Grow Lights Australia
Well-Known Member
Haha! I'm not entering into that argument!Maybe I need to look more? As in quickly Google for studies? (Your snark aside, I do appreciate the effort.)
That second link you provided shows precisely why this subject needs far, far more study before growers or light manufacturers start making definitive claims. Though they state (and fairly so) that their addition of far red resulted in increased dry fruit mass, they also happen to cite one study which found an increase which was "not statistically significant", and yet another study which showed that additional far red actually decreased the dry fruit mass. So I remain unconvinced.
I'm very happy that you, GLA, Amare, and all the other experimenters out there are trying these different ratios and working toward more real-world data, but... It's early days for claims, in my opinion.
I did have a look through the studies posted above and I have read others including the Italian study @ChiefRunningPhist posted up, which both @Prawn Connery and I have also linked to in the past. So I know there is at least some information out there, though admittedly there is not a lot of info that is cannabis specific due to its illegal status for so long. Thankfully that is changing. Unfortunately it is still illegal in most parts of Australia, so we can't conduct our own experiments. But we can at least observe results in other countries, like the Or_Gro test at the heart of this thread.
Most of those studies focus on the ratio of red to far red, so in some ways in may not be the amount of red itself that has the biggest influence on flowering yields, but on the ratios. We do know that red is responsible for regulating fruiting and flowering in short-day plants, and that is what those (and other) studies prove.
I'll state right now that I am not a botanist, so if I get anything wrong then I will happily defer to anyone who has greater knowledge! But I have done a bit of reading on the subject.
One thing that surprised me was Einstein's theory of light that proves photosynthesis is directly related to photon absorption and not spectral energy. This doesn't seem to make sense at first because a blue light photon contains more energy than a red light photon so it's easy to assume that blue light would elicit a greater response in plants than red light, but that is not the case. Einstein's universal law states that one photon is required to elevate one electron to a higher state regardless of how that photon is created. I'm not about to argue with Einstein!
So if all photons are equal, but blue photons require more energy than red photons, then obviously red photons are a more efficient driver of photosynthesis. I am talking purely about photons vs photons, as we know that chloroplasts absorb different spectra based on their pigments and some spectra are absorbed more efficiently than others (most green light is reflected, for example, even though it is also a very efficient driver of photosynthesis due to how far it penetrates the leaf cell structure and how many chloroplasts it activates).
Einstein's theory, in combination with the spectral absorption curve (McCree), explains why red light is such an efficient driver of photosynthesis. Because it has a very high quantum efficiency. So if red light is the most efficient driver of photosynthesis then it must also be the most efficient driver of any photomorphogenic response that relies on photosynthesis – and that would include flowering.
The point of all this is that if red light improves overall yields compared to other light, then it MUST improve flowering yields. You can't have fruit or flowers without leaves, stems, branches and roots! So anything that increases the efficiency of plant growth must also increase its efficiency to make fruit and flowers by default.
I hope that makes sense.
I think we can all agree there are many studies showing the effect of greater amounts of red light, in combination with blue, on plant growth and how it increases leaf size and mass, and stem and petiole elongation. There should be no reason why those same effects are not observed in fruiting and flowering, and at least one of the studies above (tomato yields) shows that.
The other point I wanted to mention is that there are five pigments that absorb light in plants but only two of those pigments - Pr (phytochrome red) and Pfr (phytochrome far red) – are responsible for regulating fruiting and flowering. They are also the only pigments that absorb red light! In addition, blue light has been show to inhibit flowering in short-day plants such as cannabis. At least according to this research: https://gpnmag.com/article/effects-of-blue-light-on-plants/
Another study (below) goes into the effects of red and far red light with specific reference to cannabis (except that most of the sources cited do not reference cannabis!) This article references a number of studies showing that red light accelerates flowering, and that the ratio of red to far red light increases biomass and shortens flowering times. Here it is: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6455078/#ref126
All this proves is that plants simply cannot produce optimum fruiting and flowering yields (if at all) without red light. Extrapolate this further, and it becomes obvious that increasing levels of red light must improve fruiting and flowering yields – just as it has been proven to increase leaf and other biomass. There may be a point at which too much red light inhibits flowering, but from a Zero red-light base you would expect increasing levels of red light to increase fruiting and flowering yields up to that point.
So perhaps the reason there are not so many studies into flowering yields under red light is that the answer is obvious. Or maybe it's just that plant scientist who already know this are more interested in the relationship between red and far red light. Really, I don't know why.