Yeah I have a very small finger green light and I have also used it in the dark with no hermies aswell ... peace out Headband707
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Avoid Misconceptions When Teaching About Plants
- Thread starter spurr
- Start date
Yeah I have a very small finger green light and I have also used it in the dark with no hermies aswell ... peace out Headband707
I do not follow you. White light is basically a mix of blue, green and red. So if you had peaks of blue and red, and added green, you would have white light.
mr mustard said:
What do you mean by "less voluminous light"?
Yes, in terms of lower chloroplasts in a leaf.
No, not at all.
I am in my right mind (most of the time, that is); and I claim it is a legit reference. I cited it to show an example of the effect of green light on leaves, I didn't write it will have the same effect on cannabis. My goal was to show that green light has other affects than just increasing Pn under high irradiance.
Avoid misconceptions when teaching about plants.. That is the title of this thread.You have stated the necessity of green LED's in an array as a fact.
I have made no such claim. I never wrote LEDs must have green, I wrote they should have green. There is a big difference between what you claim I wrote, and what I actually wrote.
An example of a valid difference is the latter follows the former. Unless you want to make lamps that are not ideal for growing plants
You are confusing two separate topics: (1) what is best for the plant; and (2) what is best for your wallet (i.e., electricity usage). Just becuase a lamp can grow a plant, while using less energy, does not mean it's the better lamp for the plant.
Yes. If their work is not published, or at least not made public, so we can not judge their work, it has little value. I for one do not trust a company to be unbiased, thus I can't trust what they claim at face value. That is how the world of science works...
And I doubt Phillips horticultural dept. "came up with the HPS"; I would need to read legit proof on that claim.
Just where do you think the "doctors" from the private sector get their knowledge and info they base their work upon? The work by K.McCree is the standard, even today.
I highly doubt as much R&D (e.g., on staff PhDs) goes into horticultural lamps as you like to imagine, if that were the case we would probably have much better lamps by now...
You are writing about efficiency in terms of electric bill, not efficiency in terms of plant growth. I don't know about you, but I want to grow the best plants, regardless of small savings in electric bill.
The simple facts: (1) a light source that offers blue, green, red and far-red is better than the same light source that does not offer all four ranges; (2) plants do not grow better if the eclectic bill is lower; and (3) growing the best plants should be the goal, not growing plants with the lowest electric bill. In terms of a carbon footprint, it's very easy to off-set a growers' carbon footprint by buying carbon credits.
There is no "optimal narrow spectrum" of any light source, this thread is not about LEDs! Science is still learning about photo-reactions in plants, and to claim only a few wavelengths within blue, red and far-red are needed for optimal plants is just crazy. I for one would rather give a broad range of wavelengths, from UV-b to far-red, than give only a few wavelengths based upon flawed studies (i.e., the Chl A/B absorption spectra).
Anyone in their right mind should be using diffuse light verses direct light, but that doesn't help a whole lot for a closed canopy (e.g., SCROG, tight SOG, etc.) in terms of irradiating the lower canopy. The reason is that blue and red light get absorbed by the upper canopy very well, so well in fact, little blue and red makes it intracanopy, in a closed or semi-closed canopy.
I depends on what you mean by "rate". Any high irradiance light source that only offers blue, red and far-red will grow plants better if green is added (esp. under high irradiance like how cannabis is grown; i.e., near or at light saturation point).
Basically, yes; excluding various caveats such as photoinhibition, etc.
A light source with blue, green, red and far-red is better than the same light source with blue, red and far-red (when PPFD is the same, or close; ideally it would be weighed with updated QFD or YPF).
I am only discussing optimal lamps, not most efficient lamps in terms of turning electric watts used into PAR range photons. I care about growing the best plants, not the plants with the least amount of electricity. That said, what I have written is fact, re: plants use green light for photosynthesis.
There is no such thing as scientific fact in terms of explanations, there is only scientific theory (becuase science can be proven wrong); e.g., how/why plants use green light. In terms of a factual statement, such that plants use green light for photosynthesis, it has been found via. many, many studies.
I think this thread should be only about what is best for the plants. That is all I care about anyway, and all the plants 'care' about too.
Just for my own edification, how am I "trying to do it"; re: science? I am "doing" science the proper way, trust me on that, or don't, I really couldn't care less either way.
So, you don't want to "do" science by using published and very highly respected scientific papers? No wonder you don't think I am "doing" science...
I guarantee you every single commercial LED array brand sold to cannabis markets does not have the extensive botanical R&D you are imagining. Most LED arrays only offer blue and red (and a bit of far-red) because the makers used the flawed Chl A/B absorption spectra. LEDGirl comes to mind, as do other LED brands; caveat, I have been informed LEDGirl has added some green to her newest LED arrays.
I did not cite references only supporting my position, which is not a theory. Your lack of understanding about the studies I posted, and how to use said studies, is making it hard to have a rational discussion with you.
If you want to cite legit references that disagree with what I wrote, please do so, I would love to learn if I am wrong about something I wrote.
Here is a good example of an article that could be used against the importance of green light in a LED array, by arguing green light is best used by plants as one directional, from a single light source, and less efficient from diffuse light(we have allot of that from reflection in our growth chambers, or by using multiple light sources. And you can make a light setup specific for diffuse light):
Read this spurr, and if you cant find it in full text, I can help
Holly L. Gorton, Craig R. Brodersen, William E. William, and Thomas C. Vogelmann. 2010. Measurement of the optical properties of leaves under diffuse light. Photochemistry and Photobiology 86: 1076–1083.
Every HID grower using a good reflector is using diffuse light from the pebbled reflective surface. Green light, like other spectra of PAR range, is best provided in diffuse form. I didn't read your citation yet, but, if you have it in full text why didn't you upload it in the first place?
I am not sure you know the difference between diffuse light and direct light. The reason I am unsure is many LEDs (single diodes) emit direct light when the angle of radiance is low; that, and you wrote "one directional", which is confusing in and of itself.
In a closed or semi-closed canopy, you will have little red or blue light intracanopy from diffuse light verses direct light from a single light source (be it an HID or LED array) due to the (small) distance from canopy to lamp.
Far-red light has a very high degree of transmittance through leaves, green has a lower degree of transmittance and blue/red has a very low degree of transmittance through leaves.
Writing about direct light as a reason to not use green light is flawed. Very few growers use a majority direct light out of the total light reaching the plant/s (i.e., irradiance). Under HID and LED arrays there will be direct light, but not a lot of direct light from a good light source.
We should all strive to use diffuse light. A diffuse light source offering blue, green, red and far-red is better than the same diffuse light source offering only blue, red and far-red.
You did not provide any info showing what I wrote is not correct. Just because you really, really, really want green light to be unimportant does not make it so. What I have done (re: references), is used science correctly, what you have done, is not use science correctly.
What makes me confused is why you do not want to learn something new that can help you grow better plants. Ignorance is bliss I guess...at least to some people.
FWIW, see the last resource I cited, there are a few reports about effects of light quality (i.e., spectrum).
There is no irony. What I wrote in the first post, e.g., that most LED lack sufficient green light, is not only a fact, but also not ironic to the thread title. What is ironic is you trying to claim I am not "doing" science correctly before you cite a paper, just like I have done, re: citing papers (albeit I have done so many times over).
green - best provided in diffuse form????
Well. I kinda thought you should do that yourself, since it's a study made by the same authors you use as argument for use of artificial green light. It took me 5 min. to find, should be second nature when you do science by other peoples studies, no matter what level you consider yourself to be.
Allways a good rule to check out the aúthors formore info, before you use their article as prove for your assumptions.
There is a lot of light articles going in another direction, you post whatever supports your opinion... IMO that is a problem if you want it to be scientific.
And BTW. I'm not for or against green LED's, since I admit I don't have the studies to prove it 100%. Just wanted to point out you also still have some ground to cover before you can say for sure.
I'll copy essential text and stay out of your forum from now on
-------
Abstract:
Measuring leaf light absorptance is central to many areas of plant biology including photosynthesis and energy balance. Absorptance is calculated from measured values of transmittance and reflectance, and most such measurements have used direct beam light. However, photosynthesis and other processes can differ under direct and diffuse light. Optical properties under diffuse light may be different, but there have been technical difficulties involved in measuring total reflectance of diffuse light. We developed instrumentation to measure this reflectance using a chopped measuring beam delivered alternately to sample and reference integrating spheres, and lock-in detection. We also built instrumentation for measuring transmittance of diffuse light. We developed standards to calibrate our instruments and correct for substitution error, a known systematic error with integrating sphere-based measurements. Helianthus annuus leaves measured under diffuse light reflected 5–10% more and transmitted a few percent less 400–700 nm light than under direct light. Overall absorptance was only a few percent higher under direct light, but leaves may utilize absorbed direct and diffuse light differently. For example, of the light entering the leaf, significantly more direct light than diffuse light is transmitted through the leaf, suggesting differences in localization of absorption within the leaf
Discussion
We have described instrumentation for measuring leaf transmittance and reflectance under both direct and diffuse light. Measurements of RDif were most challenging, but lock-in detection is extremely sensitive, and one can resolve a light signal from the leaf surface that is 0.05% of the background signal from the interior sphere wall. The close agreement of measured and theoretical RDif for fused silica and sapphire standards gave us confidence in the accuracy of our measurements.
This technique does not invalidate past measurements of leaf optical properties in any way; rather, it provides different information and can open new avenues of investigation. For example, some plant species photosynthesize better in direct light than in diffuse light (10); one possible explanation for this is that plants simply absorb more direct light than diffuse light, but of course there is no way to evaluate this possibility without the techniques described here. However, most laboratory and field measurements of photosynthesis are made using direct light, for which there is no need to resort to the more complex instrumentation described here.
An understanding of the optical properties of leaves under diffuse light is critical to our understanding of photosynthesis under diffuse light, and for applications such as remote sensing, but there have been few reports to date concerning reflectance, transmittance and absorptance of diffuse light. Brodersen and Vogelmann (13) reported that higher reflectance, lower transmittance and slightly lower absorptance were common under diffuse light, as we see here. Our report gives details on the instrument they used, verifies its accuracy and adds corrections for substitution error. For transmittance, these corrections are especially important at longer wavelengths—above 700 nm—where reflectance is high; for reflectance, they are especially important in the visible region of the spectrum where sample reflectance is low and much different from the reflectance standard. The earlier work reported only 400–700 nm, and their comparisons among leaves are valid, if not their absolute values of reflectance, transmittance and absorptance.
Interest in remote sensing has stimulated research seeking optical signals that might help identify major types of flora in an area from satellite images, and the directional quality of light could be a factor in interpreting such signals. Hume et al. (14) investigated whether monocots and dicots might be distinguished spectrally by measuring leaf optical properties under direct and diffuse irradiation at 350–2500 nm. They found no consistent difference in leaf optical properties between monocots and dicots under direct or under diffuse light, and they found no consistent difference in optical properties between direct and diffuse light in the visible region of the spectrum. Our instrumentation focuses on the visible and allows greater resolution such that we detect consistent differences in leaf T, R and A under direct and diffuse light. One major finding of Hume et al. (14) was that plants absorb significantly more diffuse than direct near-infrared (IR) radiation (725–1100 nm). We did not see increased absorptance of diffuse light over direct light between 725 and 800 nm, but our spectra do not extend to 1100 nm.
There are no known compounds common in healthy leaves that absorb in the near-IR, so absorptance in this spectral region is expected to be negligible. We found negligible absorptance of diffuse light from either adaxial or abaxial leaf surfaces. For direct light, however, we found negligible absorptance between 750 and 800 nm for light striking the adaxial surface, but 5–6% absorptance for light striking the abaxial surface. Some workers attribute apparent absorbance in the near-IR to a systematic error in the measurement of transmittance caused by incomplete collection of transmitted light when the sample is placed just outside the integrating sphere, at some finite distance from the integrating surface (15). If we had a systematic error in our measurements we would expect it to be apparent for both adaxial and abaxial surfaces. Further investigation will be required to determine the significance of this apparent absorptance.
The overall differences in absorptance of direct and diffuse visible light are small because increased reflectance under diffuse light is balanced by decreased transmittance. Nonetheless, the ability to determine these optical characteristics is important. For example, if observed differences in photosynthesis under direct and diffuse light (10) cannot be attributed to differences in absorptance, one must seek another explanation. Optical measurements are useful here as well; they suggest that although leaves absorb about the same amount of direct and diffuse light, they may utilize that light differently. Our data showed that of the light entering the leaf, significantly more direct light than diffuse light was transmitted through the leaf. This observation fits with previous work showing that the columnar palisade mesophyll cells can act as light guides, conducting light more deeply into the tissue, and that this light piping occurs more under direct than diffuse light (16). The difference between transmittance of direct and diffuse light depends on wavelength. The transmittance difference spectrum (direct minus diffuse) shows a peak in the green region of the spectrum (Fig. 4). If light is strongly absorbed, as red or blue is, little will be transmitted through the leaf irrespective of its directional quality. However, light that is less strongly absorbed, such as green light, can penetrate more deeply into the leaf (17) and is more likely to be transmitted out the other side. Light absorption profiles measured from chlorophyll fluorescence in the leaf suggest that direct light is absorbed more deeply in leaf tissue than diffuse light and that this difference is greater for green than for more strongly absorbed red or blue light (18). Thus, although absorptance may be only slightly higher in direct light than in diffuse light, the distribution of that absorbed light within the leaf may be very different. Distribution of light absorption within mesophyll tissues, not just total light absorption, is important because photosynthesis is optimum when the profile of light absorption across the leaf matches the profile of photosynthetic capacity (19).
Many leaves, especially thinner ones, show increased transmittance under high light as chloroplasts move from periclinal to anticlinal walls, opening windows for light transmittance to deeper cell layers (20,21). Changes in chloroplast position and the resultant transmittance changes are less dramatic under diffuse than direct light (3). The measurements reported here were made quickly, over minutes; although chloroplasts begin to move within minutes, those movements are often not complete for an hour or more. Thus, it is likely that for some leaves the differences in transmittance between direct and diffuse light that we report here might increase after longer, more intense irradiation sufficient to trigger chloroplast movement. One application of the technique we describe is to provide absorptance data, so photosynthesis can be expressed on an absorbed-photon basis; as photosynthesis measurements often take place over hours rather than minutes, chloroplasts would have time to move, and it would be important to consider these movements when measuring leaf absorptance.
The model we present showing how specular reflectance changes with degree of collimation suggests that light must be quite diffuse, spread over a cone of at least 60° from normal, before there is much change in specular reflectance. Our data for Helianthus suggest that the higher reflectance of diffuse light is mainly attributable to this increase in specular reflection, because the reflectance difference spectrum shows little indication of a chlorophyll signature, which would indicate diffuse reflectance from the leaf interior. According to our model, we might not have observed existing differences in reflectance if our diffuse measuring beam was less isotropic. Thus, the model indicates that to obtain realistic measurements of RDif, the measuring beam should be as isotropic as possible.
The model also has implications for future experimentation. For example, sunlight can vary from mostly collimated (with about 15% scattered sky light) to totally diffuse; it would be of interest to determine temporal patterns of how diffuse the light is in different environments so that it would be possible to estimate how often the light becomes sufficiently diffuse to cause changes in leaf specular reflectance. In addition, the degree of collimation of the ambient light will help determine when the relatively complex measurements of RDif and TDif are necessary. Unless the incident light used in the experiment is quite diffuse (>60° from normal), then the simpler measurements of RDir and TDir should be adequate.
The ability to measure optical properties of leaves under diffuse light extends our opportunities to explore a number of experimental avenues. Certainly, it is important for characterizing leaf absorptance so that one can express photosynthesis under diffuse light on an absorbed-photon basis. In addition, it will be possible to investigate leaf structure/optics relationships to determine what kinds of leaf structures or pigment arrangements might be correlated with differences in reflectance or transmittance under direct and diffuse light. Samples other than leaves are also of interest. For example, some flower petals have extremely papillate cells that may increase absorbance of diffuse light. Other organisms derive color not from pigmentation but from structural features that lead to interference or scattering, and it should now be possible to characterize their colors under diffuse light. Light in nature varies in degree of collimation, and we now have a routine method for characterizing optical properties of a variety of samples under light of varying directional quality.
I put white in parenthesis for a reason. Red and blue is what we know plants like using. Green is halfway between each.... therefore if you are saying that "white" light is just RGB then I understand you and your term.
I was asking if any light in addition to the already aforementioned USEFUL red and blue wavelengths fit the bill for "helping" photosynthesis, and if green was just one of many (any) kinds that would.
I meant for "less voluminous light" to mean light of lesser volume.
Yes, all light is best provided in diffuse form in terms of plants using the photons and photons more evenly irradiating the whole canopy.
It's your reference, so you should upload it. And don't try to lecture me on the value of reading full text papers, jeeze man, I have uploaded more full text papers than anyone else here at ICmag. And every real scientist "does science by other peoples studies"; stop trying to disparage something you know little about (re: the world of academia and science).
It appears you are being obtuse becuase I have proven you wrong, just knock it off will you? And I did not post any assumptions. This is my last post to you, if you can't understand that you are wrong, and why, then I can't help you.
I do not only seek what supports my position, I seek all info I can learn from. I don't start learning about something with strongly adhered to pre-conceived notions, I am happy to learn something I did not know; the same can't be said about you, apparently, from your disdain for green light info. See the paper about green light 'signal to slow down or stop' in my references; nuff' said.
I have no more ground I need to cover becuase this thread isn't about green light. This thread is on the topic of misconceptions about plants, of which, there are many. Did you even READ the links? Some LED lovers in this thread read the bit about green light and took it as an offense against their one true love: LED arrays.That said, in regards to green light, it's a fact green light is used for photosynthesis and other photo-reactions. That is the ONLY reason I wrote what I did in my first post about green light. And nothing you have written refutes what I wrote.
I'll copy essential text and stay out of your forum from now on
Just upload the damn study so everyone can read it; your copy and paste below lacks the 'Materials and Methods' section, which is important to read. This is not my forum, it is my thread though, so do as you like, I really couldn't care less.
BTW, nice find on that study, I have not read it before.
What you highlighted does not prove your claim that direct green light is better than diffuse green light, for photosynthesis. And besides, the topic of direct verses diffuse light is very off-topic to this thread becuase in both instances green light drives Pn and other photo-reactions.
What your reference is stating, is that diffuse light means reduced transmittance of photons through leaves. And that green light, when direct, has greater penetration into and transmittance through leaves, than blue and red. The same goes for diffuse green light verses diffuse red and blue; diffuse green light has greater transmittance than blue or red. That is something I and VG already wrote about in this thread.
Green light (either diffuse or direct) acts upon lower chloroplasts in leafs (i.e., is absorbed) to drive Pn to a greater degree. AFAIK that only happens once blue and/or red photons reach a point of absorption in the upper chloroplasts near saturation, which reduces the 'screening' (by movement of upper chloroplasts) of green photons. Thus allowing for greater absorption and usage of green photons by lower chloroplasts. See the first two papers I cited for more info on that phenomenon.
If the green photons were either direct or diffuse, the green photons would not act upon lower chloroplasts to drive Pn to the same degree as when blue and/or red photons reduced the 'screening' of green photons. This is not a diffuse verses direct light argument in terms of absorption of green photons for Pn, it's about blue and/or red light hindering (or not) green light from being absorbed and used for Pn by lower chloroplasts.
Diffuse green light is better than direct green light for a few reasons, and that is especially true in terms of more thorough irradiation of the whole canopy. The difference between direct and diffuse green light penetrating into lower leaf sections is not large once blue and/or red reduce screening of green; and under high irradiance, the difference is mitigated.
See this paragraph from your paper in regards to reduced 'screening' of (green) photons once blue and/or red photons affect upper chloroplasts:
Sounds good, thanks for explaining.
I am not sure what you mean by "helping". Green light drives Pn just like blue and red; green light doesn't "help" blue and red, per say. E.g., green light is not to blue and red light what "accessory pigments" are to chlorophyll.
I still don't follow. What do you mean by volume? Do you mean higher irradiance? Or do you mean percent of total PAR range light? Volume is not generally a descriptor for photons, so I am confused about what you mean.
So why are the presence of blue and red light necessary for green to "drive"?
Percentage. Looking at the sunlight spectrum I see a large VOLUME of green light.
This thread reminds me of the master defenses I used to go to in college. One person claims something, then it's nitpicked apart by all the other jaded botanists/scientists in the room, and then it just turns into an all out nerd fight with everyone trying to scramble and find as many other papers supporting their ideas over the other persons, all the while appearing effortless.
This thread is the epitome of Cannabis Botany and Advanced Growing Science.
This thread is the epitome of Cannabis Botany and Advanced Growing Science.
Thanks for the helpful addition molly 
They are not necessary for green light to spur photosynthesis. However, for green photons to provide the highest Pn they can (quantum efficiency), blue and/or red light is needed (i.e., high irradiance).
I would not consider blue and red light to be helpers for green light, more so they allow green light to reach its fullest potential in driving Pn. I know it sounds like I'm splitting hairs, but that's my understanding of the issues at hand. I can see why you may suggest blue and/or red light helps green light, I just don't think that's an accurate enough description of what is taking place...just my 2 cents.
I'm curious as to your hypothesis regarding an experiment involving solely green light being provided to a plant for the entire cycle with red being used very briefly to interrupt phytochrome production...
I would not do such an experiment, the result is not going to be better than providing the full PAR range; it will be worse. Just like provdiing only blue light, or only red light, providing only green light is not a good modus operandi.
Below is an interesting paper relevant to your question. The workers grew plants under only blue light, only green light, only red light, full sunlight, shaded sunlight and darkness; and then studied the effects on THC and CBC (and growth). It was found full sunlight, i.e., full PAR range light, was best, as should be expected IMO.
I do not recall if the workers in that study provided the same irradiance (PPFD and DLI; i.e., light quantity) in all light quality treatments; I think they did, but I am not sure. If they did not provide equal irradiance in all treatments that would affect the results to some degree.
"Effect of light quality on cannabinoid content of Cannabis sativa L. (Cannabaceae)"
Paul G. Mahlberg and John K. Hemphill
Bot. Gaz., vol. 144, no. 1, pp. 43-38 (1983)
- full text here: https://www.icmag.com/ic/showpost.php?p=4051526&postcount=44
How I wish there were photographs!!
I'm sure the green lighted plant was a leviathan.
I'm sure the green lighted plant was a leviathan.
S
sm0k4
Do you go by the lumen scale by any chance?
Nope, power output.
budlover123
Member
mean mr. mustard, I understand your skepticism, there are so many assholes talking about so much bullshit, mostly to sell, but these people are trying to have a legitimate conversation. Did somebody sell you a large heap of overpriced junk LEDs? If so I am truly sorry, but they are not entirely useless, and certainly green light isn't useless, and what do you base that volumetric heat storage thing on that just either doesn't make sense or is way over my head, can you dumb that down a little?
Spurrs,
This question: is green light needed by a plant? is really interesting but the discussion has definitely been more of a series of conjectures rather than a scientific look at what is going on in the plant. Plants in simple terms are using plant pigments to absorb light, produce electrons and thereby produce sugars using CO2. Photosythesis is of courrse a bit more complicated but you get the point no absorbance no energy and no photosythesis.
Here is a chart showing the absorbance spectra of a number of plant pigments including chlorophyll A and B.
OK now look at the region around 500nm, the green region of the spectrum. You will notice that both chlorophylls a and b are base line in their absorbance in this region. This means that photons of 475-525 nm do not excite the porpyrin ring electron cloud in chlorphylls a and b. Additionally the other accessory pigments also have low absorbance in the green region with a "well" forming in the combined spectra at about 500nm. In general if light is not absorbed it is reflected so you see why plants appear green in color? The @500 nm photons do not cause activation of chlorophyll in plants.
The acessory pigments however do abosorb some light in the geen specta and do contribute to photosythesis. This type of non-chlorophyll contribution really becomes important to marine plants that do not have acess to the high energy blue region of the spectrum which are scattered by water and thus developed a system to abosorb in the green and red regions of the spectrum.
The bottom line is; in nearly all land plants including cannabis chlorophyll is THE dominant photosythetic pigment and it just doesn't absorb green light...
Ok now to the question of green light driving photosythesis in plants... The answer is yes it does and it does so because of the carotinoid pigments contained in the chloroplasts along with chlorphyll.
Here is a grocery list of what is contained in the light sesitive structure of chloroplasts:
The structure of photosystem I in a cyanobacterium ("blue-green alga") has been completely worked out. It probably closely resembles that of plants as well.
It is a homotrimer with each subunit in the trimer containing:
* 12 different protein molecules bound to
* 96 molecules of chlorophyll a
o 2 molecules of the reaction center chlorophyll P700
o 4 accessory molecules closely associated with them
o 90 molecules that serve as antenna pigments
* 22 carotenoid molecules
* 4 lipid molecules
* 3 clusters of Fe4S4
* 2 phylloquinones
so about 4:1 chlorphyll a to carotenoid pigments which absorb strongly in the green region,**EDIT** I should also mention that the antenna pigments are also important in absorbtion in the green and yellow specturm and help the plant make use of the full spectrum of light. As we should expect from a creature which developed in the presence of full spectrum light.**
Green light is of relatively hi energy and can actually drive photosynthesis more effectively in plants than lower energy far red light simply due to more electrons promoted per photon which makes up for the lower number of photons absorbed. Also green light is able to penetrate plant tissue better than the higher energy short wavelength blue light and this adds to the absorbance by reaching chloroplasts deeper in the leaf.
Hope this sheds a little light on the discussion.
HM
This question: is green light needed by a plant? is really interesting but the discussion has definitely been more of a series of conjectures rather than a scientific look at what is going on in the plant. Plants in simple terms are using plant pigments to absorb light, produce electrons and thereby produce sugars using CO2. Photosythesis is of courrse a bit more complicated but you get the point no absorbance no energy and no photosythesis.
Here is a chart showing the absorbance spectra of a number of plant pigments including chlorophyll A and B.
OK now look at the region around 500nm, the green region of the spectrum. You will notice that both chlorophylls a and b are base line in their absorbance in this region. This means that photons of 475-525 nm do not excite the porpyrin ring electron cloud in chlorphylls a and b. Additionally the other accessory pigments also have low absorbance in the green region with a "well" forming in the combined spectra at about 500nm. In general if light is not absorbed it is reflected so you see why plants appear green in color? The @500 nm photons do not cause activation of chlorophyll in plants.
The acessory pigments however do abosorb some light in the geen specta and do contribute to photosythesis. This type of non-chlorophyll contribution really becomes important to marine plants that do not have acess to the high energy blue region of the spectrum which are scattered by water and thus developed a system to abosorb in the green and red regions of the spectrum.
The bottom line is; in nearly all land plants including cannabis chlorophyll is THE dominant photosythetic pigment and it just doesn't absorb green light...
Ok now to the question of green light driving photosythesis in plants... The answer is yes it does and it does so because of the carotinoid pigments contained in the chloroplasts along with chlorphyll.
Here is a grocery list of what is contained in the light sesitive structure of chloroplasts:
The structure of photosystem I in a cyanobacterium ("blue-green alga") has been completely worked out. It probably closely resembles that of plants as well.
It is a homotrimer with each subunit in the trimer containing:
* 12 different protein molecules bound to
* 96 molecules of chlorophyll a
o 2 molecules of the reaction center chlorophyll P700
o 4 accessory molecules closely associated with them
o 90 molecules that serve as antenna pigments
* 22 carotenoid molecules
* 4 lipid molecules
* 3 clusters of Fe4S4
* 2 phylloquinones
so about 4:1 chlorphyll a to carotenoid pigments which absorb strongly in the green region,**EDIT** I should also mention that the antenna pigments are also important in absorbtion in the green and yellow specturm and help the plant make use of the full spectrum of light. As we should expect from a creature which developed in the presence of full spectrum light.**
Green light is of relatively hi energy and can actually drive photosynthesis more effectively in plants than lower energy far red light simply due to more electrons promoted per photon which makes up for the lower number of photons absorbed. Also green light is able to penetrate plant tissue better than the higher energy short wavelength blue light and this adds to the absorbance by reaching chloroplasts deeper in the leaf.
Hope this sheds a little light on the discussion.
HM
Is green light needed? No. Is blue light needed? No. Is red light needed? No. Plants can grow under only blue light and under only red light, and under only green light too. Does a plant grow better when given the whole PAR range? Yes, for a few reasons, not only about Pn (e.g., quantum yield), but also about greater irradiance intracaonpy, etc.
The main 'negative' effects from green light can be reduced growth rate and reduced stomatal conductance if green light comprises too great a percent of the total PAR irradiance.
This thread is not based on conjecture, it's based on well proven science that plants use green light for photosynthesis, as well as other photo-reactions. The main reason I mentioned green light in the first post was to point out the myth that plants do not use green light for photosynthesis.
I have known about that figure for a long time, and the web-page whence it came has some incorrect claims about photosynthesis. That is a flawed figure to use, in terms of Chl A/B, I pointed this out in the first post. The Chl A/B absorption spectra does not accurately show what plants use (wavelengths) for photosynthesis via chloroplasts in vivo. That is the whole point of my first post, i.e., only using the Chl A/B absorption spectra is highly flawed. Also, in that figure there only only three cartonoids listed. That chart is a poor representation of what is going on in a leaf, in vivo.Plants in simple terms are using plant pigments to absorb light, produce electrons and thereby produce sugars using CO2. Photosythesis is of courrse a bit more complicated but you get the point no absorbance no energy and no photosythesis.
Here is a chart showing the absorbance spectra of a number of plant pigments including chlorophyll A and B.
OK now look at the region around 500nm, the green region of the spectrum. You will notice that both chlorophylls a and b are base line in their absorbance in this region. This means that photons of 475-525 nm do not excite the porpyrin ring electron cloud in chlorphylls a and b.
Accessory pigments do absorb green light (ex., some cartonoids), and there is only a slight dip in quantum yield (ex., K.McCree's Quantum Yield Curve) over green wavelengths compared to blue and red. The difference between quantum yield from blue to green to red is not large, read the work of K.McCree and many others for more info.
Only ~50-60% of green light is reflected, that is why we see leaves as being green; to assume nearly all green light is reflected is baseless.
It's a myth that there is a big difference between quantum yield of blue, green and red wavelengths in most higher terrestrial plants.
It's much better think about photosynthesis by chloroplasts than by chlorophyll:
"Chlorophyll alone is insufficient for plant photosynthesis. Many other enzymes and organic compounds are required. “Chloroplasts” is a better requirement." (cite)
FWIW, cannabis, like most higher terrestrial plants, are phytosystem I and II plants.
That has been covered in this thread ad nauseum. However, as noted in this thread, green light (photons) do not act upon lower chloroplasts until blue and/or red photons reduce the 'screening' effect of upper section of a leaf upon green photons (put simply).
Also, far red light (> 720 nm) has much reduced quantum yield compared to any wavelength in PAR range (400-700 nm). Granted, photons from ~380-720 nm drive photosynthesis, but far red light is > 720 nm. It has been found that green light can drive Pn (rate of photosynthesis) greater then both blue and red light, under high irradiance white light...far red light was never part of this thread.
Honestly it does not, at least to me. It seems you have fallen victim to the Chl A/B absorption spectra myth. What you wrote, the parts that are correct, have been covered in this thread already, except I didn't mention the energy of each photon at various wavelengths. I.e., blue light = more energy per photon (as much as twice that of red photons) but fewer photons per second at the same power as red light (power = energy/second); and red light = lower energy per photon but more photons per second. Green light has lower energy photons than blue but higher energy photons than red.
This thread was to make people aware of some myths believed to be facts in the cannabis world. Chief among them is the myth that plants do not use green light for photosynthesis and that all incident green photons are reflected. I do not see any reason to debate the merits of green light further, but, if you see a need feel free to post...
