Manipulating Short Day Length Flowering Using Narrow Band LED Lighting?

[Douglas.Curtis]

I've been wondering what the negatives could possibly be, regarding terpene production, yields and whatever. Every time I come across some mention of a new breakthrough, it usually comes with effects you don't necessarily want.

I really want to see a 24hr lighting chrysanthemum flower, just to compare it to the same flower under HPS or daylight. Just because. hehehe

 

[f-e]

My green leds gave up. I have already ordered more, but it will be another month till I get to try again. I'm just posting so you know it's happening. In a stainless kitchen pedal bin, which should make a nice reflector and a reasonable seal. Though it will be in a dark place to.

I have chosen 20w as some red&blue will still be radiated regardless. Unlike some, I believe 730nm is above 700nm and as such infra-red energy. Emitted by any warm item. I need to reduce the out of band radiation all I can, or this will be pointless.

I know from repeated experience, a plant turfed out a tent into a dark room will last about 5 days before obvious leaf clue's appear. That's with opening said tent daily. Lightening at the base of the leaf, like sulfur or iron, or cold nights into flower occurs. Which with half hours light a day, perhaps makes sense.

So, I have expectations and the kit almost to hand. Maybe I should do a separate thread and link to it here though. As it's already a few posts that may just be clutter here.

On a brighter note, I got a 20w green led on an 80mm2 heatsink, for under a fiver (though radio reception in the area will probably suffer)

 

[Douglas.Curtis]

It's amazing how much detail goes into even the most simple experiment. Yes, please start a new thread where you can document all this.

Photos help as well.

 

[Chunkypigs]

I saw an led lighting manufacturer somewhere with special far red lights that they claimed let you run 13-1/2 hours regular light, 1/2 hour far red then 10 hours dark.

They had what looked like solid info but not the numbers on intensity needed to make it work.

I just grabbed an assortment of some cheap leds for veg and I'm very impressed by the intensity of these dirt cheap industrial stadium fixtures and the shop lights. 500 watts panels for less than $100.
I figured I'd use them as designed outdoors in the yard if they failed at weed...

 

[Douglas.Curtis]

Interesting, so it seems this is not an isolated study and already being worked on. GREAT! I'm hoping it becomes a viable solution for long flowering sativas as well.

 

[Lost in a SOG]

5-15 minutes of far red after lights off.. tells them its night quicker..

The last light the sun gives out is far red and this switches the hormone phytochrome levels more towards pfr than pr which sets off morphological genetic changes, via an mrna messenger molecule (essentially the hypothesised hormone floragin). As the summer - autumn season draws on and the nights lengthen pfr dominance leads to faster and faster flowering, ie more hormones and genetic/morphological changes.

This can be used after flip to speed up flower onset which can cut a week off harvest and also as mentioned allow for longer days ,nearer 13.5 hours on, as the pfr is kept high enough for the plants to not be able to tell the difference.

Phytochrome: Pr and Pfr

Phytochrome*is a complex of pigments that occurs in 2 basic kinds:

one that responds to red light (Pr)

another that responds to far red light (Pfr)

Depending on the light frequencies that they absorb the most (even though the other frequency will also activate it and blue light too). The two pigments generally convert back and forth, with Pr converting to Pfr with red light and vice versa (although some forms of Pr/Pfr lose the ability to reconvert depending on the amount of light, the intensity, or the quality of the light received). The active form, which triggers responses such as flowering, is Pfr. Red light exerts the biggest influence on*photomorphogenesis(the effect of light on plant development) and far red light can sometimes reverse Pfr responses.

Phytochrome controls many functions such as:

gene expression and repression
gene transcription
the elongation of seedlings and stems
germination
photoperiodism (the flowering response)shade avoidance and adjustment to differing light levelschlorophyll synthesis.


Figure 3: The next morning, there is total light again and the ratio of pr to pfr returns to equilibrium.

One example of a red light response is the change in the light interval from long days to short days, which will trigger flowering in short-day plants. This is because the plant senses the change through the ratio difference between red light and far red (or no light), and begins to change its physiology from a state of vegetative growth to floral growth. While the plant is receiving light, the ratio of Pr to Pfr (Pr: Pfr) is approximately in equilibrium (in fact, Pfr is slightly higher). Pr is converted to Pfr by red light and Pfr is converted back to Pr by far red light. As the sun sets, the amount of far red light exceeds the amount of red light and the levels of Pr increase, resulting in a slightly higher concentration of Pfr and a lower concentration of Pr.

Pr is produced naturally by the plant during the darkness and accumulates. Pfr also slowly breaks down to Pr (its half-life is approximately 2.5 hours). The next morning, there is total light again and the ratio of Pr to Pfr returns to equilibrium. In this case, it could be said that Pfr is like the grains of sand in an hour glass. It is currently thought that when*Pfr concentrations are low and Pr is high, short-day plants flower and long-day plants do not. When*Pfr concentrations are higher and Pr concentrations are lower, long-day plants flower and short-day plants do not.

https://www.canna-uk.com/effect-of-red-and-far-red-light-on-flowering

 

[CrushnYuba]

I remember a couple years ago, there were some articals on far red being used to replace light deprivation. Never saw it in action. I seem to remember the theory was it started the plant on producing the hormones faster then with a regular dark period.
I'm super interested of anyone has tested it! This was years ago that i saw this arrival and then nothing.. So I'm not sure how promising it is

 

[Douglas.Curtis]

5-15 minutes of far red after lights off.. tells them its night quicker..

This does not work at the end of a 16hr lights on period. I understand the far-red effect, and it does have bearing on this. The subject is getting cannabis to flower under 18/6 lighting, through the manipulation of specific light wavelengths.

Can you provide every necessary spectrum for flowering but certain blues, and only run those spectrums 12hrs a day? In other words, which wavelengths of light does the plant pay attention to for triggering flowering? Is it possible to trigger flowering by only running those specific spectrums 12hrs a day, and the rest a full 16? Maybe even 18-20?

The ability to grow long flowering sativas, under 18-20hrs of light a day and still get decent flowers? Definitely something to work toward.

 

[Lost in a SOG]

They pay attention to the ratio between far red and red

From my understanding after about 14 and above hours the Phytochrome Far Red (PFR) will have started turning back into PR at levels that will out weigh the far reds effects on the plant. And the genetics will start to switch back into veg like morphology because they know its not winter.. perhaps adding extra FR in the middle of their night might work ?

Some people add extra far red in the day time to but to me it is slightly sub optimal though because it convinces the plant it is being shaded by other plants (that would filter out everything but the FR) so they stretch much more which we dont need in their day and they wouldnt get in nature on the middle of the day.. hence blue dominant bulbs giving shorter plants, you convince them they are all clear to be nice and squat and put more effort into rooting.

HPS lighting is generally higher in FR, due to the heat of the bulb, and this is probably why the growth is much stretchier under HPS.. and flowering comes on pretty quickly.

I cant think how you can do it unless sativas/cannabis, will put up with FR addition throughout to hold the R:FR in the right ratio to prevent revegging.. but they are already tall and adding the extra FR will make them go extra nuts stretch wise. The best use as i understand it is after dark to send to sleep quicker.

I suspect the various genetics will respond in different ways and the effects of poor spectrum may also have been why so many people used to get hermaphrodites but the incedence has decreased alot with better tailored lighting.. just a theory..

Some more phytochrome geek info.

Phytochrome responses:* Important plant responses regulated by the phytochrome system include photoperiodic*induction of flowering,*chloroplast development*(not including chlorophyll synthesis), leaf*senescenceand leaf*abscission.

Characteristics of phytochrome-mediated responses:

The*action spectrum*of the light needed for these responses shows a peak in the red at about 660 nm.These responses can be reversed by an application of far-red light (peak at 730 nm) soon after the red treatment.Sensitive spectrophotometers can measure a decrease in absorbance at 660 nm and in increase in absorbance at 730 nm when sensitive plant tissues are exposed to red (660 nm) light.The change in absorbance is caused by the conversion of a the photoreceptor from one structural form to another.* The red-absorbing form changes to the far-red absorbing form when it absorbs red light (660 nm) and back again when it absorb far-red light (730 nm).The phytochrome molecule is the photoreceptor for red light responses.* It exists in two forms, Pr and Pfr:

The Pr form:

Absorbs at a peak of 666 nmIs the form synthesized in dark-grown seedlings.When Pr absorbs red light, it is converted to the Pfr form.The Pfr form:Absorbs at a peak of 730 nmThe Pfr form is the active form that initiates biological responsesWhen Pfr absorbs far red light, it is converted to the Pr formPfr can also spontaneously revert to the Pr form in the dark over time = dark reversion; Pfr is also susceptible to proteinases.Pfr absorbs some red light, so in red light, there is a balance of 85% Pfr and 15% PrPr absorbs very little far red light, so in far red light, there is a balance of 97% Pr to 3% PfrPhytochrome is a family of proteins with a small covalently-bound pigment moleculehytochrome proteins occur as a dimer of two identical 124 kDa polypeptides, each with a covalently-attached pigment molecule.* Each polypeptide has three segments, or domains that have amino acid sequences similar to domains of other sensor proteins. [*reference*]
The pigment is called the chromophore.* It is a*linear tetrapyrrole.When the chromophore absorbs light, there is a slight change in its structure.* This causes a change in the conformation of the protein portion to the form that initiates a response.Phytochrome levels are much higher (about 50X) in dark-grown seedlings than in light-grown plants.* Its levels are highest near the apex of the plant.Molecular genetics has revealed the existence of*several genes*for this protein in a given plant.* All of these proteins use the same chromophore but differ in their sensitivity to light.The different phytochromes are involved in different biological responses to red light.Read more about the*phytochrome moleculePhytochrome allows plants to sense the color of light.Sunlight has a R:FR ratio of 1.2Light under a canopy of leaves has a R:FR ratio of 0.13Light under 5 mm of soil has a R:FR ratio of 0.88
*A higher proportion of FR light allows plants to detect when they are shaded.Plants adapted for growth in full sun will display greater stem elongation when they are transferred to shade.* They also develop smaller leaves and less branching.* This change is due to greater proportion of Pr to Pfr.
*Seeds of certain plants require red light for germination; FR light inhibits germination.* Many small seeds with low amounts of storage reserves (such as lettuce) show such a red light requirement.If these seeds they are buried below the level of light penetration in the soil, they do not germinate.If they are shaded by a leaf canopy, causing a high proportion of FR, germination is inhibited, Pfr is required for germination.Phytochrome and the Circadian Clock in Plants


"Photoreceptors and circadian clocks are universal mechanisms for sensing and responding to the light environment.* In addition to regulating daily activities, photoreceptors and circadian clocks are also involved in the seasonal regulation of processes such as flowering.* Circadian rhythms govern many plant processes, including movements of organs such as leaves and petals, stomata opening, stem elongation, sensitivity to light of floral induction, metabolic processes such as respiration and photosynthesis and expression of a large number of different genes." - drawing and quote from*Elaine Tobin's Website, UCLA.*

The Phytochrome Molecule

The structure of the linear tetrapyrrole is shown below.* It is attached to the phytochrome protein through a sulfur linkage.*
*

Phytochrome Genes and Proteins

There are five phytochrome genes in dicots, corresponding to the*Arabidopsis*genes termed phyA, phyB, phyC, phyD, phyE.* Monocots, like duckweeds, have fewer phytochrome genes, homologs of phyA, phyB, phyC. [*reference*]Phytochrome A*(PhyA), present only in angiosperms, is responsible for early events in germination and seedling de-etiolation. It is powerfully down-regulated in light both at the transcriptional and post-translational levels.* In darkness it accumulates to (comparatively) high levels.

Expression of the other phytochrome types (B to E in angiosperms) is independent of light and both Pr and Pfr forms are stable.

Phytochrome B*(PhyB) is probably the photoreceptor involved in shade detection and avoidance.* This response allows many species to greatly increase their stem extension rate when they become shaded by competitors.* The relative amount of Pfr*is reduced strongly by the presence of chlorophyll-bearing leaves that filter-out red light but not far-red.* The absolute irradiance is irrelevant. Through this red/far-red sensitivity, phytochrome provides the plant with a degree of color perception.* PhyB also is considered responsible for daylength detection in flowering and for tuberization in the potato, though the mechanisms are not understood.*Phytochrome C*(phyC) is a low-abundance member of the five-membered phytochrome family of photoreceptors in Arabidopsis.* Experimental data indicate that phyC may have some physiological roles that are different to those of phyA and phyB in the control of seedling responses to light signals.The Elusive Phytochrome "Receptor"

The mechanism by which the phytochrome (phy) photoreceptor familytransduces*informational light signals to photoresponsive genes is still unclear, although progress has been made.**

Phytochrome-GFP fusion proteins*migrate to the cell nucleus*after they are activated by red light.*
In the case of PhyB,*both photoactivation and nuclear translocation combined are necessary and sufficient for biological function.* Conversely, neither artificial nuclear translocation of non-photoactivated phyB nor artificial retention of photoactivated phyB in the cytosol provides detectable biological activity.

Several candidates for a phytochrom receptor are being investigated.* For example:

etc etc

https://www.mobot.org/jwcross/duckweed/phytochrome.htm

 

[Douglas.Curtis]

Very dense. Definitely related to the cause. lol