Avoid Misconceptions When Teaching About Plants

Unclepeter · Jan 13, 2011

mean mr.mustard said:
I'm eagerly awaiting an explanation as to why plants without green light do just fine.

I was happy to stay out of the Breeder's Forum when I realized what was to be found for "knowledge".

Just say the word and I'll stay out of this one too.

http://www.oxygraphics.co.uk/whygreen.pdf

Unclepeter · Jan 13, 2011

mean mr.mustard said:
I'm eagerly awaiting an explanation as to why plants without green light do just fine.

I was happy to stay out of the Breeder's Forum when I realized what was to be found for "knowledge".

Just say the word and I'll stay out of this one too.

can you prove to me they do! also if green is the most abundant surely its the one they can store etc... (i'm not sure it is though)

mean mr.mustard · Jan 13, 2011

Time has proven that many cannabis plants have been harvested happily without green light.

I would venture a guess that plants wouldn't store green light as it would be a huge amount of heat... the less voluminous light would be better for storage and adaptation for usage thereof.

I'll leave you to inundate the public with the saving grace of green light.

Meanwhile I'll be out engineering the next green grow bulb.

superpedro · Jan 13, 2011

I'm really curious to what could be the magic you get from green.
After a 14.000m2 field test in flowers, at the PKM greenery in Denmark, they ended up with a better product, and 40% saved energy. They just bought half of the company that made the tests. Thats how happy they were.
Furthermore, with the ability to change spectrum in the circadian rhythm, they can alter the stature and control flowering like never before.

Those lights were developed in collaboration with the south danish university, Ph d's of all trades, and loads of field tests.
They are based on Blue, Red and fRed. They clearly didn't find an advantage big enough to make up for the loss to reflection.

This is in short. Some compact plants with loads of shade growth may actually need green and IR.

So what makes the advantage twice as big as blue or red, and there by better.. Anyone? Spurr??

VerdantGreen · Jan 13, 2011

mean mr.mustard said:
Time has proven that many cannabis plants have been harvested happily without green light.

thats completely different from your assertion that they dont use green light

mean mr.mustard said:
I would venture a guess that plants wouldn't store green light as it would be a huge amount of heat... the less voluminous light would be better for storage and adaptation for usage thereof.

store light??? plants convert light to energy they dont store it.

mean mr.mustard said:
I'll leave you to inundate the public with the saving grace of green light.

Meanwhile I'll be out engineering the next green grow bulb.

i have 10% green in the spectrum of my LED grow light - works great.

when there is already strong white light (mixed spectrum) green light actually drives photosynthesis better than red or blue light

VG

Super.Seeds · Jan 13, 2011

This news about green light and the plants using is starting to worry me!..I always thought green light was unusable to the plants and thats why they sell green headlamps, flashlight, work-lights, etc for working in the grow room during the dark cycle.

Do you think the green light given off from a Bluelab Guardian PH/Temp/EC Monitor is affecting my dark cycle? Is my green LED work-light I use affecting my dark cycle? I need to know this as I run the Guardian 24/7 and I go in during the dark cycle sometimes with the work-light. Thanks!

SS

VerdantGreen · Jan 13, 2011

superpedro said:
....
So what makes the advantage twice as big as blue or red, and there by better.. Anyone? Spurr??

afaik, certain colours such as red reach a saturation point beyond which they just get converted to heat in the leaf rather than sugar/starch. including green gives a whole new 'dose' of light that the plant can efficiently use when it may not be able to use more red. also because green gets partly reflected by leaves it bounces around under the canopy and gets used down there where red and blue tend not to reach...

VG

mean mr.mustard · Jan 13, 2011

I was speaking about chlorophyll using green light in photosynthesis.

I can buy the fact that green light is utilized in carbon fixation.

Read up on chlorophyll storing light.

BTW VG I was speaking to Kopite....

foaf · Jan 13, 2011

I've always cringed with people make such simple statements about such complex systems. I like the article in general, but it really isn't focusing in on the point that the original poster made, the point about green light. The author was just harvesting multiple unrelated misconceptions, such as certain seeds needing to be digested by dodo birds in order to germinate, turns out thats not true.

I'm surprised that they author couldn't find a more recent or specific refereces to validate this statement

It shows that chlorophyll absorbs much red and blue light but little green light. However, accessory pigments absorb green light and pass that energy on to chlorophyll.

the two referenced articles that are the root of that statement are

8.Salisbury, F. B., and C. W. Ross. 1985. Plant Physiology. Belmont, CA: Wadsworth.
22.Hershey, D. R. 1995. Photosynthesis misconceptions. American Biology Teacher 57: 198

The second looks like an article that probably quotes other articles, ie its not a research paper, and the first is a text book.

I'm always sceptical of any scientific statement until I see the actual experiment, and examine the data. Auxillary pigments are well appreciated, and the whole photosynthetic process is being closely examined these days especially since they are trying to use that understanding to help with solar powere and algea based solar fuels. For all you know from this guys statement, the efficiency of passing off excited electrons to chlorophyll might be extremely low, he doesnt say, and so far, I can't find the references he quotes on the internet.

Anyone at a university with a big library? I would be interested to see the references that are in those references 8,22 . If you search the internet, it looks like you can get those on ebooks/pdf, but so far its all a scam to sell something else.

Also, except that colors of light helps trigger different processes in plants, (like converting to flowering)... I don't think that I have ever read or heard that once chlorophyll is excited and able to fuel the production of sugars/starches , that it matters where the excitation comes from.

Being able to use a spectrum of light and needing that spectrum are different things.

headband 707 · Jan 13, 2011

spurr said:
Hey all,

Here are two good articles by David R. Hershey that debunk many wrong ideas in plant science, I especially like the part about green light, etc. I have a few studies showing that green light, under bright (high irradiance) white light (ex. HID) can drive rate of photosynthesis more than blue and red light.

The claims that green light isn't useful is total BS, and based upon flawed 'chlorophyll A/B absorption spectrum' curve passed around the cannabis world for many years (found via. a leaf extract inside a "spectrophotometer"; see this example). That is one major reason I dislike most LED arrays: they lack sufficient green light.

The 'action spectrum of photosynthesis' gives a much better representation of quantum yield from blue, green and red range light than does the 'chlorophyll a/b absorption spectrum'. Albeit the quantum yield of green light from high irradiance white light is undervalued in Kieth McCree's 'action spectrum of photosynthesis' (which is why Keith McCree's work, re: Quantum Flux Density and Quantum Yield Curve, are a bit flawed).

"Avoid Misconceptions When Teaching About Plants"
David R. Hershey
http://www.actionbioscience.org/education/hershey.html

"More Misconceptions to Avoid When Teaching about Plants"
David R. Hershey
http://www.actionbioscience.org/education/hershey3.html

I actually thought the green light was to go into the flower room when the lights are turned off so you can see and that won't trigger hermies??? peace out Headband707

superpedro · Jan 13, 2011

VerdantGreen said:
afaik, certain colours such as red reach a saturation point beyond which they just get converted to heat in the leaf rather than sugar/starch. including green gives a whole new 'dose' of light that the plant can efficiently use when it may not be able to use more red. also because green gets partly reflected by leaves it bounces around under the canopy and gets used down there where red and blue tend not to reach...

VG

I know they use prisms to mix the light from the LED's and emit it as diffuse light. It has a huge effect on the penetration of the red and blue.

And again, they "think" the 50% reflection of green makes it less efficient

So if a leaf is saturated by red, meaning the ATP in the Calvin cycle has to be converted into energy. It should be because of lack of CO2 compared to light intensity - right?
How should energy then help a plant grow more, except by stimulating metabolism by heat?

VerdantGreen · Jan 13, 2011

http://pcp.oxfordjournals.org/content/50/4/684.short

The literature and our present examinations indicate that the intra-leaf light absorption profile is in most cases steeper than the photosynthetic capacity profile. In strong white light, therefore, the quantum yield of photosynthesis would be lower in the upper chloroplasts, located near the illuminated surface, than that in the lower chloroplasts. Because green light can penetrate further into the leaf than red or blue light, in strong white light, any additional green light absorbed by the lower chloroplasts would increase leaf photosynthesis to a greater extent than would additional red or blue light. Based on the assessment of effects of the additional monochromatic light on leaf photosynthesis, we developed the differential quantum yield method that quantifies efficiency of any monochromatic light in white light. Application of this method to sunflower leaves clearly showed that, in moderate to strong white light, green light drove photosynthesis more effectively than red light. The green leaf should have a considerable volume of chloroplasts to accommodate the inefficient carboxylation enzyme, Rubisco, and deliver appropriate light to all the chloroplasts. By using chlorophylls that absorb green light weakly, modifying mesophyll structure and adjusting the Rubisco/chlorophyll ratio, the leaf appears to satisfy two somewhat conflicting requirements: to increase the absorptance of photosynthetically active radiation, and to drive photosynthesis efficiently in all the chloroplasts. We also discuss some serious problems that are caused by neglecting these intra-leaf profiles when estimating whole leaf electron transport rates and assessing photoinhibition by fluorescence techniques.

foaf · Jan 13, 2011

afaik, certain colours such as red reach a saturation point beyond which they just get converted to heat in the leaf rather than sugar/starch. including green gives a whole new 'dose' of light that the plant can efficiently use when it may not be able to use more red. also because green gets partly reflected by leaves it bounces around under the canopy and gets used down there where red and blue tend not to reach.

where do you get that hypothesis from?

the article above is "intra leaf" and it suggests that the chloroplasts near the surface of the leaf reach a point where they are at maximum function secondary to what they state is the weak link, the carboxylation enzyme. In these chloroplasts, no color light can further enhance photosynthesis. Also, that was in sunflowers, I wonder if they have thicker leaves than cannabis, making that effect less of an effect anyway.

Its complicated.

GrinStick · Jan 13, 2011

imho visible light contains all colors of the spectrum and therefore the plant uses it...don't make sense that the plant picks out what colors it uses best.
it may be possible that the green wavelength may 'overdose' or 'inhibit' photosynthesis hence the reason green is reflected partly away; as a measure of protection...
just an opinion, nothing substantial.

VerdantGreen · Jan 13, 2011

couple more links, spurr may have some full text of the above one

http://wwwsoc.nii.ac.jp/jsac/analsci/special/030.pdf

http://www.tutorvista.com/content/b...synthesis/photosynthesis-external-factors.php

superpedro · Jan 13, 2011

VerdantGreen said:
http://pcp.oxfordjournals.org/content/50/4/684.short

Again, a good read about how they/some use green if present.
It doesn't touch the very important reflection loss, probably because it is not a study in how to make growlights..
Every good effect of green should still be considered expensive because of 50% reflection. I want an article that explains it as a general recomendation before I buy it.

It is not science to use an article to support anything besides exactly what it says.

VerdantGreen · Jan 13, 2011

foaf said:
where do you get that hypothesis from. if it isnt from a scientific study or from a notable scientific botanist making an informed conclusion, then you are just propagating the types of misconceptions that this post hopes to dispell. Im not saying that your statement isnt true, but what do you base it on.

.......

last link, the links ive posted on this page should cover my 'hypothesis'

VG

spurr · Jan 13, 2011

GreenintheThumb said:
So do you think that green light can upset the night cycle?

No, it should not, but science still has a lot to learn. The reason it should not is the way plants sense nightlength (and circadian rhythm, in part) is by (at least) far-red light mediated responses (i.e., phytochrome-B; "PhyB", aka Pfr). And there is strong evidence that blue light mediated responses can also play a part in nightlength sensing (e.g., cryptochrome), as well as temperature.

A neat point is that plants have been found to be able to sense when it is 'midnight', see:

"Plants Can Sense Midnight"
Joanne Chory, Howard Hughes Medical Institute (HHMI) (2008)
http://www.hhmi.org/news/chory20080213.html

spurr · Jan 13, 2011

Hempyguy said:
Math-durbators will rise and follow him! The rest will need actual proof.

What the heck are you writing about? I.e., "need proof"? It has been proven many times over plants use ~>50% of green light provided for Pn, and under high irradiance green light can drive Pn better than blue and red.

Here's a tent full of plants grown entirely with 300 watts of LEDs at day 42 of 12/12. They stand 36" tall and the central colas are 18" by 3 1/2 inches. In fact the only thing hold back their height was the top of the tent. It's nice to read and try to understand how things will affect growth and maturation, but in the end experimentation will prove theories right or wrong.

Firstly, this thread is not about LED vs. HID, please don't try making it into such. I wrote I "dislike" LED due to lack of sufficient green, not the LEDs suck.

Also, you are misusing the term theory in a scientific sense; you should have used the word speculation (or more loosely, hypothesis). The scientific theory (i.e., explanation) of how/why plants use green light for Pn is well proven. Many expmients have arleady been conducted by scientists, not some person with a LED chip on their shoulder.

See this thread:
"Fact, Hypothesis, and [Scientific] Theory & How Not to Do Science"
https://www.icmag.com/ic/showthread.php?t=196951

If you like HID's fine! But don't try and and BS others into following you in order to stroke your ego, it's just not right.

I am not sure what you are so upset about. I didn't write anything about HID being better than LED, I wrote (most) LEDs lack sufficient green light; and that's a fact. Can you grow plants without green light? Yes, of course. You can also grow plants without red light, but would you want to? Nope, not if you can avoid it.

Please stop trying to incite a LED vs HID argument in this thread. This is a *science* sub-forum, thus science is welcome, even though you may not like it.

spurr · Jan 13, 2011

mean mr.mustard said:
If you can find chlorophyll that isn't green I'd agree that it uses green light.

That doesn't make sense. There are many accessory pigments to Chl A and B that absorb various colors (wavelength) of photons, for photosynthesis. Also, it's more accurate to write chloroplasts than Chl in terms of photons usage; e.g., green light acts upon lower chloroplasts in a leaf once blue and red light saturate upper chloroplasts in the leaf.

You don't' have to agree with jack, it's well proven that terrestrial plants use green light for Pn.

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