Phytochrome Questions

[grasshopper]

Pw

[GrowGreen]

Wasn

[suzy cremecheese]

The pigment phytochrome detects the presence or absence of light. This is how plants measure daylength.

When phytochrome absorbs red light with a wavelength of about 660 nanometers, the small protein that is attached to the phytochrome changes its folding. This changes some of its properties. For instance it becomes more hydrophobic and binds to membranes more easily when it is in the refolded state. Also it now absorbs light in the far red spectrum of 730 nm. When this form absorbs the far red light it refolds in its original form and the properties revert back to less hydrophobicity and it releases from any membranes it may of bound to.

Pr = red absorbing /660 nm
Pfr= far red absorbing/ 730 nm

Pfr reverts to Pr in darkness.

If far red light is given quickly enough after red light, phytochrome does not have enough time to affect cell metabolism and has no effect on the plant.

If the far red comes long enough after the red for the presentation time to be fulfilled, the Pfr is able to complete the transduction process and the far red light no longer cancels out the red light stimulation.

This is how critical night length is determined by the plant, the amount of time in darkness required to induce flowering. Cannabis is a long night plant therefore the night must be longer than the critical night length in order to induce flowering. In the case of cannabis the Pfr doesnt come for 12 hours (at least it dosnt in your closet) and now it no longer cancels out the red light stimulation and flowering is triggered.

[GrowGreen]

Suzy,

always a pleasure my friend..

I

[grasshopper]

..

[GrowGreen]

GH

I was more interested in everything above your filter. It think the magic is in the Florigen manipulation. Your plants coming off of a

[trichome pharm]

Phytochrome?
what is it?
whats it do?
what is so special about 660 nm?
what is so special about 730 nm?
whats a nm? :)
anyhoot
how about a thread about phytochrome?
and it's effects on plant growth?

all legit input is valued btw

fwiw

hmm
huhhh
ahhh
DOH!
nevermind !

[coffinman]

To put it simply, phytochrome acts like a switch, During the day the plant is flooded with red light, which changes more of the red light absorbing phytochrome (Pr) into the "switched on" far red absorbing phytochrome. This is what resets the internal clock of the plant.

During the night, molecules of phytochrome which are in the activated state (Pfr) slowly revert to the inactive form (Pr). The longer the period of darkness is the more molecules will become inactive thus triggering flowering.

[Papi]

Not to be confused with fidochrome, which is the new series of shiny metal dog dishes and collars sold by The Sharper Image.

[knna]

Dark reversion of Pfr to Pr is fast. In about 3h, 99% of Pfr has reverted to Pr. Plants have other mecanisms (still unkown) to measure dark period. When manipulating photoperiods by Pr/Pfr stimulation, its necessary to consider circadian rithms, wich interfere with results, depending of its duration.

Its is possible to cheat plants to believe that dark period has been longer than its real duration flashing with 730nm light at the end of light period, but in limited quantities, from 1/2 h to 2h, depending of plants species studied. I hadnt found any study about cannabis, so experimentation is needed to determine required intensity and duration of 730nm flash needed to shorten dark period requeriment to continue flowering, aswell to determine how much the dark period can be shorten.

I think its reasonable to expect about 8-9 h of dark period will be enough with flashing, up to maximun of 7h. But achieving a flowering photoperiod of 16/8 would be nice, because it allow to use lower light intensities (reaching the same total daily irradiance), with better photosyntetic efficiencies.

But phytocromes affect many plants behaviors, not only photoperiodic ones. Ph are probably the main signaling mecanism of plants, producing reaction in hormones, wich affect all the plant. The same experiment conducted with different species or the same but with different feeding likely can produce very different results.

Ive selected some pics to show how red/far red light ratio (and its correspondent phytocromes) affect plants.

First, a study with chrisantemun, wich show effect over morpholigical caracteristics and flowering time:
http://www.cannabis-world.org/cw/attachment.php?attachmentid=4513&stc=1&d=1155243101

Then results of an experiment with leds (the most appropiate for phytovromes manipulation due to its near monochromatic emission) in the Vilnius University. Its very interesting because it performs the experiment with 4 configurations of lighting, basically differenciated by the far red emission, and reports measurements of phytohormones and biometrics, and compare it with the control (HPS):

The first pic is the time schedule and light composition of experiment:
http://www.cannabis-world.org/cw/attachment.php?attachmentid=4514&stc=1&d=1155243101
And finally, biometric and phytohormones measurements:
http://www.cannabis-world.org/cw/attachment.php?attachmentid=4516&stc=1&d=1155243101
http://www.cannabis-world.org/cw/attachment.php?attachmentid=4515&stc=1&d=1155243101

knna

[GreenGrocer]

Papi,

Fidochrome...ROTFLMAO!!

GG

[Agent-Smith]

Do you think there could be a way to chemically cause this change? Or perhaps a "signal" of some sorts that could trigger it?

[grasshopper]

..

[knna]

ok
so i have a few questions
how long of flash?
ie 2 seconds per minute?/hour?
how strong of flash in footcandles?
duration of flash if it is a repeated type flash?


i read alot of sites
but few give any real details
so how many footcandles at 730 nm for how long? equals a flash?
how does one make a flash unit?
i read 15 hours somewhere as the timeline
that is for radishes
how about for canabis?

interesting stuff or sure

I wonder the same. Only experimentation can answer, and probably its strain dependent. I believe some strains require 10h of inunterrupted dark period to flower, but others need 11 and others 9. And of course, Rudelari's hybrids can be a PITA to know its dark requeriments, if exists.

But like a orientative point, work with the average 10h of dark period is a good reference.

From the literature, a 5min flashing can be enough if the light pulse have enough intensity. But ive seem studies with 30min pulses. Higher light intensities need lower pulse duration. Flashing can be continous lighting or pulsed (with higher intensity).

Like 730nm light have very low effect over human eye (although is still sensitive, very often is considered infrared), its neccesary to compute its intensity in mw/m2 rather than in fc or lux.

I believe that a irradiation of 2W /m2 during 30min must be enough to shorten the dark period up to 2h. The best moment of do it is at the end of the light period, as the less interference with circadian rythms.

There is two ways of build a 730nm emitter:

An incandescent light filtered or a 730nm LED emitter. Some leds that can ve valid:
ELD-720-524, 720 nm, 7 mW at 20 mA, 20

[grasshopper]

..

[GrowGreen]

I think the links were lost a few computers ago..

Google search Photoperiodism

Hydrorascal is a good source to find different spectrum LED.
A 730nm filter will not work, unless your looking for recessive hermi traits.:) At least for me it didn

[knna]

A good filter will work, but it block most of light, so a high intensity source is needed (halogens will be the best for this purpose), because you will obtain about a 2% of total wattage emited in the far red range.

You can check in http://www.ledtronics.com/. They have the LD200CWIR731-30D, about 2.5mW emitted at 20mA, 25 pcs cost 93$. The price per mW emitted is better in the Roithner's high power package.

GG, did you use the 730nm filter to experiment about shorten the dark period requeriment?

[knna]

Another table from "THE REACTION CONTROLLING FLORAL INITIATION", by H. A. BORTHWICK (1952), showing how a SD plant can reduce the dark period required to flower in more than 1,5h applying 30min of far red at the end of the light period. Applying red light lenghten the dark period requeriment.

PS: The light density used was 1,65 W /m2 (per second)

[grasshopper]

[w

[Carpet Muncher]

SWOOOOOOOSHHH....







the sound this thread made as it passed over head... :)

[knna]

Im spanish (from Spain:sun: )

[grasshopper]

..

[plantbuilder]

^ wonderful pdf
thanks

[suzy cremecheese]

Nine hours of darkness is all thats needed from my experience to trigger flower...but it kills your yield.
Any thoughts?

Yes, I think the more important number here is the maximum number of hours of dark that will still trigger flowering. It could be as much as 15 or more hours depending on the variety. If 12/12 yields more than 9/15 then wouldnt 15/9 yield more than 12/12?

I'm sure someone has tried this but I've never seen the thread on it...
Start flowering at 15 hours on, or whatever the critical day length is for your variety, and then shorten the day by 3 minutes a day until ripe. This might increase yields and hasten ripening.

Just a thought though. Do you have anything that might support or kill this hypothesis?

[knna]

Yes, I think the more important number here is the maximum number of hours of dark that will still trigger flowering. It could be as much as 15 or more hours depending on the variety. If 12/12 yields more than 9/15 then wouldnt 15/9 yield more than 12/12?

I'm sure someone has tried this but I've never seen the thread on it...
Start flowering at 15 hours on, or whatever the critical day length is for your variety, and then shorten the day by 3 minutes a day until ripe. This might increase yields and hasten ripening.

Just a thought though. Do you have anything that might support or kill this hypothesis?

Achieving flowering photoperiod with more light hours would be a great advantage:

-More total irradiation, or same total irradiation with lower light densities. Dry matter accumulation is basically related to total irradiation: more dayly irradiation, more dry weight.

In the other hand, photosintetic efficiency raise with light density until one point, the max efficiency point (in cannabis, between 25-45 klux, strain dependent). Further light density increases raise total grow, but at less rate, until the saturation point, where increases in light density dont report increases in yield. As the max eff point is reached with about less than 400watt of HPS per m2 (11 sq ft, aprox 35 watt/sq ft or less), wich is a lower density than often used, extend the light hours allows to low the light density to reach the same total irradiation, increasing the photosyntetic efficiency, thus, the gr/watt ratio (potential).

-Longer photoperiod's rates of light/dark correspond to more dry matter allocated in flowers and less in leaves. Carbon fixation partitioning is affected strongly by photoperiod.

But more important is the differenciated THC production. Not only more flower's dry matter accumulation, but more THC production. A controled experiment showed than THC production at 12/12 was double than at 10/14, and many times more than at 8/16. I havent found data with longer dayly photoperiods, but all suggest an increase in THC (more than proportional increase in dry weight)

-There is one disadvantage in longer photoperiod: reduction in Rubisco activity, reducing photosyntetic efficiency. This reduction is mainly correlationated with heat, so is theorically possible to avoid it, at less parcially. In the field, max reduction of Rubisco activity occurs at midday, with max light density. In controled chambers with constant irradiance, the decay in Rubisco activity occurs mainly after the nineth hour of light. But a dark pause can restore Rubisco activity to higher levels.

knna

[grasshopper]

"w

[grasshopper]

"w

[plantbuilder]

http://64.233.167.104/search?q=cache:9njgig2wrMwJ:www.overgrow.com/edge/showthread/t-236220.html+far-red+light+in+cannabis&hl=en&gl=ca&ct=clnk&cd=3
http://www.public.iastate.edu/~bot.512/lectures/phases.htm
http://www.mobot.org/jwcross/duckweed/phytochrome.htm
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Photoperiodism.html#mechanism
http://www.nature.com/nature/journal/v419/n6904/abs/nature00996.html
http://www.publish.csiro.au/paper/PP9740445.htm
http://www.publish.csiro.au/paper/PP9760207.htm
http://blogs.warwick.ac.uk/nathanbarrow/tag/infrared
http://www.pubmedcentral.gov/articlerender.fcgi?artid=365931
http://www.pubmedcentral.gov/articlerender.fcgi?artid=1086493
http://fins.actwin.com/aquatic-plants/month.9603/msg00398.html
http://fins.actwin.com/aquatic-plants/month.9611/msg00337.html
http://www.weedfarmer.com/cannabis/thc_guide.php
http://search.usda.gov/search?q=phytochrome&btnG=Go%21&filter=0&as_sitesearch=ars.usda.gov&ie=&output=xml_no_dtd&client=usda&lr=&proxystylesheet=ARS&oe=
http://search.usda.gov/search?q=phytochrome+pfr&output=xml_no_dtd&sort=date%3AD%3AL%3Ad1&ie=UTF-8&lr=&as_sitesearch=ars.usda.gov&client=usda&filter=0&oe=&proxystylesheet=ARS
http://www.sciencedaily.com/releases/1999/10/991012075916.htm
http://www.blackwell-synergy.com/doi/pdf/10.1046/j.1365-3040.2002.00840.x#search=%22guelph%20phytochrome%2 0flowering%20red%22

after reading all that crap
i am leaning toward loading far-red light in the am
peace
pb

[GrowGreen]

Some tips:

Run the Hermi Cannon for two hours after the Lights go out. This cuts two hours off your night time.

Cannabis really only needs 10 hours of darkness to release florigen. So the cannon will drop you down to 8

Using a 8hr night and 16hr day period-
If you start the far-red from the beginning of flower, it will add two weeks to your normal stretch time.

I don

[knna]

About the problems inducing flowering with far red, what i do is use a 6/12 photoperiod during the first week (more indicas, up to 2 week for more sativas), reducing stretching and shortening the transition period.

Although i havent start the far red experiments yet, from what ive read i deduce that a strong far red component during the first one or two days is the reccomended. I suggest to use the far red treatment only in the first 2 days, and let the 6/12 do the rest. When finish the 6/12, continue with the far red treatment with the 16/8.

The flowering induction have two phases in SD plants: first, the induction itself, where giberelins content raise quickly (promoted by far red), and then the differenciation of future flowering nodes. This second phase is dominated by the raising in auxins content, so here the far red treatment can be counter productive.

If you want to use the far red treatment from the beggining, maybe adding auxins after the third day is an option.

knna

[grasshopper]

[w

[grasshopper]

aw

[knna]

More fun!

From "Signs of the time: enviromental input to circadian clock" (http://jxb.oxfordjournals.org/cgi/content/full/53/374/1535).

"The circadian clock forms one of the most fascinating adaptations to life on earth. Organisms can not only anticipate the day/night cycle but can make use of an internal clock to measure daylength as an indicator of the changing of the seasons. The innate period of the clock is not exactly equal to 24 h, but is reset each day by environmental signals at dawn and dusk, most notably by changes in light and temperature. This ability to re-entrain also ensures that the clock is synchronized with the day/night cycle which in turn is crucial for anticipation of dawn and dusk. Recent advances in the field have identified the photoreceptors involved in resetting the clock in several systems. This has revealed surprising similarities, but also key differences in the circadian systems of plants, fungi, insects, and mammals. One recurring feature emerging from this research is that the photoreceptors themselves are under the control of the clock with transcript abundance being tightly regulated. Furthermore, elements of a feedback pathway whereby the clock modulates the activity of the light input pathway are now being identified.
(...)
The circadian clock does not run in isolation from the cycle of day and night. It must, itself, be set to the correct time. The clock must include a resetting mechanism by which it can first be synchronized with the day/night cycle so that the organism can correctly anticipate dawn and dusk. This clock resetting is a phenomenon very familiar to any travellers on long-haul flights. When a person travels through several time-zones, initially jet-lag is experienced whereby his/her circadian clock remains set to the timing of dawn and dusk in the place of departure though, gradually, over the course of a few days he/she finds his/her rhythm of sleep and wake has adjusted to the new timing of dawn and dusk.

The two most prevalent environmental cues which act as Zeitgebers (time givers) are the changes in light and temperature occurring at dawn and dusk and both are capable of resetting the clock (Edmunds, 1988; Roenneberg and Foster, 1997). The circadian clock can be thought of in terms of three major components: an

[knna]

This article : "Photoreceptors and Regulation of Flowering time" (http://www.plantphysiol.org/cgi/content/full/123/1/39) rewiews the genetic flowering pathway and how each photoreceptor works. Very complete, although its mayority refered to arabidopsis, a facultative LD plant.

[plantbuilder]

great links knna!

http://www.plantphysiol.org/content/vol123/issue1/images/medium/pp0506017001.gif