I'm wondering where that chart came from. It is a basic truth, but far from complete. Different wavelengths within a light spectrum actually trigger different metabolic pathways. I studied this last semester. I'm pre-med majoring in Clinical Lab Sciences. Each chlorophyll has many molucules inside that need energy to work, energy in the form of different wavelengths of light depending on which molucule it is. Green light is not absorbed AT ALL but entirely reflected. That's why a green light will not interrupt the dark photoperiod. Wavelengths from 650 nm to 700 nm affect phytochromes, of which there are 5 known, and different plants have different numbers, cannabis has only two, Pr (phytochrome red) and Pfr (phytochrome infra-red). Yellow has little, but some effects on photosynthesis, the molecule if affects I'm not sure. What I am sure is there must be a balance of the lights spectrum. Henk, owner of Dutch Passion Seeds, tells us that a heavy blue spectrum during vegetative growth increases probability of female characteristics. But even a blue light has microamounts of the rest of the spectrum. If you tried blue LED, your plant will die because LED is wavelength specific and does not produce color outside it's specific spectrum. Pr responds to red light present and converts to Pfr. Pfr is, to my knowledge, completely inert and will not trigger hormones, but it does create a biological clock for the plant to know what season it is based on how long the light stays present. Once the light is gone, there is no red light to change Pr to Pfr and Pfr changes back to Pr triggered by infrared light, what we feel as heat, which is always present. Long days does not allow a critical amount of Pr to accumulate at night. I have heard some experts say that florigen is constantly produced, but that the long days do not allow for enough florigen buildup to actually see the results. Some experts say that phytochrome will only trigger the production of florigen with critical amounts of Pr after a long enough light period. I think the latter is more likely. It makes more biochemical sense when one understand metabolic pathways within living organisms.
For SkunkKushybrid:
The plant reflects nothing but green light. It absorbs all other light and in fact has the abillity to take in more than we can dish out. Little Big Way, winner of the 2005 Toker Bowl, grew an 8 foot Afghan Dream with a yield of 4 pounds. He used 4x 1000w Metal Halides on that one plant. We will not cause cell damage by a 5- 10 degree increase at night, especially if the daytime temperature is maintained at 65 or 70. Caretenoids do not respond to red light, but to Blue and Ultra Violet light (between 450nm to 500 nm). Some have debated the importance in UV light. Metal Halides have abundant amounts, but are weaker on the red spectrum. High Pressure Sodium is much stronger on the red spectrum, i.e. why it's a flowering favorite, but has no UV light. Ed Rosenthal sees little difference in yield between the two, but UV light has been proven to increase bud density, if not yield. For this reason, Jorge Cervante suggests a 2MH/1HPS ratio, or a 1/1 ratio for best results.
