I need help with Red to far red light ratios with LED lights

Discussion in 'Indoor Growing' started by kennyray6269, Mar 24, 2011.


    kennyray6269 Member

    I have been doing a lot of research on LED grow lights, and I think i know why a lot of them do not work. Most of them do not use far red at all, and most of them have one set ratio of blue to red. From what i have read during the vegetation stage the red to blue should be 2 to 1 and during flowering the red to blue ratio should be 6 to 1. I have read about experiments using filters to filter out far red out of natural sunlight. The experiments concluded the plants under the filter were shorter and stockier, and the ones which were not filtered were taller, but both plants had the same amount of flowers. This could be very good for growing marijuana. But, it is my understanding that plants need far red light to flower and bud. I have red that far red light induces flowering. I have been doing research to try and figure out a way to build a better LED grow light. I have figured most of it out except the far red. I have read Marijuana plants also us UV light for resin production. I am thinking of using some 6500k white light to help with this. The LED light i have designed is 48 inches long and 26 inches wide it has 12 rows of lights space 2 inches apart. The lights are all 1W. 16 white 6500k, 72 blue 470nm, 30 orange 612nm, 42 red 630nm, 72 red 660nm and 40 far red 730nm. During the vegetation stage, and through the first week of flowering, I will shut off the 40 far red lights, making a 2 to 1 red and orange to blue ratio. For the rest of the flowering stage I will shut off 42 of the blue lights and turn on 40 far red lights making a red and orange to blue ratio of 6 to 1. Does anyone know anything about red and far red ratio? Is my light ratio correct? Or should i not even use the far red lights at all?

    anymouse Active Member

    You're on the right track, I can tell you'll do better with LEDs than most.
    I'm currently assembling my LED stealth box retrofit so I have little experience growing with LEDs (15w bloomboss spot to test the waters) however I can give advice based off of what I scraped from across the internet these past 2 years. Take it with some salt of course. Most of what I have is coming from too many sources to cite but you'll find the applicable information if you google around enough (It's best to get information first hand from research papers anyhow) and ignore what the companies that sell grow lights say. They are marketing people, not botanists.

    You should be good with your blue/red ratios. Red can be less specific of a frequency than blue however both can vary widely from the "optimum" frequency and still maintain good performance. Focus first on which LED will provide a higher luminous flux and then on what is closer to optimum, especially in red.
    As long as you keep within the peak range of 450-475nm for blue and 575-675nm for red. [​IMG]LEDs in that frequency range are common and cheaper/more efficient than trying to get an exact frequency. Trying to get the absolute perfect frequency is like losing a race because you spent the first hour mixing your fuel at the starting line for an extra 5% speed boost.

    I'm sure you know that more than just two frequencies are important for the xanthophyll and carotenoids however your 6 white LEDs should be plenty to cover that and I concur with your color temperature choice.

    I went with CREE XPE LEDs for the red-orange and blue and CREE XPG for white in my box. Those I found after a couple months of on and off research to be the best balance of energy efficiency, PAR, and cost.

    As far as your far red I feel you're planning on using waay more than you actually need. I've seen people help flower their outdoor plants by "spraying" their plant with near infrared by just shining it across all the leaves for a couple of seconds each day with a handheld light. You only actually need just a few and can fill the rest of the light with whatever cheaper red you're using.

    You should click here and check out this experimental grow going on in Amsterdam. He used only 2 far red I believe and that greatly shortened his flowering time. His name (or at least what he goes by) is Hans and he has been doing grow after grow and making frequency, diode, amperage, cooling, etc. adjustments to his grow panels and has since out performed conventional HPS for yield per watt hour. I don't agree with his non-scientific approach; it lacks control groups and the information is poorly organised. His findings and methods do however match up with what information I've found across the internet to be true and he is getting real results, not just theory and hearsay like you find anywhere else. He also believes all of the store bought LED lights are worthless though I have much harsher words for them(and those bastards almost had me believing LEDs are a gimmick that will never be useful for growing). Read his results from beginning to end to get the whole picture.

    UV, ah the Underestimated Violet. If you try to implement UVB into your grow without undue cost I'd say go for it. The current theories are that UVB either converts CBD into THC (Lydon and Teramura 1987) , UVB damages the plants cells and in response it creates more resin (THC absorbs UV), or that plants which evolved in high UV climates have higher resin content in much the same way humans have melanin (Pate 1983). Nobody seems to have anything but anecdotal evidence and theory that it actually works but most signs point to yes. I'm going to put a repti glo CFL in my box and have an external switch to cut the power and prevent accidental exposure. I strongly advise you to do the same if you do try this.

    I've been taking pictures as I'm upgrading my box and I'll probably post them on RIU if you're interested in seeing how it works out for me. Just PM me so I remember to tell you when I do.
    Carmelo Angel

    Carmelo Angel Member

    Hey kennyray6269, I think you really shoud use Far-Red light, because RED AND FAR-RED LIGHT ARE SYNERGISTIC. This interaction is called the "Emerson Enhancement Effect". Emerson, a scientist, tried combining wavelengths and observed that red light (680 nm) could drive a certain amount of photosynthesis; far-red light (700 nm) could drive a similar amount. When the two colors of light were combined, the amount of photosynthesis yield was greater than the sum of the individual color yields. He concluded that there must be two different photosystems involved in photosynthesis, one driven by short-wavelenth light and one driven by long-wavelength (PS1 and PS2). Both photosystems are needed to both oxidize water and to reduce NADP+. They work together to enhance efficiency and convert the light energy to forms that can be absorbed by the plant. For this reason, you should have far-red light in both the vegetation stage and the flowering stage. What I don't really know is the ratio.

    As you probably know, there are light receptors color pigments in the leaves called Phytochrome Red (Pr) and Phytochrome Far Red (Pfr). These pigments get their names from the types of light they absorb. Pr absorbs red light between 660 and 760 nm and Pfr absorbs far red light between 760 and 800 nm. These two pigments chemically react to the light, and trigger the plant to flower or not. In cannabis plants, the normal presence of Pfr switches off the flowering signal. Is here where I want to make my point. You have some ways to control the levels of Pfr:

    -- Phytochrome is a chromoprotein whose state is influenced by light. It is mainly produced in darkness and exists first of all as PR.
    -- When Pr absorbs red light, it is converted to the Pfr form.
    -- When Pfr absorbs far red light, it is converted to the Pr form
    -- Pfr can also spontaneously revert to the Pr form in the dark over time = dark reversion; Pfr is also susceptible to proteinases
    -- Pfr absorbs some red light, so in red light, there is a balance of 85% Pfr and 15% Pr-- Pr absorbs very little far red light, so in far red light, there is a balance of 97% Pr to 3% PfrSo..

    To induce flowering to your lovely plants, you can manipulate the photoperiod and control the amound of red and far-red light.You can simply change your light cycle to 12/12, but your plants will take two weeks to stard flowering, because Pfr switches back to Pr during darkness, Pr levels gradually increase and the Pfr gradually decrease during the dark period. Now that you know the effects of far-red light in Pfr, you can induce flowering faster by increasing the levels of Pr and decresing the levels of Pfr. And also, it would be fun to find out if you can even harvest marijuana outdoor in the middle of june, just by placing LEDs of far-red light next to the plant, even during night, decreasing the levels of Pfr enough. Maybe it can not be done but certainly, you could get an early harvest.

    md2of2 Member

    In my wonderings I came across this.

    "You are right about PS1 and PS2 but u forgot to mention as why the red drop actually occurs.. well i think that red light is of high wavelength (647- 700 nm ), and blue light has a frequency of (422- 492 nm).. therefore when we incident red light on a plant its PS1 gets activated (as it is activated by wavelengths of 700 nm ) and thus giving rise to cyclic photo phosphorylation on the other hand if we give the plant a light of alternate frequencies at the same time( red and blue light alternatively ) then the plant receives a wavelength of 680 nm (approx) thus activating both PS1 and PS2 and thus leading to non-cyclic photo phosphorylation...thus a better photosynthesis"

    So could we say that plants are more efficient at absorbing the 680nm wavelength with the addition of blue light than without it? Any idea of what amount or ratio of blue light is required to activate the PS2 systems. Also where does the far red spectrum fit in as I thought this was the focus in the EEE, that it was the need for the far red to trigger the PS2. Also someone here mentioned pulsing FR and R on lettuce seeds to stop or allow them to germinate. I'm really trying to understand the whole FR thing.

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