabolites. Assuming the MH isn't all blue, that it has considerable energy through the whole PAR range.

The only reason HPS is better than MH is in terms of converting electricity to PPF. So HPS is more efficient and lower cost to run if we're only considering PPF.

The data we created proves this, for example, that Cannabis doesn't absorb considerably more red in flowering vs. vegetative stage.

To induce flowering Cannabis is a long night plant, so you need to provide greater than about 8.5 hours of darkness for about 3 or 4 days in a row. Cannabis doesn't need 12 hours of darkness, its critical nightlength is around 8.5 to 9 hours.

Cannabis is classified as a "quantitative short-day plant" in academia (even though more correct is "quantitative long-night plant"), so it's the noctoperiod and age of the plant that initiates flowering (which is why "autoflowers" do what they do).

Cannabis does not need vernalisation (low temperature treatment) to flower, and does not respond better to vernalisation when flowering. However, cold temperatures can increase colors of the plant material (due to anthocyanin).

Ranger · Sep 25, 2014

have to respectfully disagree with the notion that cannabis, across the board grouping, only requires 8.5 to 9 hours of darkness to induce flowering. i have personally grown several full sativa varieties that wouldn't flower until the nights were 13 hours minimum. they stayed in veg for 2 months at 12 hours of darkness and were 3 months old when i put them into flower.

also wanted to add i have grown full Indicas at 14 hours of light from seed that stayed in veg for 3 months before i switched them to 12/12, again plenty mature enough to flower but wouldn't until switched to 12 diurnal hours and not less then 10.

PetFlora · Sep 25, 2014

Beta Test Team said:
We disagree completely. Extra red is not necessary to induce flowering or improve flowering, and if it's far-red it's likely unhelpful. Well, that's assuming it's for the photoperiod and not for night-break.

The light spectrum from the sun does not change considerably throughout the season. That's the misunderstanding that is the base of the myth that MH is for veg and HPS is for flowering (which is mostly found in Cannabis growling forums).

In terms of HID, we suggest MH or CMH for all growth stages, as long as goal PPFD and DLI is provided. That's the best way to go in terms of plant growth, especially when we're concerned about secondary metabolites. Assuming the MH isn't all blue, that it has considerable energy through the whole PAR range.

The only reason HPS is better than MH is in terms of converting electricity to PPF. So HPS is more efficient and lower cost to run if we're only considering PPF.

The data we created proves this, for example, that Cannabis doesn't absorb more red in flowering vs. vegetative stage.

To induce flowering Cannabis is a long night plant, so you need to provide greater than about 8.5 hours of darkness for about 3 or 4 days in a row. Cannabis doesn't need 12 hours of darkness, its critical nightlight is around 8.5 to 9 hours.

Cannabis is a classified as a "quantitative short-day plant" in academia (even though more correct is "quantitative long-night plant"), so it's the noctoperiod and age of the plant that initiates flowering (which is why "autoflowers" do what they do).

Cannabis does not need vernalisation (low temperature treatment) to flower, and does not respond better to vernalisation when flowering. However, cold temperatures can increase colors of the plant material (due to anthocyanin).

By red, I mean in the form of a broad 500-630nm warm white with >70% 600+

There are big differences between Indica and Sats in terms of temp variations, intensity of light, color of light, AND, hours of light.

Indicas are derived from cold climates, which typically has shorter and much cooler day light hours; (far from the equatorial sativas where heat and humidity are significantly higher year round are more. Summer light hours ~ 14/10- inter ~ 12/12

Perhaps it's the definition of cold you object to

Ranger · Sep 25, 2014

PetFlora said:
By red, I mean in the form of a broad 500-630nm warm white with >70% 600+

There are big differences between Indica and Sats in terms of temp variations, intensity of light, color of light, AND, hours of light.

Indicas are derived from cold climates, which typically has shorter and much cooler day light hours; (far from the equatorial sativas where heat and humidity are significantly higher year round are more. Summer light hours ~ 14/10- inter ~ 12/12

Perhaps it's the definition of cold you object to

think ya got that backwards amigo, indicas derived from long days, much longer then equtorial strains like sativas, which evolved in short days 13-14 max in "summer" while indacs to the north and south could have days in excess of 17 or 18 the farther you go.

Beta Test Team · Sep 25, 2014

Bubbleblower said:
May be we shouldn't add red in flowering, but remove some blue.

I think we shouldn't be worrying about red vs. blue for flowering. See my post before this one.

I think the red vs. blue for flowering issue is a non-starter. To us, it isn't based in sound science, but we're open to being disproved.

As long as the light provides sufficient PPFD and DLI, and ideally emitting energy over the whole PAR range (as well as far-red and UV-B/UV-A), with a majority in the red PAR region and at least ~10% blue (by % total PPF), it's a fine light source for all growth stages.

Beta Test Team · Sep 25, 2014

Ranger said:
have to respectfully disagree with the notion that cannabis, across the board grouping, only requires 8.5 to 9 hours of darkness to induce flowering. i have personally grown several full sativa varieties that wouldn't flower until the nights were 13 hours minimum. they stayed in veg for 2 months at 12 hours of darkness and were 3 months old when i put them into flower.

also wanted to add i have grown full Indicas at 14 hours of light from seed that stayed in veg for 3 months before i switched them to 12/12, again plenty mature enough to flower but wouldn't until switched to 12 diurnal hours and not less then 10.

Yea, I should have been more clear.

The term "quantitative photoperiodic plant" (such as Cannabis) infers that there is no hard nightlength number to induce flowering. Various things affect the flowering response of such plants, including stress, age, genetics, etc. The opposite, when there is a hard number is called "obligate photoperiodic plant."

Sorry, guess I assumed that was clear from my post when I wrote "quantitative short-day plant," thanks for pointing it out.

What the "critical nightlength" means is plants won't flower without at least that long of a night. It doesn't mean they will only flower with that long of a night. Many varieties will flower really well with only 9 or 10 hours of darkness.

Some plants, such as so-called autoflowers, will flower due to triggers such as age as well.

But on par, it's the nightlength that induces flowering in Cannabis, and that means at least 8.5 hours of darkness per night (for most varieties).

Beta Test Team · Sep 25, 2014

PetFlora said:
Beta Test Team said:

We disagree. Extra red is not necessary to induce flowering or improve flowering, and if it's far-red it's likely unhelpful. Well, that's assuming it's for the photoperiod and not for night-break.

The light spectrum from the sun does not change considerably throughout the season. That's the misunderstanding that is the base of the myth that MH is for veg and HPS is for flowering (which is mostly found in Cannabis growing forums).

In terms of HID, we suggest MH or CMH for all growth stages, as long as goal PPFD and DLI is provided. That's the best way to go in terms of plant growth, especially when we're concerned about secondary metabolites. Assuming the MH isn't all blue, that it has considerable energy through the whole PAR range.

The only reason HPS is better than MH is in terms of converting electricity to PPF. So HPS is more efficient and lower cost to run if we're only considering PPF.

The data we created proves this, for example, that Cannabis doesn't absorb considerably more red in flowering vs. vegetative stage.

To induce flowering Cannabis is a long night plant, so you need to provide greater than about 8.5 hours of darkness for about 3 or 4 days in a row. Cannabis doesn't need 12 hours of darkness, its critical nightlength is around 8.5 to 9 hours.

Cannabis is classified as a "quantitative short-day plant" in academia (even though more correct is "quantitative long-night plant"), so it's the noctoperiod and age of the plant that initiates flowering (which is why "autoflowers" do what they do).

Cannabis does not need vernalisation (low temperature treatment) to flower, and does not respond better to vernalisation when flowering. However, cold temperatures can increase colors of the plant material (due to anthocyanin).

Click to expand...

[FONT=Arial, Helvetica, sans-serif]
[/FONT]By red, I mean in the form of a broad 500-630nm warm white with >70% 600+

There are big differences between Indica and Sats in terms of temp variations, intensity of light, color of light, AND, hours of light.

Indicas are derived from cold climates, which typically has shorter and much cooler day light hours; (far from the equatorial sativas where heat and humidity are significantly higher year round are more. Summer light hours ~ 14/10- inter ~ 12/12

Perhaps it's the definition of cold you object to

I thought you were suggesting Cannabis requires vernalisation* to flower, or flowering initiation benefits from vernalisation. If that's what you meant then I would still disagree.

The ADT (average daily temperature) is important for Cannabis, even when flowering.

Cannabis doesn't use temperature as a flowering trigger, at least as far as science knows currently.

* http://en.wikipedia.org/wiki/Vernalization

Ranger · Sep 25, 2014

Beta Test Team said:
Yea, I should have been more clear.

But on par, it's the nightlength that induces flowering in Cannabis, and that means at least 8.5 hours of darkness per night (for most varieties).

have to agree with everything but that. again i have grown probably 25 varieties of cannabis over the years and have never seen any of them go into flower anywhere near only 8.5 hours of darkness. earliest was First Lady from Sensi, even that required 11.5 hours of darkness to trigger flower.

i have experimented extensively over the years trying to keep electric costs down, by reducing the length of diurnal cycles needed to maintain veg.

Beta Test Team · Sep 25, 2014

PetFlora said:
There are big differences between Indica and Sats in terms of temp variations, intensity of light, color of light, AND, hours of light.

I have not seen any scientific data suggesting different genotypes use light in considerably different ways, for example, our data shows that Afghani (wide-leaflet drug biotype) and Colombian (narrow-leaflet drug biotype) varieties absorb photons in very similar ways in terms of spectrum throughout their entire life.

All the Cannabis varieties (of the same health and N-status) at all growth stages that were analyzed in 1995 through 1998 had very similar absorptance spectra. Cannabis absorbs photons in a very similar manner to other higher C3 plants, and is most unique (in terms of reflection) as compared to similar plants in the range of ±20 nm at 550, 600, and 680 nm, and above 700 nm.

The same is true of PPFD. There have been a few published studies that found PPFD effects on photosynethic rate of WLDB (‘indica’) and NLDB (‘sativa’) were not very different when accounting for temperature effects. That is, the same PPDF for WLDB and NLDB provided similar photosynethic rates.

From all our research we have not seen drastic differences between WLDB and NLDB in terms of light usage, except in terms of nightlength to initiate flowering.

Beta Test Team · Sep 25, 2014

Ranger said:
[FONT=Arial, Helvetica, sans-serif]

Beta Test Team said:

Yea, I should have been more clear.

But on par, it's the nightlength that induces flowering in Cannabis, and that means at least 8.5 hours of darkness per night (for most varieties).

Click to expand...

[/FONT]have to agree with everything but that. again i have grown probably 25 varieties of cannabis over the years and have never seen any of them go into flower anywhere near only 8.5 hours of darkness. earliest was First Lady from Sensi, even that required 11.5 hours of darkness to trigger flower.

i have experimented extensively over the years trying to keep electric costs down, by reducing the length of diurnal cycles needed to maintain veg.

What is the ADT you use in veg and flowering?

We have tested flowering a few different variates (including 'OG' type and Green Dream) at 10.5 hours of darkness and they flowered so well people freaked out at the quality. ADT is between 70'F and 72'F for vegetative stage and 68'F to 70'F for pre-flowering stage.

We have never confirmed that 8.5 hour nightlength claim, it's found in published research from the 1970's.

This seems like a fine area for a research study in 2015!

It's not hard to find the critical nightlength, and it's something we have studied in other species in the past (for University work). I'm putting it on our to-do list for 2015: study Cannabis critical nightlegth.

Ranger · Sep 25, 2014

Beta Test Team said:
What is the ADT you use in veg and flowering?

We have tested flowering a few different variates (including 'OG' type and Green Dream) at 10.5 hours of darkness and they flowered so well people freaked out at the quality. ADT is between 70'F and 72'F for vegetative stage and 68'F to 70'F for pre-flowering stage.

We have never confirmed that 8.5 hour nightlength claim, it's found in published research from the 1970's.

This seems like a fine area for a research study in 2015! It's not hard to find the critical nightlength, and it's something we have studied in other species in the past (for University work). I'm putting it on our to-do list for 2015: study Cannabis critical nightlegth.

my room maintains at between 74-77 ADT the variation stems from my temperature dead band setting on my controller, which i set at 4 degrees with an accuracy of +/- 2 degrees at that setting.

you will find some that flower there and others that flower anywhere across the board at times. i think it would make a good area for some research, at least how it could effect peoples differing needs for their grows and resource usage.

probably the majority of differing times can be traced to the differing levels of sativa and indica hybrids being used for testing. again full sativas can flower at 12/12 but i have found many phenos that needed 13 hours of darkness to flower.

i would look forward to such research for certain.

Beta Test Team · Sep 25, 2014

TerpeneTom said:
A specific brand Lux Meter you recommend?

I was told to suggest to you EXTECH brand, EasyView light meter, model EA30 ("high intensity"). The price is around $150 for the base model:
http://www.extech.com/instruments/product.asp?catid=10&prodid=61

It has ±3 percent 'basic accuracy' for common light sources. Most lux meters have ±5% to ±10% accuracy.

Also, if you want to spend a little extra, get the "EA30-NIST" model, which is the EA30 with calibration traceable to NIST standards. A good thing. Note: that model is about $325.

Here is good info about Apogee quantum sensors, they too have ±3 percent accuracy for common light sources (that aren't rich in >650 nm red light):
"Apogee Instruments Quantum Sensor Technical Information"
http://www.apogeeinstruments.com/apogee-instruments-quantum-sensor-technical-information/

If you have more lux meter questions let me know and I'll relay them to get you an answer.

Bubbleblower · Sep 25, 2014

Beta Test Team said:
I think we shouldn't be worrying about red vs. blue for flowering.

Removing blue as opposed to adding red I meant (in response to the previous post).

I don't worry about spectrums and experiment a lot with them, based on desk research, earlier experience and common sense. But I try to make the biggest improvements by spreading the light and heat better and using intracanopy light.

Also I experiment with stuff like rubisco breaks and adding far red at the end of the light cycle. Supposively an intense exposure to far red light at the start of the night reduces the dark requirement by 2 hours (I suspect that's why HPS does so well).

Beta Test Team · Sep 25, 2014

I'd be interested in reading more about that Bubbleblower, sounds interesting for sure. I can start a new thread for general light treatment experimentation with Cannabis, what do you think? Would that interest you?

That's an area we're interested in as well, including the tangentially related night-break method.

PetFlora · Sep 25, 2014

Beta Test Team said:
I have not seen any scientific data suggesting different genotypes use light in considerably different ways, for example, our data shows that Afghani (wide-leaflet drug biotype) and Colombian (narrow-leaflet drug biotype) varieties absorb photons in very similar ways in terms of spectrum throughout their entire life.

All the Cannabis varieties (of the same health and N-status) at all growth stages that were analyzed in 1995 through 1998 had very similar absorptance spectra. Cannabis absorbs photons in a very similar manner to other higher C3 plants, and is most unique (in terms of reflection) as compared to similar plants in the range of ±20 nm at 550, 600, and 680 nm, and above 700 nm.

The same is true of PPFD. There have been a few published studies that found PPFD effects on photosynethic rate of WLDB (‘indica’) and NLDB (‘sativa’) were not very different when accounting for temperature effects. That is, the same PPDF for WLDB and NLDB provided similar photosynethic rates.

From all our research we have not seen drastic differences between WLDB and NLDB in terms of light usage, except in terms of nightlength to initiate flowering.

Ever seen sats grown outdoors in northern climates or indicas outdoors in the trpoics?

Me neither

Remove your blinders. It takes more than light

HUGE · Sep 25, 2014

I seriously want to thank you for all of this work. This info plus the spreadsheet you are building will be serious weapons. Great shit.

shaggyballs · Sep 25, 2014

Beta Test Team said:
Yes, you're reading it correctly.

For the light needs (as absorption of photons) very little changes in terms of spectrum (there are some changes, but they're all minor). If you want me to I could make up four separate graphs, one for each growth stage, as well as one with all four lines for comparison (there will be some overlap), and upload them here.

We've been meaning to make more graphs from those data but haven't yet, if someone wants them it will give us more of a reason to make them and post them.

Wouldn't take more than 20 minutes or so. Let me know.

Yea!...Yea!....stupid carpenters need their hand held sometimes! :biggrin:

This would take the college course out of the picture for me! :tiphat:

Great new GROUND BREAKING INFO!

By the way I like the new beta, Beta!..LOL

Thanks for spreading such useful and cutting edge info!
shag

Cannabis absorptance spectra: calculated and compared

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