Importance of 460nm red LEDs?
Quote:
Originally Posted by thepaan
For the whole grow. Flowering is accomplished by changing the length of the night (long nights induce flowering in most cannabis strains).
I understand this, but are you saying the oft-quoted "more blue for veg; more red for flowering" is not correct?
Seems you have the 'metal halide for veg and HPS for flower' meme, and the latest 'one light (CMH or properly designed LED) for the whole grow.
Now, I am not sure how much the solar spectra changes (filtered through the atmosphere) from spring to fall - if in fact we are somewhat attempting to
mimic nature.
Just lots of conflicting 'information' floating around that I am seriously trying to grok.
Thanks for all your scientific references! :thumbsup:
Importance of 460nm red LEDs?
"Now, I am not sure how much the solar spectra changes (filtered through the atmosphere) from spring to fall - if in fact we are somewhat attempting to
mimic nature."
Insolation changes very little at the equator and swings a bit wider from the tropics up to about 55 degrees latitude north or south. The only real change is the angle at which the sun hits our atmosphere which adjusts refraction and dispersion, and this happens due to Snell's law (going from vacuum of space to atmosphere) and our orbital position/axial tilt.
My panels are designed to emulate this effect in separate modules. Maybe another redesign will allow for adjustment to suit individual plant varieties but as far as general-purpose seasonal emulation goes I've probably got the best available.
Importance of 460nm red LEDs?
Quote:
are you saying the oft-quoted "more blue for veg; more red for flowering" is not correct?
More or less, yes.
As khyberkitsune said, the spectral content of light leaving the sun doesn't change; only the portion making it through the atmosphere does. I never considered if that would affect growth since I have never seen any studies along those lines. If I had to guess, I'd say it doesn't matter but honestly, I'm not sure.
Back to the question. I don't know why so many people think they need to change the color of the light, though I suppose it works since so many people do it. This is my guess: The cause of flowering (from light) clearly has nothing to do with blue wavelengths because phytochrome simply does not react to blue light. We are left with red light as the causal factor. Since cannabis is a short-day plant (flowering when the days become short or, long-night) and the day length is determined by duration of red light, then exclusive blue light (suggested for vegging) would cause the plant to reach the flowering stage more quickly due to a phytochrome-perceived perpetual night (is this the desired result?). But even MH should have enough red light to cause the day to be perceived and thus to postpone flowering. This is why I can't figure out why people say to use blue light. You can keep the plant from flowering by just leaving the lights on longer. The only advantage I can think of would be to give the plant more light but make it think it has a short day but that is not what they are doing.
Importance of 460nm red LEDs?
Quote:
Originally Posted by thepaan
More or less, yes.
As khyberkitsune said, the spectral content of light leaving the sun doesn't change; only the portion making it through the atmosphere does. I never considered if that would affect growth since I have never seen any studies along those lines. If I had to guess, I'd say it doesn't matter but honestly, I'm not sure.
Back to the question. I don't know why so many people think they need to change the color of the light, though I suppose it works since so many people do it. This is my guess: The cause of flowering (from light) clearly has nothing to do with blue wavelengths because phytochrome simply does not react to blue light. We are left with red light as the causal factor. Since cannabis is a short-day plant (flowering when the days become short or, long-night) and the day length is determined by duration of red light, then exclusive blue light (suggested for vegging) would cause the plant to reach the flowering stage more quickly due to a phytochrome-perceived perpetual night (is this the desired result?). But even MH should have enough red light to cause the day to be perceived and thus to postpone flowering. This is why I can't figure out why people say to use blue light. You can keep the plant from flowering by just leaving the lights on longer. The only advantage I can think of would be to give the plant more light but make it think it has a short day but that is not what they are doing.
The hormone that triggers flowering in cannabis has to build up - ANY light that triggers photosynthesis will destroy this hormone and interfere with the flowering process up until nearly the end of flowering (some clever people run their plants indoors for the first 6 weeks then finish them up outdoors in the summer sun because the hormone has built up so much that the plant cannot easily revert back into a vegetative stage.) Doesn't matter if it's blue light or red.
Importance of 460nm red LEDs?
wow, very technical thread !
thanks to you guys who know this stuff so the rest of us can learn :thumbsup:
Importance of 460nm red LEDs?
Ok so....
Ive read tons and tons since I started indoor growing. Ive always taken the blue light/mh/veg and red light/hps/flower comments as fact since ive read it so many places. Im now having problems finding the science behind that. I kept reading over what he was asking and I see where he is coming from. I looked at the charts on a page someone linked up above and it shows the peak absortion rates for Chloro A,B, and C. Like he said it shows the peak levels near the green and yellow. So why make these LEDs exact sectrums that are so low on the peak absortion chart?
Maybe im missing something....
Ive also read on some peoples logs that running MH or HPS the whole way makes no difference in their grows. I realize that people just typed out half a science textbook worth of info but I didnt see anywhere explaining why 400nm and 660nm are so important if they are so low on the absortion chart.
Importance of 460nm red LEDs?
Quote:
Originally Posted by GetThisOrDie
Ok so....
Ive read tons and tons since I started indoor growing. Ive always taken the blue light/mh/veg and red light/hps/flower comments as fact since ive read it so many places. Im now having problems finding the science behind that. I kept reading over what he was asking and I see where he is coming from. I looked at the charts on a page someone linked up above and it shows the peak absortion rates for Chloro A,B, and C. Like he said it shows the peak levels near the green and yellow. So why make these LEDs exact sectrums that are so low on the peak absortion chart?
Maybe im missing something....
Ive also read on some peoples logs that running MH or HPS the whole way makes no difference in their grows. I realize that people just typed out half a science textbook worth of info but I didnt see anywhere explaining why 400nm and 660nm are so important if they are so low on the absortion chart.
That absorption chart posted likely came from a study of Algae which have the extra side-structure that processes green light. In fact almost every one of those charts is derived from an algae study, as algae is inexpensive to produce and easy to create large quantities with a bare minimum of energy, this makes it a perfect sample test plant, but sadly, the results are useful only for under-water lighting.
Note you rarely see green plants underwater as often as you do above/on the surface of water - most seaweeds and kelps are brownish/yellow color, not green. They absorb more green, reflect more yellow and just barely use any of the sparse red/blue that manages to filter through the water.
Start taking terrestrial plants that are exposed to full sunlight, and that chart will almost universally reverse itself peak-wise.
Importance of 460nm red LEDs?
Whats up, Thepaan start some science threads. All your posts are really informative. I would rep you but I already did a while back. Seems like other people have. Every time you leave a post somewhere you get a new green dot.
Importance of 460nm red LEDs?
Thanks for the info! That would make sense... unfortunately I saw the graphs in some online cannabis grower book thing... let me try to find the link. Bahhhh..
Anyways that would make sense. So maybe the guy who started the post saw the same graphs I did??
Importance of 460nm red LEDs?
i haven't read through this whole thread yet, but i'll go ahead and give my $.02. chlorophyll a peaks both at 430nm AND just slightly less at 662nm. chlorophll b at 453nm and then slightly less at 652nm. LEDs usually only push two wavelengths, the two major ones for chlorophyll aborbtion, which push ATP and NADPH. white light runs the entire spectrum. there are other wavelengths that are needed by plants, such as beta carotene, phycoerythin and phycocyanin. plants need more than two wavelengths to complete all of their business....not that it can't be done by two, obviously.
part of the problem is that unscrupulous vendors jumped on the LED bandwagon and pushed inferior products with specific wavelengths (these emitters are cheaper than white) in a rush to get their products to market. while they do work, see Str8's log, but they aren't quite there yet. once the white emitters are more common and your plants can get the entire spectrum, LEDs will kick ass.
-shake
