The more dialed in your VPD is the better your plants are going to look overall. VPD is just one of the variables tho to a healthy plant. The longer my environment stays in a good VPD along with perfect PPFD the more I see my plants praying.

Happy growing! Your plants look very nice, and those pots look awesome haha.

blueicegrows said:

The more dialed in your VPD is the betted your plants are going to look overall. VPD is just one of the variables tho to a healthy plant. The longer my environment stays in a good VPD along with perfect PPFD the more I see my plants praying.

Happy growing!

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It's just such a debated topic on whether praying is good or bad because there literally zero scientific studys that have come to a conclusion of how and why.

What's funny is the leaves that are not praying are the ones in a better VPD range and they're all under the same ppfd. Leaves that are praying have higher VPD.

On the flip side of a statement in my original post,
Sometimes turning up your light will stop praying as well, another reason there's no definitive answer, but to much light can cause the stomata to close and avoid water loss through transpiration which would slow regardless of current vpd values.
Which lines up with my theory less transpiration, less praying.

My plants pray when they uptake the nutrients that I give. Usually lasts about 12 -24 hours.

BB22 said:

My plants pray when they uptake the nutrients that I give. Usually lasts about 12 -24 hours.

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Right on, just raises more questions for me lol
Nutrients regulate opening and closing of stomata, stomata controls transpiration. Stomata open from nutrients which leads to more transpiration which leads to leaves praying?
Who knows lol

It's always been my view that when the leaf prays it's liking the enviornment. Your plants look very happy Newty

I always think that is a good sign that they are ready for more light.

Praying leaves = nothing to do with stress. All about being happy.

Praying leaves are the perfect sweet spot for the plant. It's normal for them to pray after watering as well. Consider praying leaves to be a healthy sign of a fast growing plant. Nothing to worry about unless your leaves are turning yellow. Praying leaves is also a sign of a specific pressure coming from the plant itself, i will find the name of it and post back. Praying leaves means your plants are in the perfect environment and loving it.

Turgor Pressure Cannabis Plants "Praying" .

This ability to develop enough water pressure in the trunk and in the stems of the leaves to lift them up like this is the result of maximum transpiration. This means that the leaves are getting enough energy from the light to evaporate enough water from the leaves so as to create maximum suction up through the roots, giving you maximum uptake of water and nutrients from the soil. This is an indication that all is as it should be, and the leaves are pointing toward the thing that is most important to the plant at the moment, the light.

Potassium has a role to play in maintaining turgidity of stomatal guard cells. Turgor is the pressure exerted by water inside the cell of the plant. A sufficient level of turgor pressure should be maintained so that the plant keeps growing. Without sufficient turgor pressure within plant cells, plants will wilt.

Turgor pressure helps keep a plant standing upright with its leaves outstretched or tipped up to absorb as much light as possible. When turgor pressure is high, this allows maximum expansion of cannabis leaves to receive adequate or more sunlight.

Yellow leaves often result from nutritional deficiencies. But if you know the nutrient situation is optimum and observe the praying leaves go from green to yellow, it could be triggered by light stress. In that case, you may move the lights further away or rotate your plants around to allow the stressed leaves to get more shade.

Among cannabis growers the term “praying” referring to the cannabis plants gets bandied about, turgor pressure scientifically defines plant cell rigidity and why cannabis leaves appear to be “praying” towards the light. Cannabis leaves will expand outwards as much as possible when turgor pressure is high. This allows for the expansion of cannabis leaves allowing for more adequate sunlight. If you see your plants reaching towards the light and they appear healthy overall, then I would be saying hallelujah in rejoice.

Resources:​

1. Cram W.J. (1976) “Negative Feedback Regulation of Transport in Cells. The Maintenance of Turgor, Volume and Nutrient Supply.” In: Lüttge U., Pitman M.G. (eds) Transport in Plants II. Encyclopedia of Plant Physiology, vol 2 / A. Springer, Berlin, Heidelberg.
2. Zimmerman, U. (1978). “Physics of Turgor- and Osmoregulation”. Ann. Rev. Plant Physiol. 1978. 29:121-48. Institute of Biophysical Chemistry, Nuclear Research Center, Julich, FRG.
3. Dietrich & Keller. (1991). “Turgor Pressure”. Science Direct. Advances in Agronomy.
4. Villarreal, Mariana Ruiz. LadyofHats. (2007). “Turgor Pressure on Plant Cells Diagram”. Wikimedia Commons - Public Domain.

Newty said:

Right on, just raises more questions for me lol
Nutrients regulate opening and closing of stomata, stomata controls transpiration. Stomata open from nutrients which leads to more transpiration which leads to leaves praying?
Who knows lol

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Your using too much light if they aren't praying. I had that issue for years when i first started. Thought everyone else was using too little light and that is why they were reaching for it aka praying for more light . If you have cannabis at 750-850 umols², your plants will start praying. Get a cheap ppfd reader. I got mine for 75 bucks on Amazon.

I_GROW_SKUNK said:

Your using too much light if they aren't praying. I had that issue for years when i first started. Thought everyone else was using too little light and that is why they were reaching for it aka praying for more light . If you have cannabis at 750-850 umols², your plants will start praying. Get a cheap ppfd reader. I got mine for 75 bucks on Amazon.

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This is not about if the plants have enough light.
I know how to grow and I do have equipment to read ppfd.

I'm not even asking why my plants are praying or help with my grow, I found a pattern that makes sense and wondering everyone's thoughts.

The other half would say praying leaves means to much light and the leaves are hiding from it.

But then why would both turning up the light and turning down the light cause the leaves to stop praying?
If it was indeed only lighting related then the leaves would only stop praying if you turned the light up or down, not both.

If you read my post and my replies, there's a pattern of transpiration which light, nutrients, and stomata opening and closing all relate to each other.

Newty said:

This is not about if the plants have enough light.
I know how to grow and I do have equipment to read ppfd.

I'm not even asking why my plants are praying or help with my grow, I found a pattern that makes sense and wondering everyone's thoughts.

The other half would say praying leaves means to much light and the leaves are hiding from it.

But then why would both turning up the light and turning down the light cause the leaves to stop praying?
If it was indeed only lighting related then the leaves would only stop praying if you turned the light up or down, not both.

If you read my post and my replies, there's a pattern of transpiration which light, nutrients, and stomata opening and closing all relate to each other.

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Your asking for opinions and then get mad when someone says something other than what you think. Oookkkkk pal.

I_GROW_SKUNK said:

Your asking for opinions and then get mad when someone says something other than what you think. Oookkkkk pal.

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I'm not mad, don't have time for that.

You came out and said my lights are to high and to buy ppfd equipment,
How was I supposed to take that?

I offered a rebuttal to keep conversation going and to sum up 2 of my posts into 1.

There's 2 major differences with this grow.

1. I usually run my lights in this tent at 30%-40% power and 30" height during veg
- This grow I kept my lights higher in the tent at same power, currently 48" over canopy at 40%

Even though the tent is at the same temp as previous grows, the light is higher at the same intensity so leaf temp will be lower and as a result VPD/Transpiration lower.

2. Humidifier is in my tent instead of lung room.
- My tent does not have an even VPD across the tent, the plants getting the mist/humidity 1st have a lower VPD/Transpiration rate.
Plants getting mist/humidity last (my praying leaves) have a higher VPD/Transpiration rate.

Verified with AC Infinity VPD IR Thermometer.

Praying leaves is always referenced with light intensity, is it just the fact the Transpiration rate changes when you turn up or down your light intensity?

If that's the case, adding or removing humidity could have the same result so now I'm going to move my Humidifier from tent and put it in my lung room, in a few hours my tent will be an even VPD, let's see if all the leaves are at the same angle after stabilization.

Newty said:

There's 2 major differences with this grow.

1. I usually run my lights in this tent at 30%-40% power and 30" height during veg
- This grow I kept my lights higher in the tent at same power, currently 48" over canopy at 40%

Even though the tent is at the same temp as previous grows, the light is higher at the same intensity so leaf temp will be lower and as a result VPD/Transpiration lower.

2. Humidifier is in my tent instead of lung room.
- My tent does not have an even VPD across the tent, the plants getting the mist/humidity 1st have a lower VPD/Transpiration rate.
Plants getting mist/humidity last (my praying leaves) have a higher VPD/Transpiration rate.

Verified with AC Infinity VPD IR Thermometer.

Praying leaves is always referenced with light intensity, is it just the fact the Transpiration rate changes when you turn up or down your light intensity?

If that's the case, adding or removing humidity could have the same result so now I'm going to move my Humidifier from tent and put it in my lung room, in a few hours my tent will be an even VPD, let's see if all the leaves are at the same angle after stabilization.

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Well of course humidity matters. It has to be in the perfect range to get the full Monty from the plant. It requires both ime.

After moving humidifier out of tent and into my lung room and running it, my VPD/Transpiration rate is now stabilized throughout the whole tent, as you see from my tent camera picture there's no more praying.

Now I'm going to turn off my humidifier to raise VPD/Transpiration rate, let's see if they start praying again and if all them do with the same VPD throughout.

I know changing my environment back and forth can cause unwanted stress but I'm trying to eliminate some bro science from the equation with real world tests.

I researched this question several times in the past. There isn't much information to be found. After I saw this thread, I looked some more. That included watching an hour-long Bruce Bugbee video about light. He didn't mention praying leaves, so I wrote to him to ask about it specifically. I'll let you know if he responds.

In the video, which I had seen previously, he talked about how much light plants can use. Unfortunately, he doesn't specifically address praying leaves. His assertion, nevertheless, is that the amount of light cannabis can use depends on other growth factors. If they're all optimal and balanced, then the plants can use high light levels. Here's a screenshot and a link:

My leaves were praying again.

So far my results show that when the plants are at the proper VPD/Transpiration rate, they do not pray.
When the leaves are higher then proper VPD/Transpiration rate, they pray.
Both the tests ran were at 1 temp, I only changed VPD with Humidity.

I will let my plants be for today since changing my environment probably caused minor stress.

Tomorrow I will turn on my Humidifier again and stablize humidity and change VPD/Transpiration rate with only temp this time and see if the results are the same.
If those results are the same as far as VPD level and praying leaves then
I will then keep the same environment temp and humidity while raising and lowering individual plant leaf VPD directly without altering tent conditions and see if they pray and stop praying.

According to what I've read so far, there are multiple potential causes of praying leaves, and they can be either good or bad. They're good if they're on a green, fast-growing plant. Conversely, leaves may be getting too much light if they look bleached with yellow tips. Additionally, sometimes praying leaves can be caused by high heat, low humidity or root problems.

LoveGrowingIt said:

According to what I've read so far, there are multiple potential causes of praying leaves, and they can be either good or bad. They're good if they're on a green, fast-growing plant. Conversely, leaves may be getting too much light if they look bleached with yellow tips. Additionally, sometimes praying leaves can be caused by high heat, low humidity or root problems.

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Absolutely understand that.

I'm getting repeatable data by just simply changing vpd/transpiration rate.
Being able to control it by simply changing humidity and leaving everything else the same says a lot, at least for this strain.
I can make all the plants pray or not pray within 2 hrs of humidity change, every single time.

Tomorrow or Saturday we will see if steady humidity and temp changes does the same.

I don't think I actually have an issue with my grow. Just noticed a pattern that was interesting and decided to do real world tests.