Hosebomber
Active Member
You're right, maybe I should have said between 5 and 24% green.... I consider .6 grams (at 24%) of biomass over 60 days to be very little.
"Many previous studies indicate that even with blue light added to red LEDs, plant growth is still better under white light. Certainly to humans, plants grown under red plus blue light appear purplish gray, and disease and disorder become difficult to diagnose (Fig. 1). One possible solution is using a small amount of green light. To test this hypothesis, Kim et al. (2004a) grew lettuce plants under red and blue LEDs with and without 5% (6 μmol·m−2·s−1) green from LEDs with both treatments at the same total PPF (136 μmol·m−2·s−1). They observed no impact on lettuce growth with all measurable characteristics such as photosynthesis rate, shoot weight, leaf area, and leaf number being the same with and without green. They followed this work with another lettuce study to determine the effects of higher levels of green light under a total PPFof 150 μmol·m−2·s−1 and an 18-h photoperiod (Kim et al., 2004b). They used red and blue LEDs with and without green fluorescence (GF) (24% green for RGB or 0% green for RB), GF alone (86% green), and CWF (51% green) and demonstrated that lettuce plants grown with RGB had higher fresh and dry weights and greater leaf area than those grown with CWF or RB alone. Plants grown under GF had the least biomass of all treatments. Further work with the same system (Kim et al., 2004c) examined gS. Although lettuce grown under CWF showed greater maximal gS than under RB, RGB, or GF, dry mass accumulation was highest in the RGB treatment, indicating that gS did not limit carbon assimilation under the growth conditions provided. Additionally, the authors demonstrated that gS could be changed reversibly in response to narrow waveband light, even for plants grown under CWF (Kim et al., 2004c).Kim et al. (2006) summarized the experiments with green supplementation of red and blue LED light and concluded that light sources consisting of more than 50% green cause reductions in plant growth, whereas combinations including up to 24% green enhance growth for some species. For more information on plant responses to green light, see Folta and Maruhnich (2007)."
As for Heliospectra linking to that same tired ass study.... They have lost what little respect I had for them in their attempt to make a customizable controllable device. We have all read that study and know that we will never provide white light to the point of over saturation at which that deep leaf penetration with green photons will occur in a grow room. Every advocate of green lighting in LED panels will push that study (because it is the only one to ever make a claim that green light is better) every time they are questioned. I'm not saying that the use of whites to hit accessory pigments (of which some absorb in the green spectrum) isn't needed. I'm saying, after all these years I've been testing LEDs, you will never see me put a green discrete diode in one of my panels. It gives little to no return at the cost of a diode, the power it's drawing, and the space it is taking on my panel.
I'm running out of time atm and have to dig through studies, but I recall reading a few days ago that cannabis has a 4 quanta per CO2 @ 660nm. As for the action spectra stuff... absorption is what drives the action spectra and chlorophyll is not removed from the leaf to perform the action spectra, so there are other interactions occurring that are not directly involved with the absorption and action of photosynthesis that are being measured. Dr. Lee is doing some good work in this area.
As for HPS, (varies by manufacturer slightly) the initial peak is nearly always at 565nm (the very end of green start of yellow) and carries thru orange and red... never "mainly in green and yellow".
