# Phytochrome/Infrared Interaction



## Kief Reefer (Dec 25, 2007)

Infrared light converts the form of phytochrome from PFR to PR, with 
critical levels of PR triggering the hormone tentatively called 
florigen. Would a slightly higher temperature level at night increase to 
conversion of PFR to PR during flowering? If so, what is my margin of 
error? The last part of the question is that, why have studies shown a 
stronger response to temperatures being ten to fifteen degrees cooler 
at night if the given above is true?


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## skunkushybrid (Dec 28, 2007)

Excellent thread, and something that I have only very recently started looking into. 

What i do know is that if you veg' with the red end of the spectrum then using infra red would reverse the growth effects of the plant, and overemphasise them if you are vegging under blue.

There is also a school of thought that suggests infra red reflects off plants and they use this to judge their surroundings... although it seems more likely that they take in the IR and the amount they get allows them to guage the surroundings.

I would like to know more... why is the pfr to pr conversion so important, if you wouldn't mind?


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## sgtpeppr (Dec 28, 2007)

I don't know anything about this yet, but it seems from what was posted in the first thread that IR helps the plant grow faster....at least that what I got out of it. If that were the case I think IR at all times would be helpful. It may just be that this stuff seems so advanced because when people first started growing indoors they never considered all of the different energy available in light. I think ultimately and ideally we could find a way in which to use every wavelength of light for the benefit of growing the plant to its maximum potential. Of course we could just believe that the plant already knows this information and how to use it and just supply it with everything we are capable of reproducing. Basically give it everything and let it decide what to do with the stuff it cannot use. Which if you think about it is probably what happened with the whole UVB to THC thing.

Of course as Your Grandfather says "This is just my opinion and I could be wrong about all this"


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## sgtpeppr (Dec 28, 2007)

*******************************************************************************************
There are a couple posts with a lot of technical/scientific reading...so you can skip down four posts and read the outcome*
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From Wikipedia, the free encyclopedia*

*Phytochrome* is a photoreceptor, a pigment that plants use to detect light. It is sensitive to light in the red and far-red region of the visible spectrum. Many flowering plants use it to regulate the time of flowering based on the length of day and night (photoperiodism) and to set circadian rhythms. It also regulates other responses including the germination of seeds, elongation of seedlings, the size, shape and number of leaves, the synthesis of chlorophyll, and the straightening of the epicotyl or hypocotyl hook of dicot seedlings.
*Isoforms or states*

Phytochromes are characterised by a red/far-red photochromicity. Photochromic pigments change their "colour" (spectral absorbance properties) upon light absorption. In the case of phytochrome the ground state is Pr, the r indicating that it absorbs red light particularly strongly. The absorbance maximum is a sharp peak 650&#8211;670 nm, so concentrated phytochrome solutions look turquoise-blue to the human eye. But once a red photon has been absorbed, the pigment undergoes a rapid conformational change to form the Pfr state. Here fr indicates that now not red but far-red (also called near infra-red; 705&#8211;740 nm) is preferentially absorbed. This shift in absorbance is apparent to the human eye as a slightly more greenish colour. When Pfr absorbs far-red light it is converted back to Pr. *Hence, red light makes Pfr, far-red light makes Pr. In plants at least Pfr is the physiologically active or "signalling" state. *

Summary of the characteristics of plant phytochromes:
Purified Cph1 phytochrome in the Pr state (left) and the Pr/Pfr mixture (right) that is formed by irradiation with red light. Since daylight contains a lot of red light, during the day phytochrome is mostly converted to Pfr. At night, phytochrome will slowly convert back to the Pr form. Treatment with far-red light will also convert Pfr back to Pr. Since plants use red light for photosynthesis, and reflect and transmit far-red light, the shade of other plants also can make Pfr into Pr, triggering a response called shade avoidance. In most plants, a suitable concentration of Pfr stimulates or inhibits physiological processes, such as those mentioned in these examples.
Since both the ground state Pr and excited state Pfr are unusually stable (Pfr has a half-life of hours or days) the quantum nature of this transition was not immediately recognized. These two forms are therefore commonly (though technically incorrectly) referred to as isoforms.

*Biochemistry*
(deleted some info about the cell from here)
The Pfr state passes on a signal to other biological systems in the cell, such as the mechanisms responsible for gene expression. Although this mechanism is almost certainly a biochemical process, it is still the subject of much debate. It is known that although phytochromes are synthesized in the cytosol and the Pr form is localized there, the Pfr form, when generated by light illumination, is translocated to the cell nucleus. _*This implies a role of phytochrome in controlling gene expression, and many genes are known to be regulated by phytochrome, but the exact mechanism has still to be fully discovered*_. It has been proposed that phytochrome, in the Pfr form, may act as a kinase, and it has been demonstrated that phytochrome in the Pfr form can interact directly with transcription factors.

*Discovery*
Using a spectrograph built from borrowed and war-surplus parts, they discovered that red light was very effective for promoting germination or triggering flowering responses. The red light responses were reversible by far-red light, indicating the presence of a photoreversible pigment.
In 1983 the laboratories of Peter Quail and Clark Lagarias reported the chemical purification of the intact phytochrome molecule, and in 1985 the first phytochrome gene sequence was published by Howard Hershey and Peter Quail. By 1989, molecular genetics and work with monoclonal antibodies that more than one type of phytochrome existed; for example, the pea plant was shown to have at least two phytochrome types (then called type I (found predominantly in dark-grown seedlings) and type II (predominant in green plants)). It is now known by genome sequencing thatOpenDNS has five phytochrome genes (PHYA - E) but that rice has only three (PHYA - C). While this probably represents the condition in several di- and monocotyledonous plants, many plants are polyploid. Hence maize, for example, has six phytochromes - phyA1, phyA2, phyB1, phyB2, phyC1 and phyC2. While all these phytochromes have significantly different protein components, they all use phytochromobilin as their light-absorbing chromophore. In the late 1980s, the Vierstra lab showed that phyA is degraded by the ubiquitin system, the first identified natural target of the system to be identified in eukaryotes.
In 1996 a gene in the newly sequenced genome of the cyanobacterium _OpenDNS_ was noticed to have a weak similarity to those of plant phytochromes. Jon Hughes in Berlin and Clark Lagarias at UC Davis subsequently showed that this gene indeed encoded a _bona fide_ phytochrome (named Cph1) in the sense that it is a red/far-red reversible chromoprotein. Presumably plant phytochromes are derived from an ancestral cyanobacterial phytochrome, perhaps by gene migration from the chloroplast to the nucleus. Subsequently phytochromes have been found in other prokaryotes including _Deinococcus radiodurans_ and _Agrobacterium tumefaciens_. In _Deinococcus_ phytochrome regulates the production of light-protective pigments, however in _Synechocystis_ and _Agrobacterium_ the biological function of these pigments is still unknown.
In 2005, the Vierstra and Forest labs at the University of Wisconsin published a three-dimensional structure of the photosensory domain of OpenDNSphytochrome. This breakthrough paper revealed that the protein chain forms a knot - a highly unusual structure for a protein.

*Genetic engineering*

Around 1989 several laboratories were successful in producing (_transgenic plants_) which produced elevated amounts of different phytochromes (_overexpression_). In all cases the resulting plants had conspicuously short stems and dark green leaves. Harry Smith and coworkers at Leicester University in England showed that by increasing the expression level of phytochrome A (which responds to far-red light) shade avoidance responses can be altered. *As a result, plants can expend less energy on growing as tall as possible and have more resources for growing seeds and expanding their root systems*. This could have many practical benefits: for example, grass blades that would grow more slowly than regular grass would not require mowing as frequently, or *crop plants might transfer more energy to the grain instead of growing taller*.


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## sgtpeppr (Dec 28, 2007)

This is from an Eastern Connecticut State University page here
unfortunatly the pictures would not load for me

phytochrome has two different chemical structures that are inter-convertible. The forms are named by the color of light that they absorb maximally: Pr is a blue form that absorbs red light (660 nm) and Pfr is a blue-green form that absorbs far-red light (730 nm). What is strange about these pigments is that when they DO absorb these photons, they change chemically into the OTHER form. This is shown in the following diagram which you should commit to memory: *

Pr** red light Pfr
660 nm
&#8594;
  &#8592;
730 nm
far-red light  *



You can see the relationship between chlorophyll and phytochrome, both have evolved from a tetrapyrrole ring system also seen in the phycobilin pigments of bacteria. The chromophore is bound to a protein, just as in the case of chlorophyll. The protein has a mass of 165 kilodaltons. What is interesting is how the chemical structure of phytochrome is altered to its complementary form when struck by photons of the correct energy level (wavelength!).

The plant maintains higher levels of phytochrome at its growing points where phytochrome plays important roles in growth responses to light.

Phytochrome initiates different responses by the plant at different photon flux densities in terms of the environmental signal perceived. These are classified as: *VLFR* (Very Low Fluence Responses), *LFR* (Low Fluence Responses), and *HIR* (High Irradiance Responses). Thus phytochrome can elicit correct behavior for the lighting conditions found in the plant's environment

*Phytochrome can alter the rate of elongation in plants*

The growth rate of plants is dependent on their genotype and the environment, as you know from any introductory course: 
*Phenotype = Genotype + Environment*

Phytochrome works this way too. Here are some environmental conditions: 
PFD µmol m-2 s-1 R/FR ratio 
Day 1900 1.19 
Sunset 26.5 0.96 
Under Canopy 17.7 0.13 
5mm deep in Soil 8.6 0.88 


(I really wish the picture for this one showed up)
As you can see, the canopy species responds to the light available in shaded environments by growing rapidly, and remains compact while in full sun.


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## sgtpeppr (Dec 28, 2007)

The team, funded mostly by the National Science Foundation, determined that phytochrome is twisted into a molecular knot, an uncommon shape for any protein. The scientists theorize the knot helps give phytochrome an overall stability as it snaps back and forth between two different forms in response to changes in light color

"Scientists have long known that this protein snaps back and forth between shapes in response to changes in light color," said Michael Mishkind, a program officer in NSF's biology directorate. "Now for the first time they have obtained a glimpse of the structure of this molecular switch at the atomic level."
According to Mishkind, plants sense and interpret patterns of light quality and duration to ensure their life cycles and growth patterns stay in step with periodic and unexpected environmental changes.



Following is from here

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*
"This is probably the most important light regulator in agriculture," says Richard Vierstra, a UW-Madison plant geneticist and one of two collaborating senior authors of the Nature paper. "It tells plants when to germinate. It tells them where to grow to absorb the most light and to avoid competition. It tells them when to flower. It tells them when to die at the end of the growing season."*
********************************************
*
According to Vierstra, there are many kinds of phytochromes found in every plant, and they exist in virtually all cells. They occur in greater concentrations in cells that respond directly to light, such as in root tips and new shoots.


Intriguingly, the phytochrome has the ability to store the light it has detected, initiating a response days after it is sensed, Vierstra says. "This memory allows the plant to predict where the light will come from each day and measure the length of daylight so that they flower in the correct season.


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## sgtpeppr (Dec 28, 2007)

The plants seem to prepare themselves to respond to light while still in the dark, by synthesizing a couple of closely related proteins (FHY3 and FAR1) that boost the synthesis of other two closely related proteins (FHY1 and FHL), essential factors involved in the plant's reaction to light. 

"The plant probably stockpiles these proteins needed for light responses in the dark for the same reason that a traveler fills his car's gas tank the night before a morning journey: in order to be able to get going, without delay, at first light." said co-author Haiyang Wang, a member of the research team from Boyce Thompson Institute for Plant Research. 

The plant reacts to light first through light-sensing pigment proteins named phytochrome A, found in the cytoplasm cell and reacting to red light. Light changes the shape of phytochrome A, which permits it to attach to FHY1 and FHL, causing a storing of phytochrome A in the cell nucleus. The activated phytochrome A turns on genes from the nuclear DNA involved in plant growth, flowering, straining and development. 

This has been already known, but the FHY3 and FAR1 connection to reaction to light is a novelty.

The team also found a negative feedback loop between accumulations of phytochrome A in the cell nucleus and the levels of FHY3 and FAR1 proteins: as more phytochrome A is found in the nucleus, less FHY3 and FAR1 proteins are synthesized, and so less phytochrome A enters the nucleus. 

"This feedback loop serves as a built-in brake that limits the flow of light responses," said Wang. 

from here


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## sgtpeppr (Dec 28, 2007)

Now to answer your questions the best I can........



Kief Reefer said:


> Infrared light converts the form of phytochrome from PFR to PR, with
> critical levels of PR triggering the hormone tentatively called
> florigen. TRUE, but from what I can deduce florigen just controls the starting and stopping of flowering.
> 
> ...



Hope this helps


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## sgtpeppr (Dec 29, 2007)

No problem, I just wish I could turn it into something practical.


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## tahoe58 (Dec 29, 2007)

hey sgtpeppr....thats a heady series of posts....prolly have to read through a couple of more times....and then reread again. Keifer - the mere fact that you have brought this topic forward is huge! the added background sgtpeppr has provided adds to the discussion, and will lead us down some paths of debate and inquiry....that in and of itself is instructive. I am enjoying this. Have to digest a little and then maybe have something more interesting to say/ask again? walk on men! this is awesome!


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## sgtpeppr (Dec 29, 2007)

I hope you see something I didn't....I have been racking my brain overnight and all I have come up with is that this is strictly a control/trigger switch for florigen. I have yet to find anything that leads to being able to control it to produce different or better results. Scientists have recently figured out the 3D model of the Phytochrome. Now since I do not have access to sub-atomic cell manipulation devices, I am stuck at a stand still on this one. Plus I don't know chemistry that well....yet. 

Using the 18/6 lighting cycle in veg as an example.....has anyone ever tried spreading that 6 hours darkness throughout the day. Imagine working 18 hour days then going home to sleep for 6, then back to work...that because humans need sleep to survive. Do plants?? What for every 3 hours of light, they got a break for an hour?? Kind of like gradual recovery as opposed to having to recover all at once. Just something to think about.


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## tahoe58 (Dec 29, 2007)

the sleep period has been stated as an important factor....to the tune of a minimum of 11 hours....but I don't know whether or not this answers the question of whether or not this has to be all at once or in bursts....other natural examples include a variety of animals that sleep in short bursts (Canis sp. and Felix sp.). I can certainly atest to the short burst sleeps, asa I have gotten older, I have comer to place where I can turn off (completely) for 15 minutes) and be totally refreshed....though I still do appreciate my full 8 hrs of deep sleep every night as well. Maybe I'm just getting old! hahahahaha


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## Kief Reefer (Dec 30, 2007)

SgtPeppr,

To answer why a higher temperature might work is this: Infra-red light is beyond the human visible spectrum, but not a plants. All energy is in wavelengths, even light energy which is considered a photon, both a particle and a wavelength simoultaneously. What plants "see" as far-red or infrared, we "feel" as heat. It is both technically and essentially identical. We can only feel infra red because our eyes are not adept to the wavelengths in that spectrum, but phytochrome "sees" infrared in the same way it does red. The presence of red light will convert phytochrome to the Pfr form, which in itself triggers other auxins, but not the one in question. Florigen is the hormone for flowering and is triggered by critical amounts of Pr, that is when we turn the lights off there is no more red light to make Pfr, but there will always be infrared light in the form of what we call heat. So all the Pfr converts to Pr and triggers florigen to starts flowering the plant. Where we as guerrilla/indoor/outdoor grower's can go with this information is very limited because of our resources. We can't play with cannabis genetically but we can see the effects of our actions. What would a temperature of 5 degrees higher with a lower relative humidity at night in the flowering room do? What could we deduce from an infrared scan of a flowering room in the day vs in the night? What would it reveal about the amount of heat dispersed in the room? These things I want to know.

To all others, I recently had to sell my whole setup. I've lost my home and consequently had to sell to the garden. I am Picasso with no canvas, Christ with no soul, I AM JORGE CERVANTES WITH NO GARDEN! FUCK!

Ok, I feel better.

To tahoe: Ed Rosenthal says in his book Marijuana Grower's Handbook: Indoor High Yield Guide that studies by independant grower's have shown a cannabis plant will get off to a more vigorous and strong start when vegetated for 24 hours with no dark cycle. Jorge Cervantes says in his Marijuana Horticulture: Indoor/Outdoor Medical Grower's Bible that a cannabis plant's ability to process sugars declines after 18 hours, after which you're wasting light. I would sooner believe Jorge Cervantes, his book is packed with too much info to all take in the first three times you read it, and overall sems more reliable. I myself have noticed a faster start the first week to two weeks under 24/0, at which point I switch to 18/6, veg until flowering. The trade-off is with very picky strains you increase the chance of hermaphrodites. Ed Rosenthal also said a popular technique is to do 24/0 the first week and cut back one hour every week until you flwoer. Jorge Cervantes disregards this technique, calling it amatuerish and totally ignorant of the strains particular needs. Everyone seems to agree optimum flowering time is 12/12 no exception. Numerous studies have been done and there is a lower yield at 11day/13night or 13day/11night.


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## Kief Reefer (Dec 30, 2007)

Oh, and lastly, for the record. Dispersing the 6 hours will cause photoperiod disruptive disorder. IT WILL CAUSE HERMAPHRODITES! DON'T DO IT! I have a personal book which I have collected call Don't Be Stupid. It chronicles every time I killed a plant because i did something stupid, like turn the fan on the plants directly for greater airflow (I was a beginner then, killed 6 of my babies). Also, if you chose to veg for 24/0 during the entire veg state, don't worry about photo shock, or photoperiod disruptive disorder. Only erratic changes in light cycles will do that. You can go straight to 12/12 from 24/0 with no problems at all. Come to think of it, when I wrote the Don't Be Stupid entry for my hermaphrodite, it wasn't a timed cycle, it was erratic. Would a plant be able to sense time cycles? Normally I'd say no, but Sgt Peppr, one of the articles you posted on the first page said that phytochrome had a way of storing light energy within itself for when the plant is ready to "wake up". Could it also adapt to regular cycles of light intermitttently throughout the day? A plant does not need a 24 hour cycle, just a consistent one. I know of a wherehouse in Sweden that has plant on a 16/4 for veg and claim to harvest an entire extra crop every year.


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## sgtpeppr (Dec 30, 2007)

Keif.....excellent responses. I guess my next question is how would you propose adding that extra 5 degrees of heat? I would imagine a IR bulb would be the best and most efficient way of doing this. I don't think this will screw with the photo-resting period at all. I think this is certainly a cheap viable option to try. Then we just need to figure out what the best temp increase is....5 deg, 10 deg..and so on. Anyone who is about to go into flowering want to try this??


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## tahoe58 (Dec 30, 2007)

thanks for your insight. I appreciate the info. I like the idea of 2 weeks 24/0 and then go to 18/6...though again...there are those that argue you only lose time by doing that?

I posed the question some time ago about going to a 12/6 flower schedule and was rebuffed by those that believe the minimum 11 hours of sleep was critical. I have no other supporting evidence personal or otherwise...just what I have ben told so far. I am a scientist by profession and the sleep time makes sense but with the discussion around the phytochrome, it does make me wonder whether or not this learning/preparation capacity would translate into the shorter day of only 18 hrs...the principle being that you could cut 25% of the total time required during flowering....maybe that what those colleagues in the warehouse in Sweden are challenging....? except they trake it one further and go to 16/4 (I am assuming vege - or maybe not....I'm just thinking the shorter daylengths are the trigger for accelerating flowering in natural conditions.

Lots of interesting stuff for sure!


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## Kief Reefer (Dec 30, 2007)

It's an excellent idea, I like the IR bulb, but that would be difficult to measure temperature increase. One thing to do is to pay loads of money to have an ultra-sensitive thermostat... there's gotta be a good way to mark and watch it... Standard space heaters are also not very accurate within 5 degrees. As we all know, anything above 80 degrees will slow growth exponentially, decrease relative humidty but simoultaneously increases the amount of actual water held in the air and opening the possibility for mold and fungus. I wouldn't worry about the humidity if the room is clean, but you would have to keep in mind the 80 degree rule. And temperature's must be taken at the top level of the plant itself. Keep the IR bulb at level with the plant, probably a minimum of two feet away. Keep a fan circulating the air, but on low, we aren't cooling the plants, just making the heat distribution uniform. Here's the experiment: Mark at hourly intervals the temperature in the room. Play with how many IR bulbs it would take, if you're concerned about photoperiod disruption, shade the bulb but allow heat to escape. Keep the heat below 80, coolor during the day and 5 to 10 degrees warmer during the night period. Also, a word for the cautious, do not try this if you think the cops may infra-red scan your house which they are lawfully able to do with minimal indication, and sometimes they do it illegally cause they're all dicks. And I say that being among the 736,000 otherwise law-abiding, taxpaying, americans that were arrested last year for simple possession.


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## Kief Reefer (Dec 30, 2007)

To Tahoe:

The example in sweden was for vegetative. I know that cannabis does require a night period of a specific ratio to it's light period, the 11 hour is not a rule, but a good principle based on a 24 hour circadian cycle. With that in mind, would infra red manipulation encourage shorter night periods during flowering and therefore a full harvest in a shorter period of time? I'd like to think so, but we can only find out from the experiments done by those who have viewed this page and decided to attempt it. What do you think?


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## tahoe58 (Dec 30, 2007)

I agree. Maybe this is something I will do....though I expect I will want to gain some adsditional dirty hands with on-the-job training foirst....certainly something to continue to think about in the near term.


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## sgtpeppr (Dec 30, 2007)

I think I wish I was in a position to test it myself.....damn. I think if the infrared manipulation did encourage more florigen, I would still want the normal 12/12, in the hopes that with the extra time the plant could increase its potential above the normal growth. I would rather have a better plant in the normal time as opposed to more in less time. Even if I were planning on producing large amounts like the Swedish warehouse, I would still prefer quality over quantity.

BTW.....I like the Operation Marijuana for the masses.


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## potroast (Dec 31, 2007)

I don't know if this is relevant, and I haven't checked any of my books, but I thought the hormone, maybe florigen, was always produced by the plant, and destroyed by light. Admittedly, what light I don't know. But anyway, with the uninterrupted hours of darkness the hormone acumulated to a level that signaled flowering, and as long as each night that level was reached, the plant stayed in flowering without interruption.

Hey kief, what about the studies that say decrease in yield with _more than _12 hours light? I haven't seen those. Personally, I give my plants as long a day as possible, while keeping them flowering.

HTH


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## skunkushybrid (Dec 31, 2007)

I'dlike to read these studies too. It doesn't seem logical that giving a plant a longer time to photosynthesise during flower causes a lower yield.

From what i've read about phytochromes, scientists can only recognise 5. Phytochromes also only react to red light, cryptochromes and phototropins react to blue.

So if phytochromes are responsible for flowering, why is it that we can flower under just blue?

phytochromes are responsible for many things, the same can be said for phototropins and cryptochromes.


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## skunkushybrid (Dec 31, 2007)

I forgot to mention that there is also a phytochrome that only reacts to the dark. Could this be the florigen you are speaking of?


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## tahoe58 (Dec 31, 2007)

I think flowering under "just blue" is a function that it might not be "just blue" that just as in the UVB for MH lights there is some.....is it that there may be some red in the "just blue"?


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## skunkushybrid (Dec 31, 2007)

Yes, maybe... but some red is not enough red. It would still mean that the cryptochromes and phototropins would be doing all the growing.

Phytochromes determine a lot of factors, like the plants growth patterns... and if we veg' under red and veg under blue we can see that there are different growth patterns. the main thing I noticed was the leaves, under the blue the leaf edges are more rounded, and sharper under the red. Even the texture of the leaves was different and the colour too. The plants under the red had a darker green, whereas under the blue they were lighter and of a more intense green.

Also, IR actually reverses the growth effects of red light. So to intensify the IR in your grow area should only amount to stunted growth, particularly during flower and flowering beneath a HPS.

Yet, if IR reverses the effects of red light then the same can be said of blue light, in that it reverses the growth effects of red. Yet in this reversal do we assume that the plant stops growing? or merely displays new growth patterns? Is the transition as smooth as that? It would appear so...


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## tahoe58 (Dec 31, 2007)

I found this the other day that has been instructive for me....


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## skunkushybrid (Dec 31, 2007)

tahoe58 said:


> I found this the other day that has been instructive for me....


Thanks tahoe... so the carotenoids do not respond to red light. The chart also shows that plants respond to green light.

Yet green light does not interrupt flowering, at least this is what is said. So if cannabis can still photoynthesise under green light, how is it that we can switch on a green light (not that I do) during flower, and not interrupt the cycle?


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## tahoe58 (Dec 31, 2007)

thats a good question....I do not know the answer...and will think about this a little more now....


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## skunkushybrid (Dec 31, 2007)

I feel the chart also shows that IR is not a good idea. The plant reflects what it can, to increase the IR and force the plant to take in more than it can could do some cell damage.

Heat is something that we are always concerned about, I don't think it's a good idea to put in any more. even during lights out, unless it's too cold of course, then some heating may be in order.


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## Kief Reefer (Dec 31, 2007)

I'm wondering where that chart came from. It is a basic truth, but far from complete. Different wavelengths within a light spectrum actually trigger different metabolic pathways. I studied this last semester. I'm pre-med majoring in Clinical Lab Sciences. Each chlorophyll has many molucules inside that need energy to work, energy in the form of different wavelengths of light depending on which molucule it is. Green light is not absorbed AT ALL but entirely reflected. That's why a green light will not interrupt the dark photoperiod. Wavelengths from 650 nm to 700 nm affect phytochromes, of which there are 5 known, and different plants have different numbers, cannabis has only two, Pr (phytochrome red) and Pfr (phytochrome infra-red). Yellow has little, but some effects on photosynthesis, the molecule if affects I'm not sure. What I am sure is there must be a balance of the lights spectrum. Henk, owner of Dutch Passion Seeds, tells us that a heavy blue spectrum during vegetative growth increases probability of female characteristics. But even a blue light has microamounts of the rest of the spectrum. If you tried blue LED, your plant will die because LED is wavelength specific and does not produce color outside it's specific spectrum. Pr responds to red light present and converts to Pfr. Pfr is, to my knowledge, completely inert and will not trigger hormones, but it does create a biological clock for the plant to know what season it is based on how long the light stays present. Once the light is gone, there is no red light to change Pr to Pfr and Pfr changes back to Pr triggered by infrared light, what we feel as heat, which is always present. Long days does not allow a critical amount of Pr to accumulate at night. I have heard some experts say that florigen is constantly produced, but that the long days do not allow for enough florigen buildup to actually see the results. Some experts say that phytochrome will only trigger the production of florigen with critical amounts of Pr after a long enough light period. I think the latter is more likely. It makes more biochemical sense when one understand metabolic pathways within living organisms.

For SkunkKushybrid:

The plant reflects nothing but green light. It absorbs all other light and in fact has the abillity to take in more than we can dish out. Little Big Way, winner of the 2005 Toker Bowl, grew an 8 foot Afghan Dream with a yield of 4 pounds. He used 4x 1000w Metal Halides on that one plant. We will not cause cell damage by a 5- 10 degree increase at night, especially if the daytime temperature is maintained at 65 or 70. Caretenoids do not respond to red light, but to Blue and Ultra Violet light (between 450nm to 500 nm). Some have debated the importance in UV light. Metal Halides have abundant amounts, but are weaker on the red spectrum. High Pressure Sodium is much stronger on the red spectrum, i.e. why it's a flowering favorite, but has no UV light. Ed Rosenthal sees little difference in yield between the two, but UV light has been proven to increase bud density, if not yield. For this reason, Jorge Cervante suggests a 2MH/1HPS ratio, or a 1/1 ratio for best results.


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## skunkushybrid (Jan 1, 2008)

Yes thankyou... my head's alittle fuzzy today with it being New Years day.

All this does though is explain basic photosynthesis in a more scientific way. Increasing the heat in the flowering area during lights out just doesn't seem like a good idea to me, at least not for my grow space. I'm sure they (the plants) enjoy a nice temp drop during the night. Also this heat would need to be accounted for. Greater attraction to insects for example, mould...

Also one other point, the DP thing... where the guiy says that blue light will make a plant display more female characteristics. What does this mean? That it will still be a male plant but grow like a female?

This doesn't make sense with most seed grows that i have done. I only got caught out once and it was a biggy. The whole crop was the reverse, all the males were female and all the females were male (only 5 plants). What I mean is that usually from the way the plant grows I can tell whether it is male or female from fairly early on. Obviously there are exceptions, but as a generalisation i can tell male from female by growth patterns. There's a reason for this. Males will need to grow taller than females for two reasons that i can think of, the wind and gravity. When the wind hits the pollen gravity will soon take it's place and the pollen will fall downwards. The females are shorter to receive it.

Yes by using light we can alter a plants growth characteristics but I can not believe that this could also cause a plant to display opposite sex characteristics...

Is this DP thing you are referring to do with the work they did on feminised seed?


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## tahoe58 (Jan 1, 2008)

hey Skunk.......just curious why you say this? 


skunkushybrid said:


> ........ _I'm sure they (the plants) enjoy a nice temp drop during the night_. ......


kief....I'll have to go back and dig up the context of that figure. I'll be back if/when I can pinpoint it again....loved your discussion, hihghly helpful for my ole brain! hahahahaha thanks.


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## skunkushybrid (Jan 2, 2008)

Good question... uhm, I think it's because I like a temp drop during the night. I cannot sleep with heating on in my bedroom, and I must have the window open, a tiny crack even in Winter.

Too cold is bad too of course... but I believe that a 10f drop during the night may provide more benefit. Who knows, we need to remember that there are are lots of things scientists still don't know. 

I mean to concentrate our efforts on phytochromes may not be the right direction. Yes we may get increased yields per plant which would be good for commercial growers, but as a hobby grower (and enjoyer of the fruits) I'd rather concentrate on potency, the yields will take care of themselves.

I'd also like to read the paper that says cannabis has only one, albeit interchangeable, phytochrome. 

There is a phytochrome that only reaches critical levels during the dark... and is destroyed by light. Now that sentence rings a lot of bells in my head.


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## skunkushybrid (Jan 2, 2008)

Just thought I'd do a little reading, and I typed this into google: cannabis phytochrome

cannabis phytochrome - Google Search=

This thread is top of the page.


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## skunkushybrid (Jan 2, 2008)

Here's a link to the second on the page...

MARIJUANA OPTICS: An elaboration on the process that makes THC

Done by a guy calling himself Joe Knuc. Fairly interesting read on UVB too.


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## tahoe58 (Jan 2, 2008)

hey Skunk, that's the source work for the original comments made by YGF....gee....I guess its almost a couple of months ago now already eh? wow how time flies.

I am now confuzzled....reference has been made to 5 phytochromes (PhytoA, B, C, D, E), that respond to light/dark. there is some redundancy, but also uniqueness particularly in their absorption spectra. now this is where I get confused, as I understand it each Phyto has two forms (pf anfd pfr). it has been referenced that cannabis has only one phytochrome?

I found this. the molecular biology and biotechnology of flowering (2005 second ed.) - chapter 1 - photoperiodism and flowering......I am reading this now....hopefully, I will unconfuzzle myself....


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## Kief Reefer (Jan 2, 2008)

The idea that cannabis only has one phytochrome was from an AskEd column from Ed Rosenthal on CannabisCulture.com in September 2005. He detailed the effects of red/infrared light and it's effects on phytochrome. It's what originally prompted my question of raising temperatures at night. I'm in the middle of my experiment, but won't see the results for another month or so. For that reason I called on others with this thread to bounce ideas and maybe getting other experiments started. Some research in my botany book referenced five different types of phytochrome, but that different plants have different numbers. It gave an example of two species of pea pods, one had 3 phytochromes the other had 5. Ed Rosenthal only referenced the one type, and I have not come across anything that contradicts him yet. I've seen a lot of people make the assumption that plants will like something because they do. Like sleeping at night. Jorge Cervantes even admits to believing this at first, but his Medical Grower's Bible on page 38 states, "I used to believe a point of diminishing returns was reached after 18 hours of light, but further research shows that vegetative plants grow faster under 24 hours of light." One of our forum members admitted to believing that plants needed sleep cause he did. What I have done is set small ceramic space heaters with a digital temperature set for 75 degrees at night. I try to maintain 70 degrees during the day and am pretty successful at maintaining it. The space heaters kick on at night at keep it slightly warmer. I live in an arid climate and humidity isn't a problem for me. I've just induced flowering simoultaneous with this experiment. The downside is that my control groups were previous crops, I don't have enough room to run simoultaneously an experiment and a control group. I'll have the results starting in a month all the way through harvest.

As far as the Dutch Passion goes, that info was from DUTCH-PASSION, among the archives. Jorge Cervantes adapted it into his book, and lists ways to promote feminine growth. That is, at a certain point in a plants life, sex is determined and it's not at pollination. Jorge Cervantes adds this, "Environmental factors start influencing sex the moment the seedling has three pairs of true leaves (not counting cotyledons)." p. 20 In response to light, he says, "More blue light increases the number of female plants, more red light increases male tendencies."

You said you were more concerned about potency than yield. You should actually consider this approach, then. Research shows that stress on plants may decrease overall yield, but may substantially increase resin production. This is seen with experiments using higher elevations, increased UV production, outdoor stress, water availability. The ability to breed for outdoor and indoor strains has eliminated much of the differences in resin production. It is mostly genetics, but environment can play a strong factor in a higher resin production.


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## Kief Reefer (Jan 2, 2008)

Ok, found the page.


a higher nitrogen concentration will give more females.
a higher potassium concentration will give more males.
a higher humidity will give more females.
a lower temperature will give more females.
more blue light will give more females.
Fewer hours of light will give more females.
It is important to start these changes at the three-pairs-of-leaves stage and continue for two or three weeks, before reverting to standard conditions.

Here's the link:
DUTCH-PASSION


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## tahoe58 (Jan 2, 2008)

wow...thats cool.....thanks for sharing that Kief! cheers!


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## skunkushybrid (Jan 2, 2008)

That article is about feminised seed. I read it around a year ago. Although the piece I read was much longer.

Also this still ignores cryptochromes and phototropins... also what evidence did Ed' supply to back up this 'fact'?


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