Cannabis and its response to light (a discussion about leaf lift)

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Hippy_BiotabsF70

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I have to say I’m not entirely convinced leaf lift is a sign of being happy?

I think EOF hit the nail on the head. It’s something to do with too much or too little light I believe. I see it most on outdoor plants.

I don’t think it’s basking in the light as people say. I think when a plant is happy and the leaves are working hard as little solar panels, they will actually be flat and spread out. Giving as much surface area to the plant as possible.

Also I think the bending leaves to follow the sun is a different thing?


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FullDuplex

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I have to say I’m not entirely convinced leaf lift is a sign of being happy?

I think EOF hit the nail on the head. It’s something to do with too much or too little light I believe. I see it most on outdoor plants.

I don’t think it’s basking in the light as people say. I think when a plant is happy and the leaves are working hard as little solar panels, they will actually be flat and spread out. Giving as much surface area to the plant as possible.

Also I think the bending leaves to follow the sun is a different thing?


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I would agree but you usually see leaf curl or "Taco" leaf if there is too much light, it can be as simple as the leaf tips starting to raise all the way to the folded fingers.

I've seen it now in 2 different generations of the ALF, and both times it's been aggressive. First plants are a multi pot, tall one is doing it, sister in the same pot is not. Same environment and feed due to them sharing a pot.


Here are 2 ALF 5 same room different hydro containers but as you can see one is super aggressive with this.


 

orrganic

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On the thread of the leaves following-the-light phenomenon, it as very real and it is called phototropism.. Cells in the stem of the leaf elongate on the shady side, This bends the stem towards the the light.

It works on very short timescales. On a summer day here in Alaska, the sun has about a 250 degree path across the sides. For survival in Alaska, plants compete for photons throughout a 20 hour summer day. The species that survive have adapted to exploit phototropism. On a clear day, the cottonwood and birch leaves face to the NE in the morning and phototropism will turn them to track with the sun South at 1:00 pm and NW at 11:00 PM at sunset.

As a matter of course, I rotate my indoor plants about 120 degrees every watering 2-3 times a week.

Amnesia (2-3 wks out) , White Widow( funky plant 3 wks out), Autokush (month out), bubble gum (month out)
I've thought about this lots too @wxguys post explains perfectly.

I actually started a thread in the infirmary for three plants that were praying too/preying on the light so much I was worried.

They were Sweet seeds Ice Cool under COBs


And a Sweet Seeds SFLK under the sun bending 90° sideways.
 
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Doogal

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This was a really interesting read and some great points were brought up. I just wanted to chime in and keep the discussion going :)
I would just like to point out that what I'm about to say is what I've picked up from growing non cannabis based plants for a long time and I'm not specifically referencing cannabis plants here, but making a generalisation about all plants. Its been a while since I have thought about this properly so I would check my facts in wikipedia or somewhere that you trust in case my old brain is having a mega fart. P.S. I'm not great at explaining things that kinda make sense in my weird little brain and then writing them down so apologies if this is a massive of jumble of incoherent rubbish :)

I've had this 'praying' stature show up on hundreds of different plants that I've grown over the years and my personal conclusion has been that there are MANY reasons for it, but most importantly I think is to recognise why its happening at different times during the plants life and what it means at each specific stage.

Wxguy was in fact correct when he talked about phototropism being the reason behind it, however plants have a few different 'tropisms' that affect them and we have to look more closely at the tropisms as a collection to see why plants do certain things.

So what is a tropism? A tropism simply refers to the movement or growth of a living organism in response to environmental stimulus, with phototropism being a response to light which can be negative or positive, so a growth towards or away from light.

There are a vast number of tropisms, many that I have not heard of.
Where plants are concerned we can look at a couple of tropisms that specifically determine their reasons for growth in certain ways.

Phototropism - growth towards/away from light. This also encapsulates light colour, so a lot of these fancy LED lights that let you choose a specific colour spectrum can instigate phototropism in different ways.
Geotropism or Gravitropism - this is the plants response to gravity and it can also be positive and negative. Roots adhere to negative geotropism by growing downwards towards gravity and stems (when not externally manipulated) have a positive geotropic growth upwards, fighting against gravity, with the aid of phototropism (in most cases)
Hydrotropism - response to water. This is mainly to do with root masses 'sensing' water within a substrate and growing in that direction.
Hygrotropism - response to humidity
Chemtropism - response to chemical stimulus

There are many more, however I think those ones are probably the most important ones where a cannabis plant is concerned. Incidentally @orrganic I think the picture you provided above is an example of plagiotropism which is in fact a type of geotropism.
If you look right at the bottom of this article you can see a description of it, which is basically the best I could find for you without photocopying one of my science books
http://plantsinaction.science.uq.edu.au/edition1/?q=content/8-2-1-gravitropism

That website above is a link to a brilliant book, all the chapters are there. Its old school science but it factual at least :)

So now that we know what kind of stimulus plants respond to, in order to find the reasons for this 'praying' you have to look at what stage of growth the plant is in. The reason for that is all down to phytohormones which are the plants hormones. Like humans, plant hormones are present at various stages in a plants life, in different concentrations and in different parts of the plant.

There is something called the Cholodny–Went model (https://en.wikipedia.org/wiki/Cholodny–Went_model )
I don't know a whole lot about this to be honest with you, mainly because its specifics have been disputed, but it has largely stood the test of time because it gets a lot of things right.
The thing that bothers me with this model is the hypothesis that auxin is the only phytohormone that lends towards geotropism and phototropism, which I don't personally think is true, but hey I'm no genius and that guy probably was, so what do I know?

So what I'm trying to say is that depending on the stimulus in question, you have to consider what stage the plant is in its life in order to determine which particular phytohormones it is producing and then you can begin to explain why your plant is doing certain things.
Plant hormones are some of the most vital chemicals within any plant as they regulate pretty much everything that a plant does from seedling to death.
Having a look here : ( https://en.wikipedia.org/wiki/Plant_hormone ) you can see that plant hormones affect seed growth, time of flowering, the sex of flowers, senescence of leaves, and fruits. They affect which tissues grow upward and which grow downward, leaf formation and stem growth, fruit development and ripening, plant longevity, and even plant death.
(I have just copy and pasted that from the article by the way)

With this in mind, we can look at auxins in particular. They are present pretty much throughout the entire lifetime of the plant I believe and they certainly do lend towards phototropism and geotropism. Auxins exist across the entire plant, however their concentrations vary.
The plant will use the different concentrations of auxins as information on how to develop and also where to develop. So a plant that contains a great concentration of auxins in particular areas will see an area where it is getting a lot of information from.
Now this is the bit that I am a bit unsure of, I think that what happens is auxins are present greatly in elongated cells which in turn are present on parts of a plant that are the farthest away from their light source. The auxins themselves move throughout the plant using active transport and this requires cellular energy which is why a lot of people say that it happens on 'healthy looking' plants.
The plant needs to be creating energy for its processes to occur correctly, mostly. This roughly translates into being healthy.

The tip of a plants stem is another source of information, however I forget the name of this, sorry.
Combine these two sources of information and that is generally enough for the plant to know which direction to grow in. This is why you see a lean towards the sun in outdoor plants < that is a mass generalisation I know, but it was the easiest example I can think of lol.

Now in an indoor grow room where the light source is much closer to the plant and in a 'boxed off area' so to speak, usually within a tent or room, the light can seem omnidirectional due to reflecting surfaces, however it will have an original source (the bulb) which is elevated above the plant and generally does't move like the sun would outside. If you consider that it is entirely possible for a plant to have similar concentrations of auxin and other phytohormones across most of its areas/cells, then in turn it is entirely plausible for a plant to respond in that praying fashion at any point of its life.

Also I wouldn't overlook geotropism having a lot to do with this as plants seem to respond to light and gravity in coherence with each other from what I have learned. Even looking into plants 'breathing in' when their roots respond to geotropism and hydrotropism as possible things that help towards praying isn't beyond the scope of reality. There is nothing to suggest that a plant responding to geotropism, phototropism, hydrotropism and hygrotropism all at the same time can't look like this.
 
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fryge

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I grow outdoor, and especially one of my strains/crosses strongly exhibits leaf movement, especially bending downards at night.

I think the leaves bending down at night must be linked to the circadian rhythm(internal clock, 24 hour rhytm), since I've observed they start bending the leaves downard 1-2 hours before sunset(not sure about sunrise, since that's usually while I'm sleeping).

I'm not sure what the purpose is, if there even is one, your theory about water seems unlikely to me, since the force driving water to move up in the plant is caused by the sun shining on the leaf and water evaporating trough the stomata, a pull. there is a push from the roots, but usually that force is smaller, only in some cases(early morning or high humidity) the rootpush will be bigger, and you'll see that as guttation. so a plant doesn't save up water before the day, since the pump is caused/powered by the water leaving.

however, purely guessing, I would think praying is due to light, not water. for light interception, horizontal would be best. the bending downards at night might be a little matter of efficiency, since at night there is no light to intercept anyway, and a leaf hanging downwards requires less 'energy' to keep up(better said, less rigidity in the leaf stem), maybe it can also handle wind a little better, and maybe with the leaves downwards it keeps a little more warmth close to it.

the praying I would guess is a response to too much light(and a seperate response from the downward bending at night). I know there are some other mechanisms to too much light, for example the chloroplasts will move within the cell based on how much light the leaf gets. if there's too much light, which could damage the chloroplasts, they all move to the cellwals and stack underneath eachother, so that only the upper ones get damaged, but they shield/shade the ones below.
I could imagine that praying is a similar response, to reduce the amount of light hitting the leaf. (that would also explain you see it less indoors, as the sun is much more intense)

btw, I'm not sure wether this leaf movement would fall under the definition of phototropism.
I do think it's a response to light, but usually when you talk about phototropism, you're talking about growth. the growing tip of a plant behind a window bending towards the window is phototropism. but in that situation, the movement goes together with growth, and the growth also causes the movement(trough the shaded side of the stem growing more).
but in this case, the leaf petiole moves without growing. can't be caused by the same mechanism, since the petiole is not elongating anymore. and you would see it in the tops, not the individual leaves, if it was regular phototropism.
 
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fryge

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it's been a while, but I just stumbled upon the official name of the movement of leaves before/during night: https://en.wikipedia.org/wiki/Nyctinasty.
The purpose of, and conferred benefits of nyctinastic movement have yet to be identified. Studies using mutant plants with a loss of function gene that results in petiole growth instead of pulvini found that these plants has less biomass and smaller leaf area than the wild type. This indicates nyctnastic movement may be beneficial toward plant growth.
and plants 'praying' towards the sun is called https://en.wikipedia.org/wiki/Heliotropism
 
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DTOM420

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Ok, I’m still left confused about all this. I have 2 Chrystal Aurora Autos that is growing from beans I got from New420Guy Seeds. These 2 plants spent 10 days under a 4 bulb T5 fixture with 6500K bulbs running 24/0 and about 3”-4” above them. They started in 16oz solo cups filled with FF Happy Frog soil nixed with FF Light Warrior seed starter soil and served only distilled water with myco added to it. They looked like this when I went to transplant them......

A255D663-74BE-4B97-82BD-3901126CD113.jpeg
8EBF81A1-454B-4A16-A8D8-A008814454C6.jpeg


Then, I went to transplant them into 10 gallon grow bags with Happy Frog soil on the top half and FF Ocean Forest on the bottom half of the bag. I watered the 2 plants prior to transplant with distilled water with 1/3 strength House & Garden Root Excelurator Gold mixed in. I remove the bottom of the cups with a razor plate and make skits up the side. Then, I drop the cups I to a home made to fit them perfectly , complete a couple of the slices in the cup and pull the remnants of the cup out of the soil - a virtually stress free transplant method. I did the transplant about 2hrs before dark. This was their first night outside and they were in a partially shaded spot to give them some protection from the scorching sun here. The following morning I went to check on them and found them “praying” but otherwise looking great. They have been growing well but they remain in that praying stance 24hrs a day. It kinda freaked me out and I found this thread hoping to determine if they’re adjusting to outdoors OK. I think that they are but I’m still not sure; and I damn sure don’t u derstabd why they’re suddenly doing this when they were looking like a photo perfect indica under the fluorescents.

Here’s how they look today......

BC849854-DDBF-4336-880E-5C866A36AFEC.jpeg
22DBA4AB-E1CB-4123-AE4F-CEBB06B69C34.jpeg


So, ARE my 2 girls fine? What’s causing them to do this suddenly?
 

Rev. Green Genes

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This was a really interesting read and some great points were brought up. I just wanted to chime in and keep the discussion going :)
I would just like to point out that what I'm about to say is what I've picked up from growing non cannabis based plants for a long time and I'm not specifically referencing cannabis plants here, but making a generalisation about all plants. Its been a while since I have thought about this properly so I would check my facts in wikipedia or somewhere that you trust in case my old brain is having a mega fart. P.S. I'm not great at explaining things that kinda make sense in my weird little brain and then writing them down so apologies if this is a massive of jumble of incoherent rubbish :)

I've had this 'praying' stature show up on hundreds of different plants that I've grown over the years and my personal conclusion has been that there are MANY reasons for it, but most importantly I think is to recognise why its happening at different times during the plants life and what it means at each specific stage.

Wxguy was in fact correct when he talked about phototropism being the reason behind it, however plants have a few different 'tropisms' that affect them and we have to look more closely at the tropisms as a collection to see why plants do certain things.

So what is a tropism? A tropism simply refers to the movement or growth of a living organism in response to environmental stimulus, with phototropism being a response to light which can be negative or positive, so a growth towards or away from light.

There are a vast number of tropisms, many that I have not heard of.
Where plants are concerned we can look at a couple of tropisms that specifically determine their reasons for growth in certain ways.

Phototropism - growth towards/away from light. This also encapsulates light colour, so a lot of these fancy LED lights that let you choose a specific colour spectrum can instigate phototropism in different ways.
Geotropism or Gravitropism - this is the plants response to gravity and it can also be positive and negative. Roots adhere to negative geotropism by growing downwards towards gravity and stems (when not externally manipulated) have a positive geotropic growth upwards, fighting against gravity, with the aid of phototropism (in most cases)
Hydrotropism - response to water. This is mainly to do with root masses 'sensing' water within a substrate and growing in that direction.
Hygrotropism - response to humidity
Chemtropism - response to chemical stimulus

There are many more, however I think those ones are probably the most important ones where a cannabis plant is concerned. Incidentally @orrganic I think the picture you provided above is an example of plagiotropism which is in fact a type of geotropism.
If you look right at the bottom of this article you can see a description of it, which is basically the best I could find for you without photocopying one of my science books
http://plantsinaction.science.uq.edu.au/edition1/?q=content/8-2-1-gravitropism

That website above is a link to a brilliant book, all the chapters are there. Its old school science but it factual at least :)

So now that we know what kind of stimulus plants respond to, in order to find the reasons for this 'praying' you have to look at what stage of growth the plant is in. The reason for that is all down to phytohormones which are the plants hormones. Like humans, plant hormones are present at various stages in a plants life, in different concentrations and in different parts of the plant.

There is something called the Cholodny–Went model (https://en.wikipedia.org/wiki/Cholodny–Went_model )
I don't know a whole lot about this to be honest with you, mainly because its specifics have been disputed, but it has largely stood the test of time because it gets a lot of things right.
The thing that bothers me with this model is the hypothesis that auxin is the only phytohormone that lends towards geotropism and phototropism, which I don't personally think is true, but hey I'm no genius and that guy probably was, so what do I know?

So what I'm trying to say is that depending on the stimulus in question, you have to consider what stage the plant is in its life in order to determine which particular phytohormones it is producing and then you can begin to explain why your plant is doing certain things.
Plant hormones are some of the most vital chemicals within any plant as they regulate pretty much everything that a plant does from seedling to death.
Having a look here : ( https://en.wikipedia.org/wiki/Plant_hormone ) you can see that plant hormones affect seed growth, time of flowering, the sex of flowers, senescence of leaves, and fruits. They affect which tissues grow upward and which grow downward, leaf formation and stem growth, fruit development and ripening, plant longevity, and even plant death.
(I have just copy and pasted that from the article by the way)

With this in mind, we can look at auxins in particular. They are present pretty much throughout the entire lifetime of the plant I believe and they certainly do lend towards phototropism and geotropism. Auxins exist across the entire plant, however their concentrations vary.
The plant will use the different concentrations of auxins as information on how to develop and also where to develop. So a plant that contains a great concentration of auxins in particular areas will see an area where it is getting a lot of information from.
Now this is the bit that I am a bit unsure of, I think that what happens is auxins are present greatly in elongated cells which in turn are present on parts of a plant that are the farthest away from their light source. The auxins themselves move throughout the plant using active transport and this requires cellular energy which is why a lot of people say that it happens on 'healthy looking' plants.
The plant needs to be creating energy for its processes to occur correctly, mostly. This roughly translates into being healthy.

The tip of a plants stem is another source of information, however I forget the name of this, sorry.
Combine these two sources of information and that is generally enough for the plant to know which direction to grow in. This is why you see a lean towards the sun in outdoor plants < that is a mass generalisation I know, but it was the easiest example I can think of lol.

Now in an indoor grow room where the light source is much closer to the plant and in a 'boxed off area' so to speak, usually within a tent or room, the light can seem omnidirectional due to reflecting surfaces, however it will have an original source (the bulb) which is elevated above the plant and generally does't move like the sun would outside. If you consider that it is entirely possible for a plant to have similar concentrations of auxin and other phytohormones across most of its areas/cells, then in turn it is entirely plausible for a plant to respond in that praying fashion at any point of its life.

Also I wouldn't overlook geotropism having a lot to do with this as plants seem to respond to light and gravity in coherence with each other from what I have learned. Even looking into plants 'breathing in' when their roots respond to geotropism and hydrotropism as possible things that help towards praying isn't beyond the scope of reality. There is nothing to suggest that a plant responding to geotropism, phototropism, hydrotropism and hygrotropism all at the same time can't look like this.
:frog::frog::cool1:

Well written. And you made all the points I had planned while I was reading through this post. The most complete analysis I have read yet. And I went to Ag school.

:slap:
 

pop22

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Can't remember where i read it but a new theory is that the plant "tunes" the leaves when light is intense to better absorb certain spectrum, by changing the angle at which the light strikes the chloroplasts.

The post on growweedeasy about it being a sign the plant is getting too much light is just bs with nothing to support it. You need to be very careful with that site and winnow out the useful information. they use bots a lot to collect information and are not too choosy about filtering it or where they get it from....
Tacoing due to too intense light levels however is caused by the plant changing the shape of the chloroplasts to reduce the amount of light received by changing the exposed surface area and angle. be careful with this one though because very low RH can cause tacoing also.
 
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The post on growweedeasy about it being a sign the plant is getting too much light is just bs with nothing to support it.
Actually that is valid but not well explained. It is known as "light avoidance" a protective mechanism well known. I am not sure that cannabis leaves "praying" fits that mechanism exactly, but it plays into the process at some point. Our plants are typically well over the saturation point for photosynthetic radiation, and the plant will cool itself by thickening leaves to block some radiation, among other processes in it's tool belt. The Auxin compound is made in the leaves, it is light avoidant, and moves to the shady side of the leaf, this tightens up the petioles so the leaves stand up and you see an increase in transpiration because the increasing photosynthesis requires more water molecules to split and get H atoms for making NADPH and ATP.

If the plant has excess ATP it will slip into light avoidance mode and start storing it for later use and slow down on transpiration