# Liebig's Law of the Minimum



## Hoppy (Dec 24, 2005)

Liebig's Law of the Minimum says that plant growth is limited by the availability of the least available nutrient, not by the total available nutrients. That law applies to light as well as to NPK, but does it apply to the spectrum of light, or the total light? In other words, if a light source is short on red light, does the availability of red light limit the growth, or the total amount of light?

If it is limited by the availability of red light (for example), then you could get the same growth by just using more total light intensity, but, then wouldn't the excess light in other areas of the spectrum encourage algae to grow? And, if that is the case, wouldn't a "perfect" spectral distribution of light be a good way to discourage algae?


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## BruceF (Aug 5, 2011)

These kinds of generalizations are tricky. Too much calcium can harm some plants while others will be fine. Some plants need more light than others and some plants can take advantage of light in certain spectrums while others can’t. 
Just because you limit the light doesn’t mean it is a limiting factor for all plants. Having hard water won’t bother your vals but it just might kill your crypts. 
I would guess that algae aren’t all that different. Under certain conditions some algae will thrive while others will not.


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## Hoppy (Dec 24, 2005)

The more important question, I think, might be, do algae use the same parts of the spectrum as plants? Or, do various types of algae preferentially use different parts of the spectrum?


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## BruceF (Aug 5, 2011)

I think you are going to find that all the types of chlorophylls, carotenoids and such are found in algae just as they are in plants.


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## jeffdenney (Jun 21, 2013)

Ive been wondering about this as well. More with light spectrum. Im not hip yet on what plants require more of which nitrients. I dose a slightly modified ei fwiw. 

Ive had a diy led setup for almost a year now and i am always messing with the spectrum. I recently turned down my reds and blues very low (20%) and left my whites at the same level(65%). Most of my gsa has stopped growing and some bba on my spraybar has slowed significantly. Plants seem to actually be growing faster..


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## jeffkrol (Jun 5, 2013)

Hoppy said:


> The more important question, I think, might be, do algae use the same parts of the spectrum as plants? Or, do various types of algae preferentially use different parts of the spectrum?


I like to use a lake as an example.. It can be "balanced" for decades w/ higher and lower plants.. then pour a few tons of phosphate in there and ..bam.. algae everywhere..

Light didn't change (initially, until the floating algae starts to block it)....

any ecosystem has "tipping points" where one species or another will out-compete a co-inhabitant.

I don't consider light to be a major tipping point.. more likely nutrient imbalance, pH or choice of plants (that don't thrive well under the above).........though light can seem to control to a certain degree...


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## Hoppy (Dec 24, 2005)

If I have a tank with an ordinary LED light, with a strong peak in the blue -green area, but little in the red area, with a PAR reading at the substrate of 50, and another tank with a PAR reading at the substrate of 50, but with a LED light with a lot of violet-blue and dark red in the spectrum, will plants grow equally fast in both tanks?

I keep thinking it would be a very interesting experiment to make a couple of LED lights, each with enough dark red LEDs and violet-blue LEDs so they can give a PAR of about 40 at the substrate in 5 gallon tanks, plus enough white LEDs to give either an unbalanced white PAR 40 or a white with added red and blue PAR 40. Then set up two 5 gallon tanks identical except for the light spectra being used. Then test a violet-blue only set-up, a dark red only set-up, a unbalanced white spectra and a more balanced white spectra, to see what a couple of plant species do. When I move to an apartment, with less room to do DIY stuff, I will think more seriously about doing this.


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## jeffkrol (Jun 5, 2013)

Hoppy said:


> When I move to an apartment, with less room to do DIY stuff, I will think more seriously about doing this.


you would be better off baffling a tank to split it in 2 and hanging different lights over each side.. 
Keeping the 2 separate tanks nutrient/CO2 equal would be difficult...


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## jeffdenney (Jun 21, 2013)

jeffkrol said:


> you would be better off baffling a tank to split it in 2 and hanging different lights over each side..
> Keeping the 2 separate tanks nutrient/CO2 equal would be difficult...


True dat. baffles would have to b black so light pollution wouldn't b an issue.


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## jeffkrol (Jun 5, 2013)

jeffdenney said:


> True dat. baffles would have to b black so light pollution wouldn't b an issue.


Plenty of black plastic in the world..
Some fun reading:
http://www.hortamericas.com/grower-...-grow-lights/led-grow-light-case-studies.html

none are using "white" LED's.. 

http://www.hortamericas.com/images/pdf/philipsGreenPowerLED/PURDUECS.pdf

Of course few want a "purple" fish tank.. 

http://growblu.com/led-grow-lights-perfect-spectrum

all of which is why I lean to a mix of RB(deep blue):Cyan(blue and green):CW(mostly visual , some blue):WW(mostly visual, short red):660nmRed(long red).. covers all the "bases"... 
someday I may even consider adding farther red:
http://biology-forums.com/index.php?action=gallery;sa=view;id=356










come to think of it.. that may be why I "feel" that removing my "warm white" LED's was not as productive as my current 6500k ones.. Less 700nM red..


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## jeffdenney (Jun 21, 2013)

Good reads. Thanks


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## Hoppy (Dec 24, 2005)

jeffkrol said:


>


Unless the light intensity is kept constant, you get "synergy" just by increasing the intensity, when you leave both of those colors of light on. A good researcher would, of course, know that and probably did keep the intensity constant.

Also, when measuring oddball light spectra like this, an Apogee PAR meter is very inaccurate, so you either need a Li-Cor PAR meter, or do some very careful adjusting of the Apogee meter readings.


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## DarkCobra (Jun 22, 2004)

I've read that red light, in particular deep red, is a better stimulator of red coloration (anthocyanin production) than other parts of the spectrum. So if you want a certain amount of red coloration, by providing more deep red light, you may be able to achieve the desired pigmentation with less light overall. Which should in general make it easier to control algae.


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## jeffkrol (Jun 5, 2013)

Hoppy said:


> Unless the light intensity is kept constant, you get "synergy" just by increasing the intensity, when you leave both of those colors of light on. A good researcher would, of course, know that and probably did keep the intensity constant.
> 
> Also, when measuring oddball light spectra like this, an Apogee PAR meter is very inaccurate, so you either need a Li-Cor PAR meter, or do some very careful adjusting of the Apogee meter readings.


Even assuming "additive" in the graph.. eyeballing shows 33% +33% = 95%..


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## DarkCobra (Jun 22, 2004)

jeffkrol said:


> all of which is why I lean to a mix of RB(deep blue):Cyan(blue and green):CW(mostly visual , some blue):WW(mostly visual, short red):660nmRed(long red).. covers all the "bases"...


Let's say I want to construct a small LED "cluster", to be repeated any number of times as necessary. I want it to look and function as much like natural sunlight as possible, but with the following restrictions. It would include cyan, and 660nm deep red; but only ONE type of white. And NO supplemental royal blue, only what the white produces.

In this case, which white would you recommend? And assuming each color is on a separate dimmable channel, approximately what power ratios of white/cyan/red might be needed?


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## jeffkrol (Jun 5, 2013)

DarkCobra said:


> Let's say I want to construct a small LED "cluster", to be repeated any number of times as necessary. I want it to look and function as much like natural sunlight as possible, but with the following restrictions. It would include cyan, and 660nm deep red; but only ONE type of white. And NO supplemental royal blue, only what the white produces.
> 
> In this case, which white would you recommend? And assuming each color is on a separate dimmable channel, approximately what power ratios of white/cyan/red might be needed?


Personally. I'd recommend 3500K... 
The power ratios are a bit tricky due to the point source nature of the LED's and some "appear" brighter..

My first build was w/ 3=10W 10000K/actinic hybrid chips 2= 10W 660nm red and 15=1w 3500K (NO color correction or post processing besides boosting overall exposure in camera BTW)










Selectively dimming the red (which I currently run 0-full then full to zero at the end of a ramp cycle, and to be honest isn't well blended during "daylight period" ATM)

In th above picture you can see the 2 red 3 hybrid chips w/ the "yellow" being the 15 LED string.. Point here is you need to run enough to "blend" and not worry so much about absolute values..

My current design, using 3W LED's is this.. It is in the "alpha" stage and subject to major revisions but it will run 4 channels
1)mixed whites 2)red 3)cyan and 4 is variable w/ either royal blue or mixed white/royal blue. Using the 4 channel Typhon controlleer you can ram up and down ansd "Set" a max output per channel, so I'm more concerned w/ "disco" effects than which channel gets what power..
royalblue/cyan/deep red "clusters" are supposed to yield "white".. I'll find out soon...  
i'm also thinking about using 4 "strips" which can be put togehter in an "arc" fashion in order to overlap the cones better... I also thought of turning them upside down and building a large 'mixing chamber" but too much work.. NOT very scientific nor completely without warts.. but it was a fun learning experience. Tomorrow when the lights are back on I'll get a current picture.. It has had its ups and downs (I'm not very attentive) over the past months.. but it has been interesting.. Personally lighting may be my "fun" but it is the other bits that are probably a lot more important.. i.e nutrients ect..Lets face it you can grow plants and fish w/ incandescent bulbs.. 



















BTW: The idea came from LEDGroupbuy w/ the OCW (oceancoralwhite)
http://www.ledgroupbuy.com/ocean-coral-white/
HMM.. seeing they are on sale right now, to be honest, I don't think it will be any cheaper for me to order the parts separately.. THAT is a bit of a bummer, since most are already ordered.. 


> We recommend 4-6 of these boards per 24x24x24 area.


well that would raise the price... 

Pretty much a RB/Cyan/deepred fingerprint:


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## jeffkrol (Jun 5, 2013)

DarkCobra said:


> It would include cyan, and 660nm deep red; but only ONE type of white. And NO supplemental royal blue, only what the white produces.
> 
> In this case, which white would you recommend? And assuming each color is on a separate dimmable channel, approximately what power ratios of white/cyan/red might be needed?


Rereading your post made me rethink my other babbling post.. 
I guess I'd try 10000k white... As long as you are going to use an equal count per color per cluster. OR.... 

just put 2 whites on one channel and cyan and red in a cross pattern, using one "warm" one "cool" K values will sum (and then divide)
Say a 10000K white and 3500K white of the same output (relatively speaking, generates a 6750K effective output.. 

If you want a warmer look.. dim the cyan, cooler, dim the red.

If you look at my early "build" photos there is a good collection of the individual channels.. to give you a feel for it.. 
Actinic/10000k full power.. no other channels:








3500k "white"









660nm red... Put the 3 together and the pic is in the prev post............









Kind of "magical"........... 

Power of dimming:









BASICALLY mixing RGB...........just like your monitor... 

CORRECTION the "red" does have the warm white on a bit.. Never took a photo of "just red".. seemed pointless..


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## DarkCobra (Jun 22, 2004)

That does help. I'm mainly wondering about the "headroom" necessary for the supplemental colors, for producing various shades of white only. IE, it would be wasteful to put a 10W white and 10W red on, if I'll never run the red at more than 2W.

I just got my first DIY LED up and running over a 20G tank, literally 30 minutes ago. Each "cluster" has 3W of CW, NW, WW, and RB, and it has two clusters, I'll be adding a third since shadows are a bit deeper than expected. Controlled by a custom four-channel dimmer, MCU, and wireless connection. No external controls whatsoever, and haven't yet got the wireless working, so for now I just hardcoded a soft start into it, ending in a 4:4:2:1 default ratio. Not bad looking. But I can't wait to get it fully controlled so I can play, and I'm already thinking about new things to try on the next fixture.


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## Greystoke (Jul 24, 2010)

I've been interested in this for quite a while, unfortunately I could never find much on this on the internet, except two articles which I like to share:

Giving plants the right amount of light
Effects of LEDs on leaf lettuce

A lot of this confirms what we already know (not sufficient I think). It did however convince me that we should give more attention to the *RED/BLUE* ratio AND the *RED+BLUE*(PAR) minimum level or as a percentage of the total PAR level.

One point that bothers me is the fact that the "photosynthetic active radiation" is not restricted to 400 - 700nm, but more likely to 350 - 750nm.


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## FlyingHellFish (Nov 5, 2011)

I been hearing that PAR isn't exactly the great measurement we think it is. The measurement should be in PUR (Photosynthetic Usable Radiation), rather than PAR.


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## jeffkrol (Jun 5, 2013)

DarkCobra said:


> That does help. I'm mainly wondering about the "headroom" necessary for the supplemental colors, for producing various shades of white only. IE, it would be wasteful to put a 10W white and 10W red on, if I'll never run the red at more than 2W.


Not really a real figure BUT say "red" is 5x more efficient photosynthetically than "neutral white" how would it be wasteful??? In my own tank I run red "high" when I'm at work, then ramp it down. 


DarkCobra said:


> I just got my first DIY LED up and running over a 20G tank, literally 30 minutes ago. Each "cluster" has 3W of CW, NW, WW, and RB, and it has two clusters, I'll be adding a third since shadows are a bit deeper than expected. Controlled by a custom four-channel dimmer, MCU, and wireless connection. No external controls whatsoever, and haven't yet got the wireless working, so for now I just hardcoded a soft start into it, ending in a 4:4:2:1 default ratio. Not bad looking. But I can't wait to get it fully controlled so I can play, and I'm already thinking about new things to try on the next fixture.


Insidious isn't it...


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## Greystoke (Jul 24, 2010)

FlyingHellFish said:


> I been hearing that PAR isn't exactly the great measurement we think it is. The measurement should be in PUR (Photosynthetic Usable Radiation), rather than PAR.


I also think so, although we came a long way from Watts/gallon :wink:


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## Hoppy (Dec 24, 2005)

FlyingHellFish said:


> I been hearing that PAR isn't exactly the great measurement we think it is. The measurement should be in PUR (Photosynthetic Usable Radiation), rather than PAR.


From what I read, PUR isn't an absolute measurement. Different plants utilize the various wave lengths of light in different proportions. So, how would a PUR meter be able to work? (Not to speak of the enormous cost of one for a hobbyist!)



Greystoke said:


> I've been interested in this for quite a while, unfortunately I could never find much on this on the internet, except two articles which I like to share:
> 
> Giving plants the right amount of light
> Effects of LEDs on leaf lettuce
> ...


Those are interesting articles, especially the first one. I can see how PAR readings can substitute for a more wave length accurate "PAR" reading, but if you start experimenting with blue or red lights, you would be under estimating the intensity of the light you were using if you limited it to 400-700 nm PAR readings. In other words a "blue" light source could produce a higher growth rate per unit PAR than white light primarily because you were ignoring the large amount of light just outside the 400 nm limit of PAR meters.


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## Hoppy (Dec 24, 2005)

The point of my question about Liebig's Law is that if plants need a certain minimum amount of red light, for example, and we add more light that doesn't contain any appreciable red in the spectrum, will the plants growth rate be limited by the absence of enough red light? Has anyone tried growing plants using only an actinic bulb as a light source?


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## UDGags (Sep 13, 2009)

Yes, rate will change but the plants I bet would adapt and the rate would change over time.

Sent from my DROID BIONIC using Tapatalk


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## jeffkrol (Jun 5, 2013)

Hoppy said:


> The point of my question about Liebig's Law is that if plants need a certain minimum amount of red light, for example, and we add more light that doesn't contain any appreciable red in the spectrum, will the plants growth rate be limited by the absence of enough red light? Has anyone tried growing plants using only an actinic bulb as a light source?


Another yes, though short in duration:


> The results of two independent fluence-rate/response experiments using over 60 seedlings are shown in Figure 5A and 5B. Figure 5A shows the height of seedlings grown for 72 h under constant blue light and Figure 5B shows the effect of the same treatment with red light.





> It is of great interest to not only to foster plant growth, but to control plant growth. Basic plant research has demonstrated that specific light wavebands may affect discrete aspects of plant physiology, such as germination [19], stem growth [20], biomass [15, 21, 22] and the transition to flowering [23]. The supplementation of specific wavebands or skewing of overall spectrum may help modulate the progression of these developmental events.


http://link.springer.com/article/10.1186/1471-2229-5-17/fulltext.html#Sec2_62

Of course a "blue" tank is no more desirable than a purple or red one..

Interesting:
http://cpl.usu.edu/files/publications/publication/pub__4124704.pdf

.


> Overall, the low blue light from warm white LEDs increased stem elongation and leaf expansion, whereas the high blue light from cool white LEDs resulted in more com-
> pact plants. Initial growth under cool white LEDs should promote the growth of short, sturdy hypocotyls. Subsequent transition to warm white LEDs should promote leaf ex-
> pansion. Finally, after canopy closure, cool white LEDs should be used again to prevent excessive stem elongation


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## Black Pearl (Jul 23, 2013)

Doesn't it always go back to "sunlight." Any artificial lightsource that simulates the "sunlight cycle" (sunrise to sunset) is best. Although, some plants prefer shade while others full sun.


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## DarkCobra (Jun 22, 2004)

jeffkrol said:


> Not really a real figure BUT say "red" is 5x more efficient photosynthetically than "neutral white" how would it be wasteful??? In my own tank I run red "high" when I'm at work, then ramp it down.


That's very energy efficient. But my current goals are along the lines of sunlight mimicry, to enhance real and perceived plant color.


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## jeffkrol (Jun 5, 2013)

DarkCobra said:


> That's very energy efficient. But my current goals are along the lines of sunlight mimicry, to enhance real and perceived plant color.


sunlight when???? 

anyways just for fun a current pic.. from back of tank , some ambient light 

100:50:100 "Bluewhite"/red/6500k in "watts" terms it would be more like 30/10/15....though the blue white is under driven...

There are colored shadows, I haven't tried to eliminate them w/ this build.. 











frog:
One of 3 african frogs ...forgive the really bad pictures.. afew nerites..a few asst snails


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## Hoppy (Dec 24, 2005)

Black Pearl said:


> Doesn't it always go back to "sunlight." Any artificial lightsource that simulates the "sunlight cycle" (sunrise to sunset) is best. Although, some plants prefer shade while others full sun.


Intuitively, that is correct. But, unless that is verified by experimenting, it is just intuition.


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## Black Pearl (Jul 23, 2013)

Hoppy said:


> Intuitively, that is correct. But, unless that is verified by experimenting, it is just intuition.


It's verification is life. These plants have been using (and have adapted to) light from the sun since time immemorial. 
Having said that, I guess one can experiment on using different wavelenghts/color of artificial light and maybe get different color and/or growth characteristics. Who knows, given enough time, maybe one can create a new plant life entirely. Plants adopt and life finds a way.


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## jeffkrol (Jun 5, 2013)

DarkCobra said:


> That's very energy efficient. But my current goals are along the lines of sunlight mimicry, to enhance real and perceived plant color.


That can be mimicked by "just white" .. as to actual continuous spectrum.. well that is another story.. 



















Oh and good luck.. 









Even the solar spectrum is not "smooth"............. but since much of this is 1)unwanted i.e UV, IR and much is "atmospheric absorption" some comes into play even in your house.. 

Oh and if plants were totally "efficient" they would appear black, absorbing every quantum of light they could get...........
In other words neither plants nor sunlight are efficient in "human" terms......... 

IF evolution was "efficient" Mammals would possess chlorophyll.. Oddly enough we are quite close to that:








http://science2be.wordpress.com/2012/09/03/the-amazing-similarity-between-blood-and-chlorophyll/
http://en.wikipedia.org/wiki/Protoporphyrin_IX


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## Greystoke (Jul 24, 2010)

Hoppy said:


> From what I read, PUR isn't an absolute measurement. Different plants utilize the various wave lengths of light in different proportions. So, how would a PUR meter be able to work? (Not to speak of the enormous cost of one for a hobbyist!)


Comes to the push . . . you could calculate the PUR output of a light source if the spectrum and the efficiency of the light is known. Of course, that wouldn't be very practical, and - I agree - trying to measure it would be a mission.
I also don't like expensive toys, which maybe "nice to have" but are not in frequent use.

If - in my opinion - you could measure the RED output (600-700nm) as well as the BLUE output (300-500nm) in photons/m²/s, then you could work out the R/B ratio and the R+B output to secure the plant's minimum requirements.
Once established, you can add "other" light to improve "looks", without affecting RED and BLUE.


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## DarkCobra (Jun 22, 2004)

jeffkrol said:


> IF evolution was "efficient" Mammals would possess chlorophyll.. Oddly enough we are quite close to that:


I never knew that! That's amazing.

I just discovered the "buildmyled" website. As I prefer to "builditmyself" I never checked it out before.  But they have an impressive design tool. After playing with it for a while, I managed to configure a light source with 5625K (very near sunlight), minimal spectral gaps, and 97CRI; using 10x 4000K white, 1x 470nm blue, 2x 505nm aqua, and 1x 660nm deep red.

Now the trick is to scale it down so that each cluster is under 10W total output, without each cluster being too expensive. I can spring for top quality Cree/Luxeon on the white emitters, but it's all the other colors that concern me, as I only need a little of each by proportion. I wonder if there's any reliable name-brand 0.25-1W LEDs. Or if cheap no-name 3W LEDs will run without significant losses long-term when massively underdriven.


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## jeffkrol (Jun 5, 2013)

DarkCobra said:


> I never knew that! That's amazing.
> 
> I just discovered the "buildmyled" website. As I prefer to "builditmyself" I never checked it out before.  But they have an impressive design tool. there's any reliable name-brand 0.25-1W LEDs. Or if cheap no-name 3W LEDs will run without significant losses long-term when massively underdriven.


 About time.... 

StevesLED's has good though not cheap "aqua" (cyan,turquoise,) but 3W...1W cyan are currently hard to find.. The rest are all available cheap at fleabay.. The 3W are not much more than 1W.. Careful w/ fleabay as manuf. have bundled blue/yellow LED's and selling as "cyan" . The 2 peaks add to cyan but are not cyan...


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## jeffkrol (Jun 5, 2013)

DarkCobra said:


> I never knew that! That's amazing.


One of my scarey thoughts that led me not to pursue a career in genetics........ 
The world isn't ready for green people..


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