Cannabis absorptance spectra: calculated and compared

[HUGE]

Some questions I have.

What is the optimum ppfd for cannabis? I have heard 1000-1500 umol/sec

What us the minimum/optimum CRI?
100 would be great but where does noticeable loss start.

What is the appropriate amount of UV?
Is there a level or a ratio that is optimum?

 

[Bubbleblower]

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

This is true.

I have not seen any scientific data suggesting different genotypes use light in considerably different ways.

So they have adjusted so well to our less than optimal spectrums, these are optimal now?

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

All the time, sativa's do great here @53N. Sativa's and indica's are the same I think adjusted to different climates.

Some questions I have.
What is the optimum ppfd for cannabis? I have heard 1000-1500 umol/sec
What us the minimum/optimum CRI?
100 would be great but where does noticeable loss start.
What is the appropriate amount of UV?
Is there a level or a ratio that is optimum?

Me too, I suspect all our standard numbers are wrong, especially for cannabis grown from seed (that can handlle a lot more light than clones, guesstimate ~25%).

Also I suspect the appropriate amount of UVB is lower than we think (because all the best cannabis seems to be growing at about the same altitude, any higher doesn't make it higher) and only appropriate if we balance the rest of the spectrum.

From what I remember all the standards were based on solar noon in the tropics, but may be we need it at ~20N and more hours of it. The best growing conditions on earth are at 40N and 29S, but that would be closer to the equator if there would be more vegging time, humidity, sunshine and lighthours.

8.5 hour nightlength claim.

Apparently this depends for a small part on the amount of vegging time and for a large part on how fast the days get shorter after solistice. The faster that is the sooner flowering will start. The pic in my avator shows a DP that started flowering at less than 8 hours nightlength. Many strains here are known to finish in August.

I can start a new thread for general light treatment experimentation with Cannabis.

Good idea, we can discuss many potential improvements from there. A lot of them got nothing to do with light, but could have a lot of effect, like for example containersize. Surely the bigger the container the more light the plant will be able to handle?

 

[PetFlora]

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.

What changes is the distance earth is to the sun: closest in the summer, farthest in the winter, thus changing both intensity and spectrum, as well as temperatures and relative humidity

 

[Ranger]

What changes is the distance earth is to the sun: closest in the summer, farthest in the winter, thus changing both intensity and spectrum, as well as temperatures and relative humidity

indeed they do change and also sun spots, CME's, current solar cycles and so forth all have a direct effect on color and intensity of our sun at any given moment.

i believe what many fail to also remember is that from dawn to dusk sun light intensity varies considerably. so for those attempting to replicate the "optimal" as measured at the equator, amount of light, that it's not "optimal" from dawn to dusk in nature.

for instance we do our best to mimic the suns intensity and color, as far as PAR goes for many hours a day, commonly 18 for veg, but in nature that plant would never have received that much for 18 hours straight.

also i think a lot can be said of color shift adaptation, which many C3 and C4 plants can do and do well. for instance if during a certain time, the sun began to push more red then blue, the plants can adapt to that by varying what they can use more of to accomplish their task.

i know it's common knowledge but it's often over looked how the higher plants can utilize chlorophyll A and chlorophyll B as needed to meet their energy needs. more blue then red, no problem, more red then blue again no problem as they have the ability to derive their energy needs from either side of the spectrum.

i think this data set proves that more then anything else is that there is minimal difference between red and blue utilization, as far as the plants themselves are concerned.

i do however still believe that to get the most out of indoor gardening, one should do all they can to mimic the sunlight they have evolved with for hundreds of thousands of years.

choosing to lean towards just reds or blues would be detrimental to raising the healthiest plants we can. also there is much we need to learn of the roles yellows and to some extent greens play in plant biology.

it is very possible and probable that yellows and greens play a large role in certain terpene productions as well...

 

[Beta Test Team]

I'll post to this thread this weekend, for example, about PPFD and DLI for Cannabis (1,500 PPFD is generally too much for all day).

For now: I do notice that people are posting lots of conjecture as fact.

Remember, just because you think the idea is good and beautiful doesn't mean it's correct. That is what science is for.

People don't seem to quite understand how light traverses the atmosphere (refection off of water, absorption by particles and gases, etc.), and what effects spectrum of the sun seasonally, etc.

I would urge people to read this book so a fuller understanding of sunlight can be gained, as well as a fuller and deeper understanding of issues we're discussing in this thread so we can discuss them more efficiently:

Plants and Microclimate: A quantitative approach to environmental plant physiology
(3rd ed.; free versions can be found online, but it's only $58)
http://www.cambridge.org/us/academi...ch-environmental-plant-physiology-3rd-edition


I'm not saying the few posts above are incorrect, but I am saying they seem to be assuming lots of things as fact that have not been proven as such (at least to our research). And posting data, not only opinion, would very helpful.

Okay, I'll step off the soap box now and get back to our corner working on our data collection spreadsheets.

 

[Beta Test Team]

EDIT: I also see lots of off-topic discussion above, like container size, humidity, etc., can those topics please be taken elsewhere?

Also, let’s stop discussing photoperiodism in this thread, okay? If people are really interested in what makes Cannabis flower, start a new thread and I'll post there, too.

We're not here to disprove anyone, so if people feel like that's what is happening it’s not our intention, that said, it may be a side-effect of posting our data and info here. And we are likely to learn some new things from you all, too

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

 

[shaggyballs]

I agree there is tons of speculation,let stick to the facts,and stay focused to fully understand this complex science.

We all want to know the truth right.
Let this guy prove it with science, if you have scientific eveidence to counter what he states then by all means lets here it.

There are so many threads that get so off topic, the truth is hard to find.
Sorry for the rant!
I just hate wading through the bog to find truth.

shag

 

[Beta Test Team]

Thank you

 

[PetFlora]

When I approached BML regarding their separate grow and flower SPYDRS (@ $999) I wanted to develop a single SPYDR for both veg and flower. My idea was that the 2/6 outside bars would be ~ 600-630 each with an o/o switch to be engaged once buds set

I wanted to provide the ~400-550 range (vegging spectrums) on the inside 4 bars

That was not within their capabilities at that time, so I chose spectrums where each bar had 450 + 6500 + 5000 + 3000 + 625s

I finished a grow that was already 2 weeks into 12/12. Both plants stretched like crazy

I revegged one of them and it is stretching like crazy. selecting one panel that does not account for turning on extra red AFTER buds set, is a problem for many growers who need shorter plants

Before (8/9) and current pics 9/24 under the S600

Note how much the main stalk stretched, even though light was kept within ~ 12", the main stalk is 12" before the branching. This is a waste of height (which most do not have the luxury of n their tents), caused by too much red too soon

This would not happen if I could control when to add the EXTRA reds, which would only be about now

The ideal light allows the grower to add more red AFTER buds set to minimize red spectrum stretch

I am now testing Solar Spec panels, which provides a separate red o/o switch. This allows ME the control over how much stretch to add during veg. Right now I add the red a few hours a day reaching a happy medium for my tent size

View attachment 285621 View attachment 285622

 

[Beta Test Team]

I'm sorry Petflora but I just don't understand what you're writing. Can you be a little more clear?

If you're writing about R:Fr and PPE please take it elsewhere. This thread is about Cannabis absorptance, not shade avoidance reaction and phytochrome issues.

You may like to read my comments on those issues in Shaggy's thread (but please don't respond to these posts in this thread):
https://www.icmag.com/ic/showpost.php?p=6562303&postcount=9
https://www.icmag.com/ic/showpost.php?p=6566274&postcount=17
https://www.icmag.com/ic/showpost.php?p=6566332&postcount=21

Also, the following claim you made is not a fact and has never been found to be scientifically valid (to my knowledge): " ~400-550 range (vegging spectrums)."

Thank you for understanding.

 

[Beta Test Team]

[FONT=Arial, Helvetica, sans-serif]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
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[FONT=Arial, Helvetica, sans-serif].[/FONT]

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

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

You're welcome. But we can't really take any credit, all we did is use the data that other people created to caclaute the absorptance spectra. All the thanks should go to Daughtry & Walthall

We went ahead and re-calculated the mean and made a new mean graph (below). The other four graphs will be done in the next 30 minutes.


Mean of all four analyses throughout the plants' life cycle:

(All of these leaf samples came from healthy nitrogen rich plants at 200 kg N/ha.)

 

[Beta Test Team]

Early vegetative stage (July 5th)

(All of these leaf samples came from healthy nitrogen rich plants at 200 kg N/ha.)

 

[Ranger]

sorry about clogging up your thread, have a good one man.

 

[Beta Test Team]

Late vegetative stage (July 25th)

(All of these leaf samples came from healthy nitrogen rich plants at 200 kg N/ha.)

 

[Beta Test Team]

Early flowering stage (Aug. 14th)

(All of these leaf samples came from healthy nitrogen rich plants at 200 kg N/ha.)

 

[Beta Test Team]

Late flowering stage (Sept. 22nd)

(All of these leaf samples came from healthy nitrogen rich plants at 200 kg N/ha.)

 

[Beta Test Team]

sorry about clogging up your thread, have a good one man.

It's all good

I hope I wasn't rude. It's just that is topic is pretty advanced for most people, so I want to focus on the thread topic, so people can understand and we all can discuss.

What you and a few others are writing is very interesting, and advanced, so I would rather move them to other threads so they can get the attention they deserve. I know many of the topics you, Bubbleblower and PetFlora have brought up interests us greatly. And we intend to carry out rigorous experimentation on Cannabis to test some hypotheses; I hope we can all discuss these topics because it’s very obvious you all are smart and knowledgeable. So there's no lack of interest on our part, I just want to keep the various topics separate, if that's okay.

I will be posting in other threads on the topics you all wrote about, and other threads we will start. Here is a really good published report to that end. It covers many of the important topics you three have brought up - I think you may like it if you haven’t read it yet:

The art of growing plants for experimental purposes: a practical guide for the plant biologist
http://www.publish.csiro.au/?act=view_file&file_id=FP12028.pdf

 

[Bubbleblower]

EDIT: I also see lots of off-topic discussion above, like container size, humidity, etc., can those topics please be taken elsewhere?

Sorry for that, not sure what is on topic then.
Humidity, CO2, temperature and IMO containersize do have a big effect on absorbance spectra and I believe tests should be multivariate. And 3-dimensional

We all want to know the truth right.

IMO we should first accept we never will.

I'm sorry Petflora but I just don't understand what you're writing.

That we should buy these growlights for $999,=.

 

[Beta Test Team]

Oh yea, Ranger, and others, here's a really great review on some of these topics you may like. Such as how yellow can inhibit plant growth (used to be thought green light was the cause, but it's yellow), green light effects on photosynthetic rate, VPD, root space (we use <=1 g/L), etc.

I uploaded for you because it's not free:

Horticultural lighting − present and future challenges

 

[Beta Test Team]

[FONT=Arial, Helvetica, sans-serif]EDIT: I also see lots of off-topic discussion above, like container size, humidity, etc., can those topics please be taken elsewhere?[/FONT]

Sorry for that, not sure what is on topic then.
Humidity, CO2, temperature and IMO containersize do have a big effect on absorbance spectra and I believe tests should be multivariate. And 3-dimensional

On topic is discussing Cannabis absorptance spectra, which isn't greatly affected by VPD, CO2, or container size to our knowledge (please cite published studies if we're wrong).

These plants that were used for the absorptance spectras were grown outside until the leaf samples were taken.

Please read the study I posted in the second post if you haven't yet, if you aren’t familiar with the protocol to find leaf absorptance spectra. Maybe that is a reason why you think some of the things you do about the data we're presenting.

I still think I don't understand what you mean by 3-dimensional.

Anyway, thanks for understanding. And please see the post I wrote to Ranger above this one*, it was meant for you, too

* https://www.icmag.com/ic/showpost.php?p=6572246&postcount=99