justlooking
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The claim that green light does not drive photosynthesis is totally false and a myth. The usage of the "chlorophyll A/B absorption spectra" is not correct in terms of what drives photosynthesis. The chlorophyll A/B absorption spectra was found in vitro with a spectrophotometer using an extract of a leaf, not a real leaf and not in the real world, i.e., ex vivo. If you look at the "Action Spectra of Photosynthesis" from Keith McCree circa 1975 (or the work of Katsumi Inada, circa 1970-1980) you will find that in fact, green light drives photosynthesis more than blue light, I have written about his countless times. And not only that, but it has been fond that green light drives photosynthesis better than red light too under high irradiance white light (white light is a mix of b/g/r)! That is because green light will transmits into the canopy and reflects into the canopy via "sunfleck" and then gets bounced around from leaf to leaf until it's absorbed or reflected away, thus green light has much more leaf surface area for absorption. Blue light and red light get absorbed mostly in the very upper canopy while far-red light penetrates into the canopy more than red light via transmittance. Green light penetrates into the canopy via transmittance and sunfleck. Green light offers the best penetration into the canopy to light lower buds and leafs.
The other reason the chlorophyll A/B absorption spectra is false (if used to model the best light for photosynthesis) is because there are many chlorophyll "accessory pigments" (ex. "carotenoids") which absorb light other than blue and red and then transfer the energy for photosynthesis. This is fact, plain and simple. If you do not believe me than please call up Licor and ask them if green light is used for photosynthesis, or ask any plant physiologist or plant scientist. And please read the work of K.McCree.
Here are some papers and graphics which prove my point:
In the graph below, Action Spectra of Photosynthesis, we can see that blue light produces less photosynthesis per photon than does red light, however, note that green light should have a higher peak than blue and red light for most plants when grown under high irradiance white light (see first and third references below by I.Terashima, et al., and by A.Tanaka, et al., respectively ). White light would be any any light system that emits non-monochromatic (non-single color) light, such as LEDGirls arrays which emit white light. White light is a mix a b/g/r, thus any LED array with blue, white and red diodes is a white light, the same is true if it's a mix of blue, green and red diodes. The reason I mention the flaw in the Action Spectra of Photosynthesis is that K.McCree used monochromatic LED light to measure each bandwidths' effect upon rate of photosynthesis when making his graph, the Action Spectra of Photosynthesis, he did not use white light or study how white light will effect the Action Spectra of Photosynthesis. In reality when we all use a mix of b/g/r light instead of monochromatic light and it has been born out that green light is a better driver of photosynthesis under white light, this is *important* because no one uses monochromatic (I.e., single color) light to grow cannabis.
Monochromatic light was a rather poor method for K.McCree and K.Inada to use considering no one uses monochromatic light (i.e., single color light) to grow plants, all LED arrays use a mix of blue/red or blue/green/red or blue/white/red diodes. Thus the Action Spectra of Photosynthesis *NOT* the "chlorophyll a/b absorption spectra" is what should be used when looking at SPDs with the understanding that green light should have a higher peak than blue and/or red under high irradiance. This also means most LED arrays are sorely lacking in the light that best drives photosynthesis and best irradiates the lower canopy.
In terms of rate of photosynthesis the levels of blue/green/red are less important than is the overall irradiance, that is, as long as there are sufficient amounts of each light type, there should be about 40% green light for cannabis type plants, 40% red light and 20% blue light. Please see the work of Alexander A. Tikhomirov in the references below for info on the topic of the mix of blue/green/red. In cannabis type plants the leafs supply most of the assimilate (e.g., from light) into the bud it is attached to via petiole and branch, just like cucumbers as cited by A. Tikhomirov. Cannabis has buds all over the plant, bottom and top, where again, the leaf closest to the bud supplies most of the light assimilate into the bud. Not only that, but the buds themselves photosynthesize, that fact is little realized by cannabis growers, but it is a fact none the less. Thus we can see why it's *VERY* important to have a lot of green light to irradiate the lower canopy and hence the lower buds will get bigger, less "popcorn" buds. Not only that, but the whole plant photosynthesis also depends upon lower leaf irradiance, as well as upper leaf irradiance.
In the graph below the "quantum response" is what unweighted PPFD looks like, it is what a quantum sensor measures, for example the Licor Li-190. . To weight PPFD to create the lamps' "Quantum Flux Density" we would use the "Average Plant Response" in the figure which is really the Action Spectra of Photosynthesis, however, as I wrote, we should realize that green light plays a bigger role than is shown in the Action Spectra of Photosynthesis.
Reference:
That figure of McCee's ASP is from this Bruce Bugbee paper:
"EFFECTS OF RADIATION QUALITY, INTENSITY, AND DURATION ON PHOTOSYNTHESIS AND GROWTH"
by Bruce Bugbee
International Lighting in Controlled Environments Works
http://ncr101.montana.edu/Light1994Conf/1_5_Bugbee/Bugbee text.htm
Here is the average "quantum response" of the Li-cor Li-190 quantum sensor that LEDGirl is using:
Lastly, as I have shown countless times with four different peer-reviewed journal articles each finding the same results, the ideal PPFD for cannabis to reach the highest yield, growth rate and rate of photosynthesis is 1,500. However, considering the "Daily Light Integral" (i.e., the total irradiance over the whole day) is what can cause photoinhibition (ex. light bleaching of leafs) more so than PPFD under 1,600 it seems wise to lower PPFD to ~1,300 so the Daily Light Integral will be lower while the rate of photosynthesis (and hence yield and growth) stays very high. I for one think using a benchmark of 1,000 PPFD as the lowest irradiance to use for high rate of photosynthesis (and hence yield and growth) during veg and flower is *VERY* wise. I try to offer ~1,300 PPFD all day long...
Other references:
1. "Green Light Drives Leaf Photosynthesis More Efficiently than Red Light in Strong White Light: Revisiting the Enigmatic Question of Why Leaves are Green"
by Ichiro Terashima, Takashi Fujita, Takeshi Inoue, Wah Soon Chowand Riichi Oguchi
Plant and Cell Physiology 2009 50(4):684-697
http://pcp.oxfordjournals.org/cgi/content/short/50/4/684
2. "Why are higher plants green? Evolution of the higher plant photosynthetic pigment complement"
by J.N. Nishio
Plant, Cell and Enviromment (2000) 23, 539-548
http://www.oxygraphics.co.uk/whygreen.pdf
3. "Photosynthetic Research in Plant Science"
by Ayumi Tanaka and Amane Makino
Plant Cell Physiol. 2009 April; 50(4): 681–683.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2669890/
4. "SPECTRAL COMPOSITION OF LIGHT AND GROWING OF PLANTS IN CONTROLLED ENVIRONMENTS"
by Alexander A. Tikhomirov
International Lighting in Controlled Environments Works
T.W.Tibbitts (editor) 1994 NASA-CP-95-3309
http://ncr101.montana.edu/Light1994Conf/1_3_Tikhomirov/Tikhomirov text.htm
5. Action spectra for photosynthesis in higher plants.
by Katsumi Inada
Plant and Cell Physiology, 1976, Vol. 17, No. 2 355-365
http://pcp.oxfordjournals.org/cgi/content/abstract/19/6/1007
6. McCree, K.J. 1972. The action spectrum, absorptance and quantum yield of photosynthesis in crop plants. Agric.Meteorol. 9 : 191-216.
7. McCree, K.J. 1972. Test of current definitions of photosynthetically active radiation against actual leaf photosynthesis data. Agric. Meteorol. 10 : 443-453.
The other reason the chlorophyll A/B absorption spectra is false (if used to model the best light for photosynthesis) is because there are many chlorophyll "accessory pigments" (ex. "carotenoids") which absorb light other than blue and red and then transfer the energy for photosynthesis. This is fact, plain and simple. If you do not believe me than please call up Licor and ask them if green light is used for photosynthesis, or ask any plant physiologist or plant scientist. And please read the work of K.McCree.
Here are some papers and graphics which prove my point:
In the graph below, Action Spectra of Photosynthesis, we can see that blue light produces less photosynthesis per photon than does red light, however, note that green light should have a higher peak than blue and red light for most plants when grown under high irradiance white light (see first and third references below by I.Terashima, et al., and by A.Tanaka, et al., respectively ). White light would be any any light system that emits non-monochromatic (non-single color) light, such as LEDGirls arrays which emit white light. White light is a mix a b/g/r, thus any LED array with blue, white and red diodes is a white light, the same is true if it's a mix of blue, green and red diodes. The reason I mention the flaw in the Action Spectra of Photosynthesis is that K.McCree used monochromatic LED light to measure each bandwidths' effect upon rate of photosynthesis when making his graph, the Action Spectra of Photosynthesis, he did not use white light or study how white light will effect the Action Spectra of Photosynthesis. In reality when we all use a mix of b/g/r light instead of monochromatic light and it has been born out that green light is a better driver of photosynthesis under white light, this is *important* because no one uses monochromatic (I.e., single color) light to grow cannabis.
Monochromatic light was a rather poor method for K.McCree and K.Inada to use considering no one uses monochromatic light (i.e., single color light) to grow plants, all LED arrays use a mix of blue/red or blue/green/red or blue/white/red diodes. Thus the Action Spectra of Photosynthesis *NOT* the "chlorophyll a/b absorption spectra" is what should be used when looking at SPDs with the understanding that green light should have a higher peak than blue and/or red under high irradiance. This also means most LED arrays are sorely lacking in the light that best drives photosynthesis and best irradiates the lower canopy.
In terms of rate of photosynthesis the levels of blue/green/red are less important than is the overall irradiance, that is, as long as there are sufficient amounts of each light type, there should be about 40% green light for cannabis type plants, 40% red light and 20% blue light. Please see the work of Alexander A. Tikhomirov in the references below for info on the topic of the mix of blue/green/red. In cannabis type plants the leafs supply most of the assimilate (e.g., from light) into the bud it is attached to via petiole and branch, just like cucumbers as cited by A. Tikhomirov. Cannabis has buds all over the plant, bottom and top, where again, the leaf closest to the bud supplies most of the light assimilate into the bud. Not only that, but the buds themselves photosynthesize, that fact is little realized by cannabis growers, but it is a fact none the less. Thus we can see why it's *VERY* important to have a lot of green light to irradiate the lower canopy and hence the lower buds will get bigger, less "popcorn" buds. Not only that, but the whole plant photosynthesis also depends upon lower leaf irradiance, as well as upper leaf irradiance.
In the graph below the "quantum response" is what unweighted PPFD looks like, it is what a quantum sensor measures, for example the Licor Li-190. . To weight PPFD to create the lamps' "Quantum Flux Density" we would use the "Average Plant Response" in the figure which is really the Action Spectra of Photosynthesis, however, as I wrote, we should realize that green light plays a bigger role than is shown in the Action Spectra of Photosynthesis.
Reference:
That figure of McCee's ASP is from this Bruce Bugbee paper:
"EFFECTS OF RADIATION QUALITY, INTENSITY, AND DURATION ON PHOTOSYNTHESIS AND GROWTH"
by Bruce Bugbee
International Lighting in Controlled Environments Works
http://ncr101.montana.edu/Light1994Conf/1_5_Bugbee/Bugbee text.htm
Here is the average "quantum response" of the Li-cor Li-190 quantum sensor that LEDGirl is using:
Lastly, as I have shown countless times with four different peer-reviewed journal articles each finding the same results, the ideal PPFD for cannabis to reach the highest yield, growth rate and rate of photosynthesis is 1,500. However, considering the "Daily Light Integral" (i.e., the total irradiance over the whole day) is what can cause photoinhibition (ex. light bleaching of leafs) more so than PPFD under 1,600 it seems wise to lower PPFD to ~1,300 so the Daily Light Integral will be lower while the rate of photosynthesis (and hence yield and growth) stays very high. I for one think using a benchmark of 1,000 PPFD as the lowest irradiance to use for high rate of photosynthesis (and hence yield and growth) during veg and flower is *VERY* wise. I try to offer ~1,300 PPFD all day long...
Other references:
1. "Green Light Drives Leaf Photosynthesis More Efficiently than Red Light in Strong White Light: Revisiting the Enigmatic Question of Why Leaves are Green"
by Ichiro Terashima, Takashi Fujita, Takeshi Inoue, Wah Soon Chowand Riichi Oguchi
Plant and Cell Physiology 2009 50(4):684-697
http://pcp.oxfordjournals.org/cgi/content/short/50/4/684
2. "Why are higher plants green? Evolution of the higher plant photosynthetic pigment complement"
by J.N. Nishio
Plant, Cell and Enviromment (2000) 23, 539-548
http://www.oxygraphics.co.uk/whygreen.pdf
3. "Photosynthetic Research in Plant Science"
by Ayumi Tanaka and Amane Makino
Plant Cell Physiol. 2009 April; 50(4): 681–683.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2669890/
4. "SPECTRAL COMPOSITION OF LIGHT AND GROWING OF PLANTS IN CONTROLLED ENVIRONMENTS"
by Alexander A. Tikhomirov
International Lighting in Controlled Environments Works
T.W.Tibbitts (editor) 1994 NASA-CP-95-3309
http://ncr101.montana.edu/Light1994Conf/1_3_Tikhomirov/Tikhomirov text.htm
5. Action spectra for photosynthesis in higher plants.
by Katsumi Inada
Plant and Cell Physiology, 1976, Vol. 17, No. 2 355-365
http://pcp.oxfordjournals.org/cgi/content/abstract/19/6/1007
6. McCree, K.J. 1972. The action spectrum, absorptance and quantum yield of photosynthesis in crop plants. Agric.Meteorol. 9 : 191-216.
7. McCree, K.J. 1972. Test of current definitions of photosynthetically active radiation against actual leaf photosynthesis data. Agric. Meteorol. 10 : 443-453.
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