Advanced light cycle

[Bubbleblower]

I would enjoy reading anything you have to share.

Personally I am much more interested in what you, Shaggy or Ornamental have to share. You are smokers like me, open minded and not here for donations.

What about far red led's putting out far red after they are off?

Mmm, you'd suspect they would. Still not a fan of using FR leds though as the footprint would be very small and the light possibly not strong enough.
May be that is why this is not true at all:

Shaggy, "End-of-day treatment" is also a common use for far-red LEDs

This is, same as what Only Ornamental said:

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).

The “critical period” is after the lights go out.

Is timing of exposure important?

Very much.

I just wonder if we are over saturating our plants in the morning and in the evening.

Midday depression:
http://books.google.nl/books?id=0_3XqlcKPpwC&pg=PA288&lpg=PA288&dq=midday+depression+plants&source=bl&ots=yQGRkFjI20&sig=VTLAzHKxWoVVBmlRXj6IOOIOsYs&hl=nl&sa=X&ei=0-ZIVM78HIm-PbDngPgC&ved=0CCEQ6AEwAA#v=onepage&q=midday%20depression%20plants&f=false

 

[Beta Test Team]

Far red only induces an 'immediate' nightfall for the plant.
Plants measure the night-length with phytochromes to compare actual day/night lengths with the internal clock so that they know for example when to flower. These light-sensing proteins have two configurations depending on presence of red (visible) light and absence of light, respectively. In the morning with the first light, it takes mere minutes to turn the phytochromes into the non-signalling 'day' state whereas after sunset it takes 2-4 hours of complete (visual) darkness until the light-activated phytochromes spontaneously turn back into the signalling night-state. In order to reduce this lag time, the phytochromes can be quickly converted to the night form by irradiation with far red light (near infrared). A sunset is often orange because red light bends stronger in the atmosphere than blue and once it's visibly dark, there's still far red light present which helps the plants to actively convert the inactive phytochromes (called Pr for 'phytochrome - red light') into the active night state (called Pfr for 'phytochrome - far red light').
Notably, irradiating phytochromes with red and far red light at the same time will turn them into the Pr or day-form.
Using far red LEDs after lights out does exactly the same like a sunset but faster; switching the phytochromes from Pr to Pfr within minutes.
In an indoor setting, switching off the lights removes, depending on the bulb type, immediately all light including far red and the phytochromes can only spontaneously and hence slowly turn into the night form. That means, using a 12/12 light schedule on your timer is perceived by the plant as roughly 15/9. In nature, the night starts shortly after sunset and hence outdoor hemp starts flowering at a critical day-length of about 14 hours (tropical cannabis a bit later in season). In other words, indoor flowering cannabis gets 12 hours of photosynthesis whereas outdoor crops get two hours more.
Bottom line is, by using far red LEDs on lights-out one can use longer days during the flowering cycle (e.g. 14/10) and hopefully get fatter buds .

Hello there I've read some of your past posts, nice to see other scientists here.

I think it's important to make the point that what you wrote about is not what this thread is about (at least as I understand the thread). Far-red EOD treatment is separate from the proposed lighting schedule, I think.

Not only phytochromes, but also cyrptochromes likley control flowering induction (response) in all species of Cannabis, though for some genotypes it's to a lessor degree (like autoflowering). And phototropin may also play a role.

Another important point is the R:FR ratio and its effects on plant stretch (from shade avoidance reactions). As I wrote in other threads, the R:FR ratio for the sun is about 0.6 to 0.8 in the morning and evening, and about 1.0 to 1.2 during the rest of the day. So if one uses a far-red EOD treatment, which isn't required with most HPS and MH lamps, it's important to not go too extreme or plants will stretch...

Furthermore, PPE (phytochrome photoequilibrium, aka PPS; Pfr/Ptotal) is a better way to quantify effects from red and far-red in terms of phytocrhome, rather than R:FR ratio.

Using far-red EOD treatment doesn't require PAR radiation to be turned off. Using far-red EOD can be as simple as adding a few incandescent lamps to a grow room and turning them on for the last 20 or 30 minutes of the 'day' while the PAR radiation source is still operating. This is good as it allows for very accurate far-red EOD treatment, assuming the spectral quality of the light sources are known and analyzed...

Do you happen to have data on your last paragraph claims specific to Cannabis? I know that claim is often made about Cannabis but I have never seen facts to back up the claim. For example, some genotypes can naturally flower at 10 hour night period; I have used between 12.5 and 13.5 photoperiods for flowering tests in the past (hydrbid cultivars) and I always use greater than 12 hour photoperiod for flowering. There is good research on this for Cannabis, showing the strong effect from increasing photoperiod by only 15 or 30 minutes from 12 hours (for drug biotypes).

 

[Beta Test Team]

What about far red led's putting out far red after they are off?
overloading the plant.

LEDs are not like incandescent lamps in that way (as far as I know, I'm no expert on LEDs). So after you turn off the LEDs they should not emit radiation (though I could be wrong...).

See what I wrote to Only Ornamental about far-red EOD for more info.

For LED arrays far-red LEDs would be required to fulfill the plants PPE requirements, unless there's other source for far-red radiation. And the reason LEDs can be used (and often are used) for far-red EOD treatments is often minimal photon flux density (umol/m2/s) is needed to affect PPE for many low-radiation requirement crops.

Midday depression of photosynthesis is often misunderstood, and seems to have been in this thread, too. Midday depression of photosynthesis happens due to various reasons, most commonly from high irradiance and high VPD in the middle of the day outside. That doesn't really have much to do with this thread, as I"m sure you will control your VPD in your room (keep temp and RH in ideal ranges) and not cause photoinhibition from too great irradiance (specific wavebands can be more of an issue than others, like yellow).

 

[Beta Test Team]

Opps. Didn't mean to post this.

 

[Beta Test Team]

In nature, the night starts shortly after sunset and hence outdoor hemp starts flowering at a critical day-length of about 14 hours (tropical cannabis a bit later in season).

Just wanted to mention that Cannabis sativa L. (fiber and drug biotypes alike) are long-night flowering plants (as far as I know). Often Cannabis is mistermed a 'short-day flowering' plant, but it's not, because it's the nightlength that matters, not the daylength. So it's a 'long-night flowering' plant.

So for Cannabis, we are talking about the "critical nightlength" not "critical daylength." I.e. for most genotypes of Cannabis to flower the critical nightlength for that genotype must be exceeded for a few days in a row to initiate flowering.

This matters when one uses greater or less than 24 hour diurnal period.

 

[Beta Test Team]

I almost like being wrong more than right Absorbs better. I would enjoy reading anything you have to share.

I'm still looking for the one reference I wrote about, once I find it again I'll post it. But this may be good for now, showing why strong radiation all day may be better than less strong all day:


From "Handbook of Cannabis" (about $140):
http://ukcatalogue.oup.com/product/9780199662685.do

Biosynthesis of THC, and the accompanying essential oils in cannabis, demands especially high amounts of energy. The amount of energy required to biosynthesize terpenoid molecules has been calculated to be up to three times greater than that required to synthesize an equivalent weight of sugars (Gershenzon 1994).

From "The propagation, characterisation and optimisation of Cannabis sativa L.":
http://www.gwpharm.com/uploads/finalfullthesisdjpotter.pdf

Even on the brightest days, when outside light levels reached 85 klux or more, the supplementary lighting was activated when outside light conditions fell below 60 klux - this always being the case in the early and late part of the day. The amount of total light energy to which plants were exposed daily was thus greatly increased.

The new lighting regime also significantly improved the uniformity of monthly average yields over the year (F-test, p = 0.013).

However, despite this there was still some seasonal variation in yield. The average THC-chemotype summer yield (harvested May – October 573 g m-2) was significantly greater (ANOVA, p < 0.001) than that of crops harvested over the rest of the year – 516 g m-2. In theory, further increases in supplementary lighting would have increased winter yields

 

[Beta Test Team]

Also, just the other day I read research while working on our spreadsheet that explained how there was no benefit to your proposed lighting schedule (I don’t recall the research specifics off hand, but I think it was on Cannabis). Your proposed schedule has been tested by scientists in the past, in growth chambers, but not on Cannabis, and has not been found to be beneficial (which is why it’s not used in professional horticulture). I will find the specific information for you tomorrow.

I almost like being wrong more than right Absorbs better. I would enjoy reading anything you have to share.

Found it (See the screenshot)

From:
"Plant Growth Chamber Handbook" (Chap. 1., page 24)
http://www.controlledenvironments.org/Growth_Chamber_Handbook/Plant_Growth_Chamber_Handbook.htm (all chaps are as PDFs)

 

[Only Ornamental]

Hello there I've read some of your past posts, nice to see other scientists here.

I think it's important to make the point that what you wrote about is not what this thread is about (at least as I understand the thread). Far-red EOD treatment is separate from the proposed lighting schedule, I think. You got that right. I was merely answering to Shaggys remark in a simple way considering the most frequent use (at least on this side of the ocean) of far red light .

Not only phytochromes, but also cyrptochromes likley control flowering induction (response) in all species of Cannabis, though for some genotypes it's to a lessor degree (like autoflowering). And phototropin may also play a role.
They may. From what I've read (and I didn't read everything ), cryptochromes are implicated in the circadian rhythm but not flowering. Because cannabis is a short day plant (Yes, SHORT DAY, not long night; though scientifically not correct, that's the term used by convention/tradition) we still lack a lot of knowledge. What we know is primarily based on rice... maybe not the best plant to extrapolate...

Another important point is the R:FR ratio and its effects on plant stretch (from shade avoidance reactions). As I wrote in other threads, the R:FR ratio for the sun is about 0.6 to 0.8 in the morning and evening, and about 1.0 to 1.2 during the rest of the day. So if one uses a far-red EOD treatment, which isn't required with most HPS and MH lamps, it's important to not go too extreme or plants will stretch...

Furthermore, PPE (phytochrome photoequilibrium, aka PPS; Pfr/Ptotal) is a better way to quantify effects from red and far-red in terms of phytocrhome, rather than R:FR ratio.

Using far-red EOD treatment doesn't require PAR radiation to be turned off. Using far-red EOD can be as simple as adding a few incandescent lamps to a grow room and turning them on for the last 20 or 30 minutes of the 'day' while the PAR radiation source is still operating. This is good as it allows for very accurate far-red EOD treatment, assuming the spectral quality of the light sources are known and analyzed...

Do you happen to have data on your last paragraph claims specific to Cannabis? I know that claim is often made about Cannabis but I have never seen facts to back up the claim. For example, some genotypes can naturally flower at 10 hour night period; I have used between 12.5 and 13.5 photoperiods for flowering tests in the past (hydrbid cultivars) and I always use greater than 12 hour photoperiod for flowering. There is good research on this for Cannabis, showing the strong effect from increasing photoperiod by only 15 or 30 minutes from 12 hours (for drug biotypes).
It's common knowledge that European fibre/seed hemp has a critical DAY length (I hate that 'wrong' term as much as you but it's the one being commonly used and means the same ) of roughly 14 hours. I do have some literature somewhere on my computer but don't know where. Though, temperature and total irradiation (forgot the correct term, it's not my field of expertise after all) play a role as well. You'd have to search pubmed, sciencedirect or alike...

Thanks for the details and taking over the nitpicking... that used to be my part, you know .
Seriously, I appreciate you taking the time for the explications I was too lazy (and not sure enough) to go into.

 

[Only Ornamental]

Just wanted to mention that Cannabis sativa L. (fiber and drug biotypes alike) are long-night flowering plants (as far as I know). Often Cannabis is mistermed a 'short-day flowering' plant, but it's not, because it's the nightlength that matters, not the daylength. So it's a 'long-night flowering' plant.

So for Cannabis, we are talking about the "critical nightlength" not "critical daylength." I.e. for most genotypes of Cannabis to flower the critical nightlength for that genotype must be exceeded for a few days in a row to initiate flowering.

This matters when one uses greater or less than 24 hour diurnal period.

It still is a short day plant because that's the term commonly used. As this term doesn't indicate what the plant measures or to what it responds but merely at which day length (and therefore night length as well, they always add up to 24 hours*) they flower it isn't really wrong, just not super accurate...
Science is only right so long as not proven otherwise and common terms often take a long way to get replaced.

*Unless you're more crazy than me . But where's the point in days of more or less than 24 hours? Remember, plants usually do best at that one or in some cases at a multiple of 24...

 

[Only Ornamental]

...like autoflowering...

'Autoflowering' is a term which does not exist outside the 'toker jargon'.
It is also very wrong as it implies flowering independent of a flowering signal commonly (again, based on tradition and convention) referred to as 'florigen'. The proper term is 'day-length independent' (or if you will 'night-length independent') as it still requires the plant to be at a certain developmental stage, age, and/or size . There's just no inhibition of the flowering signals caused by too long (or short) nights.

Sorry, but I just couldn't help it! Don't take it personally, okay?

 

[Beta Test Team]

Ha, good point about short day (though you won't win me over)

We don't use atypical diurnal period, though I have tested in the past with Cannabis, as have some other people that are also crazy and like wasting time.

In terms of time to flowering and temperature, for example from day 1 of germination, ADT can be an important factor to speed plant growth. The greater ADT (to a point, around 27'C) the quicker the plant is likely to begin flowering (assuming radiation quality isn't a variable). But higher ADT means (for at least many ornamental flowers) smaller flowers and reduced flower number.

Cryptocrhome has been found to play a role in flower induction (time) for a while now, how this relates exactly to our plants of interest is unclear, as your point about rice is a good one, but I think it's safe to assume CRY1 and/or CRY2 are able to affect flowering Cannabis sativa L. However, in we're inferring from rice, maybe not (see the tomato study). That said, I agree with your overall point: it's phytochromes that control photoperiodism of Cannabis as it relates to flowering:

Manipulation of the Blue Light Photoreceptor Cryptochrome 2 in Tomato Affects Vegetative Development, Flowering Time, and Fruit Antioxidant Content
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC548851/

Light signals and flowering
http://jxb.oxfordjournals.org/content/57/13/3387.full.pdf

The Cryptochrome Blue Light Receptors
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3155252/

 

[Beta Test Team]

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

'Autoflowering' is a term which does not exist outside the 'toker jargon'.
It is also very wrong as it implies flowering independent of a flowering signal commonly (again, based on tradition and convention) referred to as 'florigen'. The proper term is 'day-length independent' (or if you will 'night-length independent') as it still requires the plant to be at a certain developmental stage, age, and/or size . There's just no inhibition of the flowering signals caused by too long (or short) nights.

Sorry, but I just couldn't help it! Don't take it personally, okay?

I'll raise you in correct vernacular, as long as you don't take it personally either )). The exact term you're looking for is: "day-neutral"

Cannabis sativa L. is a "quantitative short-day plant," or said another way, a "facultative long-night plant." And some of its varieties and cultivars are closer to "day-neutral," like the autoflowering types.

However, "autoflower," like "short day," although incorrect, are now sadly the terms used by most people. See attached screenshot from "Handbook of Cannabis" for an example from well respected scientist, Dr. David Potter*:

* http://www.clear-uk.org/dr-david-potter-the-biology-and-benefits-of-cannabis/
* http://www.gwpharm.com/management-team.aspx

 

[Only Ornamental]

Right, there's also the term day-neutral.
I couldn't find anything useful regarding these in the scientific literature... Most don't even mention, let alone investigate, them likely because they lack a control mechanism.
I wouldn't count Potter as a reference in this regard . I fear he's starting to become too focussed on the canna-bizz and the money which can be made with it (obviously, a good part comes from tokers) might cloud his objective/scientific/non-profit judgement.

Hmm... just found a publication I downloaded a while ago about chrysanthemum responding also to blue light (or rather blue light inhibiting flowering under long day conditions). But the underlying mechanism seems more likely to be mediated by phytochrome A and B than cryptochromes; though, the researchers themselves are unclear about it. Research is ongoing they say... couldn't find a follow-up publication...

One big problem with scientific investigations is the artificial environment and the often non-physiological conditions employed. Though very valuable for studies on a molecular level these are too often useless for growers/farmers insofar that it's unclear how to translate the findings from controlled lab settings into an every day field/garden/grow-room setup.

 

[Bubbleblower]

LEDs can be used (and often are used) for far-red EOD treatments

Ok, if you insist.
Please show us one example then where this is common practice.



It would be nice if we could find relevant research about light intensities in relation to midday depression.
Me, I am convinced a gradual schedule would increase the photo inhibition point.

Figure 16.1 on the first page here shows we want to maximise the time period untill “steady state photosynthesis” is reached.
We probably need tons of tests to work out which dynamic schedule works best under what conditions with what plants.

 

[Beta Test Team]

Right, there's also the term day-neutral.
I couldn't find anything useful regarding these in the scientific literature... Most don't even mention, let alone investigate, them likely because they lack a control mechanism.
I wouldn't count Potter as a reference in this regard . I fear he's starting to become too focussed on the canna-bizz and the money which can be made with it (obviously, a good part comes from tokers) might cloud his objective/scientific/non-profit judgement.

Hmm... just found a publication I downloaded a while ago about chrysanthemum responding also to blue light (or rather blue light inhibiting flowering under long day conditions). But the underlying mechanism seems more likely to be mediated by phytochrome A and B than cryptochromes; though, the researchers themselves are unclear about it. Research is ongoing they say... couldn't find a follow-up publication...

One big problem with scientific investigations is the artificial environment and the often non-physiological conditions employed. Though very valuable for studies on a molecular level these are too often useless for growers/farmers insofar that it's unclear how to translate the findings from controlled lab settings into an every day field/garden/grow-room setup.

Correct, right now science just don't know enough, and it's hard to study these things properly.

For day-neutral plants like tomato, cry has been found to affect flowering time. And for long-day (short night ) plants like A. thaliana it has as well. However, the big question (and the answer may be no) is if cry affects short-day flowering plants like Cannabis. And if we infer from rice (a quantitative short-day plant, like Cannabis), maybe not, but if we infer from chrysanthemum (a qualitative short-day plant, unlike Cannabis genotypes), maybe. Hmmm...

Cry2 has been found to inhibit PhyB inhibition of flowering, at least in A. thaliana from my passing read of an abstract.

Often when there is not enough scientific evidence or fact to make a clearly correct statement, we like to assume yes or no, when there's a bit of evidence either way. In this case it seems the evidence points to maybe yes.

By the way, I have enjoyed our chat here. You're quite smart

 

[Beta Test Team]

Bubbleblower, until you learn how to quote in full context I won't respond to you. It's kind of too bad, because I know the answers to your questions that would help others (e.g. irradiance and MDD of photosynthesis).

P.S. Re-read your citation a few times and you'll find some answers. That work is very good, we have had it for some time now...

 

[Riddleme]

I am currently playing with an odd schedule to see if I can see a change in midday depression. My current grow is a breeding seed run so I have no worries about yield and I am running my flower lights at 6.5 on, .5 off, 4 on, 13 off to see what I see?

It just started so I'll report back if there is any thing significant?

 

[shaggyballs]

You're quite smart

You're quite smart, I'll say!

This guy seems to have his hand in everybody's cookie jar..LOL

He is sharp....through, not flawless, I would think he is one of the most intelligent people I have ever encountered!

And his knowledge base is vast!

Like E.F. HUTTON......for us older American folks.
(investment commercial)
"When E.F. hutton talks people listen"...ROF.....LOL

Shag


Edit:
Beta is no slouch either, for sure.

 

[Beta Test Team]

I am currently playing with an odd schedule to see if I can see a change in midday depression. My current grow is a breeding seed run so I have no worries about yield and I am running my flower lights at 6.5 on, .5 off, 4 on, 13 off to see what I see?

It just started so I'll report back if there is any thing significant?

Just wondering how you're quantifying any change and why you think your plants experience midday depression of photosynthesis?

 

[HUGE]

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