Hi, guys
I've been thinking about the flowering clones, too, and I think it must be a combination of things. I don't think it's solely the spectrum, as the other clones (from a different plant) in the bubbler show no signs of budding.
I do realize that 6500K is for vegetative growth and 2700K primarily for flowering, but when you think about it, we aren't really trying to veg clones; we're trying to root them. We don't really want to see a lot of new growth up top, as that is taking away the focus on root formation.
I looked for some information on light spectra and root growth, and there's not a whole lot out there. I don't know why 2700K was recommended to me other than the response of '2700K promotes root growth.' Sounded good to me!
I did some digging and here is what I came up with. I'm going to keep looking though.
Hold on to your hats, it's about to get nerdy in here.
Some foundational information from wiki:
Phototropism - growth of organisms in response to light
Some photosensitive receptors include phototropins, phytochromes and cryptochromes.
Phytochromes sense red light.
Cryptochromes and phototropins sense blue light.
"Stem tips exhibit positive phototropic reactions to blue light, while root tips exhibit negative phototropic reactions to blue light. Both root tips and most stem tips exhibit positive phototropism to red light."
(
Phototropism - Wikipedia, the free encyclopedia)
This is an abstract taken from the US National Library of Medicine/National Institute of Health, from a study titled "Light sources with different spectra affect root and mycorrhiza formation in Scots pine in vitro," which was a collaboration by three universities.
We studied the effects of broad-spectrum light quality on the interaction between the ectomycorrhizal fungus Pisolithus tinctorius (Pers.) Coker and Couch and Scots pine (Pinus sylvestris L.) seedlings and hypocotyl cuttings cultured in vitro. The light sources were cool white (CW), warm white (WW) and red-rich daylight (RD) fluorescent lamps. Inoculation with P. tinctorius enhanced adventitious root formation of the cuttings in all light treatments. Rooting of the inoculated cuttings was highest in WW light (89%), followed by CW (73%) and RD light (66%). During 6 weeks of in vitro culture, rooted cuttings formed only a few lateral roots. The fungus grew over lateral roots, but the Hartig net was absent in all light treatments. In non-inoculated cuttings, neither root formation nor subsequent root growth was affected by light quality. In the seedling experiment, inoculation in the WW treatment resulted in a significantly (P < 0.05) greater number of lateral roots than inoculation in the RD treatment. The percentage of lateral roots covered with fungal hyphae was also highest in WW light (62%), followed by CW (50%) and RD (27%) light. A similar pattern was observed in the intensity of Hartig net formation. We conclude that effects of broad-spectrum light quality on the ectomycorrhizal fungus-root interaction are dependent on the developmental stage of the root.
The abstract can be found here
Light sources with different spectra affect roo... [Tree Physiol. 2005] - PubMed - NCBI
The study in its entirety can be found here
https://treephys.oxfordjournals.org/content/25/1/123.full.pdf
I don't think this one study can prove or disprove anything, but it definitely makes want to find more information. I think I'm going to add another cool white bulb, just to be safe. Can't lose with a mixed spectrum, right?
Also, I just checked the bubble clones and all of them have roots now! (Even the flowering ones!
)
Wheeee!