How plants tell time

LEDBud

Well-Known Member
Having sound knowledge allows us to make decisions that can be built upon with success , this thread is dedicated to learning and sharing real life experiences.

This first article is base knowledge but relevant for those adjusting light schedules in a common or uncommon manner
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How plants tell time

Plants of the same species tend to flower, fruit and go to seed with remarkable synchronicity. How are they able to keep such rigid schedules?

Gardeners often marvel at how plants of the same species tend to flower, fruit and go to seed with remarkable synchronicity, as if on cue. Some flowers even follow a strict daily routine, opening their petals at dawn’s light and closing at dusk. How are plants able to keep such rigid schedules? The secret lies in a kind of vegetative internal clock that has fascinated CALS plant scientists for decades. Here’s what they’ve learned about how it works:

See the light. The primary component of plants’ internal clock is a light-absorbing molecule known as phytochrome. A turquoise-colored pigment that can exist in two different forms, phytochrome inter-converts between a “Pr” form, which absorbs red light, and a “Pfr” form, which absorbs far-red light.

The sun winds the clock. In full sunlight, plants’ leaf cells contain equal amounts of phytochrome’s two forms—50 percent Pr and 50 percent Pfr.

The clock counts down at night. When it’s dark, phytochrome molecules that are in the Pfr form start converting to Pr at a slow, steady rate. Because this rate is constant, the amount of Pfr remaining in the leaf cells at any given time is a direct reflection of the number of hours a plant has sat in darkness. In this way, plants use phytochrome to count the hours of the night—they don’t directly measure day length—and use that information to dictate when they sprout, flower, fruit and go to seed during the growing season.

Plants got rhythm. The phytochrome clock enables plants to establish a 24-hour circadian rhythm. For plants that open their flower petals at dawn and close them at dusk, the phytochrome clock allows them to anticipate the sun’s rise and set. In fact, when placed in a dark closet, these plants will continue to open and close their flowers right on schedule for a number of days, until the circadian rhythm finally dampens.



What plants do all night will surprise you


In 2010, biologists studying Arabidopsis metabolism at an independent scientific research center discovered something very interesting: Their experimental plants seemed to use up their starch reserves at a very steady rate, every night using roughly 95% of what they started with.

If you remember your high school biology, during daylight hours, plants use sunlight to convert carbon dioxide and water (through photosynthesis) into carbohydrate compounds—AKA starches. Then, at night, they break down these stored starches to power their continued metabolism and growth.

What the team at the John Innes Centre had been doing was growing Arabidopsis in 12 hours of daylight followed by 12 hours of darkness. Throughout the 24-hour cycle, they measured both how much starch the plants produced and how much starch they consumed. They found that the rates were pretty linear, increasing and decreasing fairly steadily. You're probably thinking, "Big whoop. A steady metabolism rate. What's exciting about that?"

Well, read on. After four weeks of 12 hours light/12 hours dark, the researchers mixed things up. The very next day, they turned out the lights early for some of the plants—after only 8 hours of daylight instead of 12. Thus, the plants had only been making starch for 8 hours, not the usual 12. Then, 16 hours of darkness later, the scientists turned the lights back on. Notice this is still a 24-hour cycle, it's just skewed toward more darkness than light. So you might expect that these plants, accustomed to having their food last for 12 hours, would now run out when the night was 4 hours longer. But they didn't! They still had about 5% left—so, again, they used up about 95% of their reserves!

Meaning they changed the rate at which they were consuming starch to account for the changed conditions! And other plants that were given more light than they were accustomed to—now 16 hours of light followed by 8 hours of dark—also had 95% of reserves left at dawn. They had sped up their starch consumption, to account for the shorter night!

What did all this mean? The team concluded that plants must have a 24-hour biological clock that tells them how many hours of darkness to expect after a certain number of hours of light. Knowing how long your food has to last gives you a chance to pace how fast you eat. Who knew plants could do this?

The last segment below is from the same team of plant physiologists, who now think they have a mechanism for how plants determine their nighttime consumption rates. They're calling it molecular math. And though plants aren't really doing arithmetic, it is useful to think of it a type of calculation:

Amount of stored starch ÷ length of upcoming night = optimal rate of consumption.



Can plants do math?


This is Sandra Tsing Loh with the Loh Down on Science, saying maybe they can ..

See, during the day, plants use sunlight to convert carbon dioxide into sugars and starches. At night, they use these to maintain life and growth. But how do they pace their consumption so they don't run out before dawn?

Plant biologists in the U.K. have developed a model of the process. It's like a math problem: amount of stored starch divided by the number of hours of darkness equals consumption rate.

The model seems to match what they're finding in the lab. When they make the night artificially shorter or longer? Each change triggers a different "calculation." Short night ahead? Plants use starch more rapidly. Long night ahead? Use it more slowly.

The plants aren’t really doing division of course . . . the key is likely a biological clock, which helps them estimate the time til dawn. The biologists are calling it "molecular math."



END
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If you have light schedule info or any practical experience tests / results to share with others please do so any way you see fit.

Personally Im thinking of using a 6 on & 12 off for the last week of the flush.

My thought is the plants will make more crystal and terpenes in the longer dark period although I don't know what it'll do..


The below statement was reported some years ago after conducting tests


The Stichting Institute of Medical marijuana (SIMM), the first company to sell marijuana through the pharmacies of Holland, has been investigating the medical possibilities of cannabis, together with TNO laboratories and the University of Leiden.

One of their discoveries has been that to keep the ripe plants in the dark before harvesting could increase their potency.SIMM’s growers separated a crop of mature plants, harvested half of them and kept the other half in absolute darkness for 72 hours before cutting and drying. Analysis of the resulting dried buds showed that some varieties had seen an increase of THC while CBD and CBN remained the same."


Have any Thoughts or info to add ?
 
It seems they count both the dark period and light period then do some math and meter their starch consumption.

Using their inner 24 hour clock ... I'm curious what happens if you use a 18 hour clock schedule ? haha

6 on 12 off


Quote

they changed the rate at which they were consuming starch to account for the changed conditions! And other plants that were given more light than they were accustomed to—now 16 hours of light followed by 8 hours of dark—also had 95% of reserves left at dawn. They had sped up their starch consumption, to account for the shorter night!

What did all this mean? The team concluded that plants must have a 24-hour biological clock that tells them how many hours of darkness to expect after a certain number of hours of light.


:volcano-smiley:
 
Yeah I read that part. Was more thinking of this part
The clock counts down at night. When it's dark, phytochrome molecules that are in the Pfr form start converting to Pr at a slow, steady rate.
and how 'slow and steady' relates to the fact that plants seem to be able to catch most any little blink of light.
 
They are hyper sensitive to light tuned to allow only the dimmest of light like moonlight to go unnoticed ( it seems to me )

Never heard of a issue caused by a dark period in the day period , it may go by unnoticed ?

Quote ~

Plants got rhythm. The phytochrome clock enables plants to establish a 24-hour circadian rhythm. For plants that open their flower petals at dawn and close them at dusk, the phytochrome clock allows them to anticipate the sun’s rise and set. In fact, when placed in a dark closet, these plants will continue to open and close their flowers right on schedule for a number of days, until the circadian rhythm finally dampens.
 
I'm curious what happens if you use a 18 hour clock schedule ? haha 6 on 12 off

That's an interesting question. How much is the cycle hard wired and how much adaptive?

I'm reminded for some reason of the studies the Max Plank Institute researchers did, having people live in rooms in caves with everything they could want except access to any external time reference. Many of them went on 25 hour circadian rhythms... so it appears we need external cues to keep constantly syncing our internal clock to the external world. Golly, had a bit of honey oil before I went out for my walk. Can you tell? ;)
 
I was wondering how much is adaptive as well , it could be they will adapt to a 18 hour schedule after one to two nights.

Don't know how would be able to tell if they adapted or not as my skills at measuring starches are severely lacking.

I found a new improved problematic idea to test out with a 36 hour schedule ,12 on 24 off


I'm thinking the increased dark period might help increase the trichome and terpene presence

Tomorrow the plants are on day 10 of the flush with a week or more to go

WTF they are starting their first 24 hr dark period right now / tonight ( followed by 12 on )

..Maybe 36 hrs off 12 on for a 48 hr schedule .:volcano-smiley:
 
After considering the effects decided to give them a 36 hr dark period with 12hrs on

They have now completed the first 19 hrs of the 36 hr dark period 17 hours to go before lights on.

I'm pretty excited to try this out and should have the results in about 8 days , four 48hr plant days.

Time flies when your having Fun !

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Food for thought

Speed up the cycle with a clock reset ?

Want to speed up your switch from veg to flower? Give plants an uninterrupted 24-36 hours of darkness before going to a 12-12 cycle. It will make more of the Far-Reds change into Reds, giving a more powerful signal to your plant that it is time to bloom. Normally, the transition can take a couple of weeks to be seen on your plants. By giving them a really long night, you can speed this up dramatically.

The dark side

The way in which plants can go “wonky” and revert to vegetative growth is that just because a Far-Red receptor begins to work as a Red one, doesn’t mean that it can’t revert back. It takes several hours of continual darkness to change Far-Reds to Reds, but just a brief moment of bright light to change them back.
 
It's an interesting question. I have been wondering how an autoflower cannabis plant knows it's time to flower when it's on a 24 hour light cycle. Maybe ruderalis isn't just day length insensitive; maybe it's not using light for time measurement at all.

I think the Autoflower plants have a gene in them that allows this , it deserves further study if you come across anything of interest on it post it up and we can learn.


It must be an adaption in the Rudurelis family caused by oddball hours like 20 and 24hrs light. A mechanism that works as a Age clock gauge ?



Here's something interesting


Scientists develop a tomato plant that can grow all night


It could be a tomato game-changer: Scientists have discovered a gene that would allow commercial tomato plants to tolerate 24 hours of light a day.

In theory, more light exposure means more energy production for the plant, so the discovery could lead to tomato plants that yield up to 26% more tomatoes compared with plants that are given 18 hours of light in a greenhouse setting, the Netherlands-based researchers wrote in a paper published Tuesday in the journal Nature Communications.

Scientists are not sure how widespread continuous light tolerance is throughout the plant world. Pepper plants, rose bushes and lettuces are all perfectly happy when the lights never go off, but as botanists first discovered nearly 100 years ago, tomato plants are different.

"At the beginning, yellow spots appear and they look like they need some fertilizer," said the study's lead author, Aaron Velez-Ramirez of the Laboratory of Plant Physiology at Wageningen University in the Netherlands. "If the plant is left in continuous light long enough, the complete plant turns yellow and dies."

The closest relative of domesticated tomatoes is also sensitive to continuous light, but all other strains of wild tomatoes are just fine in a world that never goes dark.

The researchers are not sure how this tolerance benefits the plants in the wild, because the lights always do go out in nature, but that is beside the point of this particular study. The main objective was to figure out which gene or set of genes was responsible for keeping wild tomato plants alive in continuous light, and to see if it could transferred to domesticated tomatoes.

Over the course of a multi-year study, the researchers found that the expression of a gene called CAB-13 seems to be a key player in bestowing light tolerance on wild tomatoes, and that this expression could be successfully transferred to commercial tomatoes over several generations of selective crossbreeding.

"It would be like crossing a dog with a wolf and then crossing back the descendants many times with dogs to get rid of all undesirable wolf characteristics but the one you want," Velez-Ramirez said.

By the end of the study, the researchers were able to grow a domesticated tomato that could tolerate 24 hours of light. They report that under those conditions, it produced 20% more fruit than plants exposed to 18 hours of light.

Their preliminary tests suggest that CAB-13 has an effect on the carbohydrate metabolism and photosynthesis of tomato plants, but it does not seem to have an effect on plant development or the fruit itself. However, more tests are needed before a 24-hour light-tolerant tomato plant will come to market.

The study was done in conjunction with researchers at Monsanto Holland, and Monsanto holds the patent on these light-tolerant tomato plants.

It should also be noted that, according to the Food and Agricultural Organization of the United Nations, production of tomatoes ranks eighth among agricultural commodities worldwide -- higher than any other fruit or vegetable.
 
After considering the effects decided to give them a 36 hr dark period with 12hrs on

They have now completed the first 19 hrs of the 36 hr dark period 17 hours to go before lights on.

I'm pretty excited to try this out and should have the results in about 8 days , four 48hr plant days.

How did this turn out? What was your hypothesis?

Gonna drop this link here, it's another good read on phytochrome.
Phytochrome
 
I tried a weird 6on 2off cycle for the veggies for a little while. Read on the interweb somewhere that this would be good for your plant. Turned out that all it did was stress the girls out, and one went into preflower which was not desirable. They are now back on 18/6.

My take home from that was to remember that these are plants, and the sun doesn't go on and off every 6 hours. They would of course be able to tell how many hours are in a normal day cycle so they were expecting a normal 24hr day. I confused them when a full day turned into 8 hours. Message for me being - replicate nature, not someone's opinion on the interwebs.

Maybe it is possible to change this a bit to push the girls harder, but I think slow change is better and only within the possible extremes of what a plant growing outside (anywhere in the world) would experience. The includes long night periods (8on/16off) in the dead of winter and 24/0 at the end.

In my limited 18 months of growing, I have always given my girls a 24hr - 36hr darkness period just before harvest. Two reasons being (a) stop any remaining nutes (after flush; residual type) from going back up into the flowers for taste reasons, and (b) I believe that this makes the plant really believe that it's the end - so she gives it a bit more right then. My 2c :)
 
Very Interesting read!
This partially explains why my ladies begin praying 30 minutes BEFORE lights on! They seem to "know" just what to expect and when to expect it...TO THE MINUTE, each day after 12hrs of darkness. I watch them with an old Pet monitor with Night Vision...So cool to watch.
:morenutes:
 
How did this turn out? What was your hypothesis?

Gonna drop this link here, it's another good read on phytochrome.
Phytochrome

Hey good question I had forgot to post back with the result

So I used a 48 hr light schedule

12 On 36 off for the last week before harvest the buds continued to grow and swell as normal with good trichome production.

The Stone

It has a clean pleasant high the kind you get from well flushed Bud smooth and silk like.

But .... It lacks the eye numbing sting I have gotten from plants before after pre harvest stressing.

I have noted after drilling holes in a plant stalk a few days before harvest the high the plant produced was near blinding , causing the eyes to feel swollen and puffy with a strong buzz to match.

So inclusion I found the results to be less then impressive I will try something different next time , maybe do a stalk drilling one on one test.

This batch of bud only half blinds me / half puffs up my eyes the other shit was ridiculous i felt Like I was very sleep deprived. Haha no shit

Harvest day was 2.5 weeks ago as of yesterday its cured to 62% humidity and is now ready for storage.
 
Great read! It gives much to think about.

Also, I now want to use a pet camera like Buzzer777. :)
 
Im wondering now if a night period is good for the veg cycle. Ive heard the is no empirical data for cannabis.

My autoflower seems to be doing fine after 43 days of nonstop light. I wonder if photoperiod plants would be more sensitive. Someone should to an experiement!
 
Its hard to say for sure whats best without extensive testing but it stands to reason that you want the plant to be nourished throughout the day so it has plenty of stored energy to complete its night processes.

You may want to check on it but the way I understand it is in the Day time plants convert c02 and nutrients to energy in the form of sugars and carbs that it will use for its night time growth period.

this article Photosynthesis | Sambal's Science Web is helpful

from article:

Plants can make enough glucose on a sunny day to last them through the night and through lots of cloudy dark days, but they cannot store up lots of glucose. What they do is convert the extra glucose into starch. When they need to use the energy, they can turn the starch back into glucose. Starch can be stored in leaves or other parts of the plant. they can turn glucose into sucrose: this is a sugar carried around the plant in special tubes called phloem.
 
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