Inkbird Digital Display ITC- 608T

[cbdhemp808]

They are pigments... phytochrome red (Pr) and phytochrome far red (Pfr). They function as a seesaw: either they are in balance, or one outweighs the other...

Red-headed Hobbit on the left is Pfr, outweighing his friend red-coated Pr, and exclaiming "hooray, no flowering yet!". Hobbit in the center is sad because he has to wait for the pipe weed to come around. Notice the lighting in the background... Pr is kept "up" because of bright light.

"Pr absorbs red light between 660 and 760 nm and Pfr absorbs far red light between 760 and 800 nm."

During the dark period (scotoperiod), Pr naturally builds up (Pfr is converted to Pr). After several nights in a row of this, flowering phase will be initiated. However, one flash of light during the scotoperiod that contains the red wavelength (660nm) will cause the Pr to be converted back into Pfr, all at once, and will prevent or reverse flowering.

It is the sufficient presence of Pfr that keeps the plants from flowering. When cannabis is grown outdoors under natural light conditions, Pr builds up (and Pfr diminishes) when the nights get long enough, typically about 10.5 hours of darkness for most photoperiod cannabis strains.

 

[bluter]

I've heard that for decades and it struck me as strange because I was taught in grammar school (high school in NA) that it was the green colored chlorophyll in the chloroplasts that caused us to perceive leaves as green. That was some time ago but, from what I can determine, it is still correct.

In terms of plants being able to use green light for photosynthesis, there's a good body of evidence to support that assertion.

Green light is included in the spectrum of emissions in the 400-700nm range labelled "photosynthetically active radiation" ("PAR") . I've taken it on faith that's because the radiation falling in that range is photosynthetically active.

The McCree curve was the initial research into what became PAR. Images of the curve are ubiquitous, one example is here:

Snarfed from - https://www.researchgate.net/profil...umens-as-represented-by-their-comparative.png

The Y axis label, "Relative Photosynthetic Efficiency" indicates that green photons are photosynthetically active.

The Wikipedia, the source of all true knowledge (Photosynthetically active radiation - Wikipedia) discusses the part that green photons play in photosynthesis. The graphic below is from that discussion:

On the Wiki page, these are the titles of the papers in the first two footnotes:

"Green Light Drives Leaf Photosynthesis More Efficiently than Red Light in Strong White Light: Revisiting the Enigmatic Question of Why Leaves are Green"

Green Light Drives Leaf Photosynthesis More Efficiently than Red Light in Strong White Light: Revisiting the Enigmatic Question of Why Leaves are Green

"Green Light Drives CO Fixation Deep within Leaves"

http://pcp.oxfordjournals.org/content/39/10/1020.full.pdf+html

Per Bugbee, showing the deep penetration of green light into the leaf where it penetrates the "leaf all the way to the bottom. It lights up the spongy mesophyll. It's terrific for its…"

Source unknown. Deals with absorption of photons and demonstrates the absorption of photons in plant leaves, plant species is unknown.

Interesting mention of green working synergistically, reminiscent (to me) of the synergy between deep red and far red, perhaps.

Blue Radiation Interacts with Green Radiation to Influence Growth and Predominantly Controls Quality Attributes of Lettuce | CEA Talk

u.osu.edu

i see it's in relation to a spectrum component in white light, not as a singular element powering plant growth alone, which may be the difference in how green light in the grow is used.

as far as the chloroplasts, the colours of everything we perceive are what is reflected back at us, not just plant material.

it can't be a massive part, as for years we grew plants under burple led with absolutely no green in the spectrum whatsoever. white light is definitely more complete and carries the green with it, plants under it respond better than burple alone. would point to another reason the white light led revolution has proven so successful supplanting hid and burple.

 

[Delps8]

i see it's in relation to a spectrum component in white light, not as a singular element powering plant growth alone, which may be the difference in how green light in the grow is used.

as far as the chloroplasts, the colours of everything we perceive are what is reflected back at us, not just plant material.

it can't be a massive part, as for years we grew plants under burple led with absolutely no green in the spectrum whatsoever. white light is definitely more complete and carries the green with it, plants under it respond better than burple alone. would point to another reason the white light led revolution has proven so successful supplanting hid and burple.

Yup, did the blurple for my grow in 2017. Big change when I started growing again in 2021. Out with the blurple. in with the Mars SP 3000. Big difference, in all respects, especially because of the almost 400% increase in output.

Per the graphic in the Wiki article, I think efficiency for green was about 20% which is lower the others but still an appreciable contribution.

White LED + far red is big - the far red + deep red create a synergy that results in better yield than just the extra photons. Bugbee discusses this in his vid with Migro Shane that they dropped about three weeks ago.

The basic rule that Bugbee pushes is that light quality (spectrum) shapes the plant whereas light quantity drives yield. That's from, say, four years ago until very recently because, in the interim, the deep red + far red synergy has gone from theory to being demonstrable.

 

[Delps8]

They are pigments... phytochrome red (Pr) and phytochrome far red (Pfr). They function as a seesaw: either they are in balance, or one outweighs the other...

Red-headed Hobbit on the left is Pfr, outweighing his friend red-coated Pr, and exclaiming "hooray, no flowering yet!". Hobbit in the center is sad because he has to wait for the pipe weed to come around. Notice the lighting in the background... Pr is kept "up" because of bright light.

"Pr absorbs red light between 660 and 760 nm and Pfr absorbs far red light between 760 and 800 nm."

During the dark period (scotoperiod), Pr naturally builds up (Pfr is converted to Pr). After several nights in a row of this, flowering phase will be initiated. However, one flash of light during the scotoperiod that contains the red wavelength (660nm) will cause the Pr to be converted back into Pfr, all at once, and will prevent or reverse flowering.

It is the sufficient presence of Pfr that keeps the plants from flowering. When cannabis is grown outdoors under natural light conditions, Pr builds up (and Pfr diminishes) when the nights get long enough, typically about 10.5 hours of darkness for most photoperiod cannabis strains.

That's excellent! Thank you for providing the detail.

That will be stored in is a PDF in my "Lighting" folder.

 

[cbdhemp808]

The plant evolved on this light (solar) something like 28 to 34 million years ago...