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Thread: LED grow light users

  1. #17

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    UV is 320(uva)-370(uvb) nm

    When one is trying to replicate the sun using leds SMALL amounts of UV light are all that is necessary, yet still necessary to say you are replicating the Sun. Another thing one has to take into consideration is the spectrum of the Sun changes throughout the year.

    Looking at the peak PAR and response of pigments we have 4 types of main pigments we need to activate.
    Chlorophyll A
    Chlorophyll B
    B-carotene
    Xanthophyll

    They each correspond to certain spectrums of light and respond accordingly to more or less of that spectrum of light.

    The most responsive parts of the spectrum for chlorophyll A are 480nm and 510nm, pigment response is equal for both spectrums.

    The most responsive part of the spectrum for chlorophyll B is actually 440nm (80% responsive ) and 620-640nm (20% responsive)

    The most responsive part of the spectrum for B-carotene is 505nm , and a small spike <10% at 560nm

    The most responsive parts of the spectrum for xanthophyll are 400nm , 465nm , 515nm and 660nm all equally make xanthophyll respond.

    To "mimic" the Sun and use a spectrum that is comparable to the total year round spectrum of the , one would need an led for every type of chlorophyll wanted the plant to produce. A "full" spectrum led light should include 1 near UV led (370-400nm) , 1 blue at ~510nm , and 1 red at ~640

    This is because the biggest spike for b-carotene is at 505 and the 510 should be pretty helpful with that. If not a green led at 560 would guarantee that pigment being present. Under the leds it would look strange and colourful, but under normal light your plants will look vibrant and the colours of the plants themselves the reds and the greens will be very lush looking. You don't need more light in these spectrums, lots of light from your t5ho lights supplemented with smaller full spectrum led systems will make some for very fast growing plants. I personally plan to do this myself that's why I've done the research on it.

  2. #18

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    WOW! Thanks for sharing that info! Now that I know where to find it, I might consider putting together my own full-spectrum supplemental light panels for my plants. It's gems like this little post that make me want to stay involved in hobby forums.

  3. #19

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    No problem that's why I broke out my note book, feel free to double check any of my work. I have a friend building me a full spectrum led light to add the right spectrum into my light spread, my main light source is sunblaster t5ho lights right now but I still want to see first hand what this spectrum can do. I plan to do a side by side comparison between the full spectrum led lighting and just normal 6400k cool white fluorescent light bulbs

  4. #20

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    It is good to know the "absorption" spectra of accessory pigments on the antenna complex of the photosystems. But to me, the action spectrum of photosynthesis is more relevant. This is because in addition to the absorption, you'll need to know the ratio of the pigments and efficiency of the energy transfer from the accessory pigments to the reaction center (only the energy transferred to the reaction center P680 and P700 is relevant for the photosynthesis). So the action spectrum is more integrative efficiency of photons at different wavelength on photosynthesis (instead of just absorption). From this, one would conclude that using all red photons is most efficient. But there are issues with photomorphogenesis (e.g. you need to consider the effects of phytochrome, cryptochrome etc), so pure red doesn't do so well for most plants. In addition, there are interaction among wavelengths. The absorption and action spectra are measured under monochromatic light. So if you use more than one wave length, the photosynthetic output may not be the sum of the wave lengths. An example is that green light becomes effective once you start to saturate the plant with red light (this is fairly recent discovery).

    I'm sure that eventually people would make progress toward optimal grow light spectra (different for different species or different life cycle stages), but all I'm saying is that knowing the peaks of the absorption spectra is a good start, but it is just a part of it. Sorry for lecturing this, eithan, if you have know these issues already, but others who are not familiar with Plant physiology may start to think that the absorption spectra is the only important thing. In reality, it is much more complex (but this doesn't mean that hobbyists shouldn't experiment).

    Also, I'm pretty sure that imitating the spectra of the sun is not the goal. Remember the light environment where the precursor to the chloroplast evolved? It is different from the sun on the land.

    This may be an easy and interesting read for people interested in the topic:
    http://cpl.usu.edu/files/publication...b__2576523.pdf

  5. #21

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    Thank you for explaining why I picked the spectrums I did I have a little chat drawn up for each spike used.

    As stated all red would be nice and "works" but you are completely missing out on b-carotene which is used to harden the cells against uvb allowing for higher photo absorption , the lack there of would mean high intensity light sources would burn your plants thus it is a good idea to have a balanced spectrum even tho you can get away with using red spectrum lights like hps.

    I have a few notes on what each of the pigments does as well.

    Growth is alsi directed towards blue light. If you have a blue light on one side and a red on the other the plant will lean more towards the blue even if they are at the same photon intensity.

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