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03-14-2010, 01:37 PM #11Junior Member
Calling out to Weezard for LED advice
I checked with NASA records to check the insolation levels recorded at the edge of the atmosphere... I noticed... blue was in the lead... So
I figured a 60:40 blue:red mix for vegetationAre you growing space-weed? What does the solar radiation at the edge ofthe atmosphere have to do with anything? I don't think the relative intensities of different wavelengths of sunlight have anything to do with it either. As green and yellow are also more dominant wavelengths than red your logic suggests you should add lots of those to your LED array. Let me know how that works out.I'm very confused as to how you managed to infer what you just stated from my post.
http://www.emc.maricopa.edu/faculty/...BK/pigment.gif - something from an educational facility. http://3.bp.blogspot.com/_pFQ0wrHWd1...pectrum_en.jpg - there's another.
Counterpoint: I present this document. I realize it isn't an actual study but I can't find a copy of the one they cite as the source of the data. http://envsupport.licor.com/docs/TechNote126.pdf Figure 1a shows leaf absorption spectra. Compare to your second absorption image and to the absorption spectra on page 4 of this study The Photosynthetic Action Spectrum of the Bean Plant -- Balegh and Biddulph 46 (1): 1 -- PLANT PHYSIOLOGY and notice how 6 different species of plants represented on page 6 (labeled page 375) in this study Absorption Spectra of Leaves. I. The Visible Spectrum -- Moss and Loomis 27 (2): 370 -- PLANT PHYSIOLOGY. Furthermore, in that last study, notice how on page 10 and beyond they show that as you destroy the leaf the absorption characteristics change to show the absorption of the base components - such that the absorption begins to look more and more like your first image the more desiccated the leaves become. I cannot make this clear enough; absorption is not a measure of response.
Figure 1b shows action relative to incident energy. Remember, different wavelengths of light have different energy? When you weight the amount of photosynthesis that occurs (measured from the amount of oxygen produced) by the energy of each wavelength you get something that shows how low-energy waves (670-680 nm) elicit a greater response than the high energy waves of 450 nm. Compare to page 3 of this study Photosynthetic Action Spectra of Trees: I. Comparative Photosynthetic Action Spectra of One Deciduous and Four Coniferous Tree Species as Related to Photorespiration and Pigment Complements -- Clark and Lister 55 (2): 401 -- PLANT PHYSIOLOGY showing the relative rate of photosynthesis of 5 different trees. Notice how all 5 of them produce oxygen at a high rate in the red but somewhere between a lowered rate and a negative rate in the blue. That's correct: a negative rate. The Blue Spruce actually stops photosynthesizing and begins photorespiration under exclusive blue light instead of photosynthesis.
Figure 1c shows action relative to quantum absorbed. "Quantum" in this case is the number of light particles absorbed (light is both a particle and a wave). Higher-energy wavelengths need fewer particles to have the same intensity. The higher-energy 450 nm light gets an advantage in this one and yet, it is still only 70-80% as efficient as 640 nm light. Compare again to the action spectra on page 4 of this study The Photosynthetic Action Spectrum of the Bean Plant -- Balegh and Biddulph 46 (1): 1 -- PLANT PHYSIOLOGY.
What we gather from all this is first, all plants have a similar response to all wavelengths. Second, this response is maximal in the red - specifically red peaks which correspond to chlorophyll a and b. When measuring by energy, which is what the output of LEDs is given in, (as opposed to quanta) of light, blue is only half as efficient as red. From this we can deduce that the most efficient way to cause a plant to produce oxygen, which is the measure of the rate of photosynthesis or the rate of response, is by exposure to red light corresponding to the red peaks of chlorophyll.
Depends on the plant being studied - not every plant responds the same - every species has vastly different requirements. For example Tradescantia pallida actually thrives under yellow and green light, which is why it does so well on the forest floor and in well-shaded areas. If you have the materials to conduct a colorimetric analysis, you will see that against a blackbody emitter, a tube filled with chlorophyll actually allows more red light to pass through than blue light. Actually, you can do this with a light bulb and a test tube full of centrifuged chlorophyll - put the light next to your head, hold tube in front of your face - the tube appears to be filled with green fluid. Put the tube between your face and the light, you see mostly red.
Red is required for photomorphogenesis, root development, and for vegetative growth. Blue is for control of certain day-night reactions, seasonal identification, and most importantly, for actual plant growth and bulk. This is why CMH and MH are the recommended primary HID light source by large commercial-scale horticultural operations, and not HPS.
Those NASA-conducted studies are old, and they recanted half of them, their new panel design has 33% blue, 67% red.
That again depends on the species of plant - The phytochrome can also respond to the ratio of red versus blue and the intensity of both wavelengths in order to determine seasonal changes.No, it will not eventually flower without regard to light color or duration unless you're growing a Ruderalis. How do you think we keep mother plants for decades?
It appears cannabis is either a short day obligate, short day facultative, or day-neutral. So, you may be correct in some cases but the point is flowering related to light exposure is caused by the length of the dark period and not the ratio of blue to red. In the case of non-obligate strains it will eventually flower on its own regardless of light quality.
Chapter 1, page 3 : here Marijuana Botany: Propagation and ... - Google Books "Cannabis flowers when exposed to a critical day length which varies with the strain. Most strains have an absolute requirement and less than this will result in the formation of unformed flowers only." (obligate) published in 1981.
Cannabis sativa is a SDP facultative http://www.lhup.edu/smarvel/biol206/...phogenesis.doc
Wikipedia lists cannabis as short-day facultative but take that with a grain of salt....
More on plant flowering: floinduc
I think you have the misconception. I do this across the globe and don't get paid to be wrong. If I was wrong and selling a bad product, I'd have been sued already.
I knew I should have saved that picture or site link
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