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Rotala Wallichii spiral growth question

Katmanreef

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So I had a question for any of you that have grown Rotala Wallichii or any of the thin leaved rotalas. I noticed that sometimes the Rotala will grow in a spiral formation instead of having seperate/defined leaf nodes. Is there something that triggers this to happen or is it completely random? Here's a picture for reference:
20220523_195457.jpg

The one on the left is growing leaves in a continuous spiral, where as the one on the right has seperate leaf nodes. I'm just curious as to why this happens and if anyone else has seen this?
 
Yes I have. It's called a shift in the phyllotactic pattern and it is rather common.
Phyllotaxy describes the arrangement of leaves around a stem. Commonly this can be spiral or whorled, and that is what you are observing.

In order to better understand phyllotactic patterns we should first consider the role of auxin, a plant growth hormone that is often responsible for these changes. Auxin triggers the elongation of plant cells and is involved in regulating plant growth. It is usually synthesised in the apex (tip) of plant stems. Auxin can be transported in the phloem using a protein called the PIN1 Auxin efflux carrier (some of it also makes it's way cross cell membranes too, but this process is a bit slower). The phloem moves PIN1-auxin in all directions up and down the plant. This is important because root growth is stimulated and regulated by auxin, and a cut stem will require new roots in order to survive. As concentrations of auxin change in the apex of the shoot, they can vary across the plant cellular tissue. This can trigger the peripheral zone (shown in red below) to develop slightly different leaf formations because the primordia (bundle of plant cells that decide what organ to create, growing within the peripheral zone) ends up in a slightly different configuration (usually the 137.5° "golden" angle, but not always). As the primordia matures, the new leaf emerges and you can end up going from a whorl to a spiral, visa versa, or even something in-between.
1653371531507.png

But that isn't quite the end to the story. Phyllotactic pattern "shifts" can also be triggered by genetic mutations and we call this a "variation". These variations can look exactly the same as a change bought on by auxin. They are said to: fluctuate, transition, or result in longer-term permutations. As you would expect with genetics, the variation can be very species, population, and individual-specific, and this is most plausible with Rotala wallichii, but there have been generic genes identified. One of your stems could have mutated, or it's genetics could have been triggered to produce this response (with no genetic mutation). Some plants also adapt to changing environmental conditions and undergo phyllotactic pattern shifts (such as submersion or emergence) and we see that a lot in different Rotalas. So in answer to your questions, there are multiple triggers and lots of randomness. Here are the two main patterns. The green blobs below represent leaf primordia and leaf "organs" being spaced differently:
1653373821217.png
 
Yes I have. It's called a shift in the phyllotactic pattern and it is rather common.
Phyllotaxy describes the arrangement of leaves around a stem. Commonly this can be spiral or whorled, and that is what you are observing.

In order to better understand phyllotactic patterns we should first consider the role of auxin, a plant growth hormone that is often responsible for these changes. Auxin triggers the elongation of plant cells and is involved in regulating plant growth. It is usually synthesised in the apex (tip) of plant stems. Auxin can be transported in the phloem using a protein called the PIN1 Auxin efflux carrier (some of it also makes it's way cross cell membranes too, but this process is a bit slower). The phloem moves PIN1-auxin in all directions up and down the plant. This is important because root growth is stimulated and regulated by auxin, and a cut stem will require new roots in order to survive. As concentrations of auxin change in the apex of the shoot, they can vary across the plant cellular tissue. This can trigger the peripheral zone (shown in red below) to develop slightly different leaf formations because the primordia (bundle of plant cells that decide what organ to create, growing within the peripheral zone) ends up in a slightly different configuration (usually the 137.5° "golden" angle, but not always). As the primordia matures, the new leaf emerges and you can end up going from a whorl to a spiral, visa versa, or even something in-between.
View attachment 189045
But that isn't quite the end to the story. Phyllotactic pattern "shifts" can also be triggered by genetic mutations and we call this a "variation". These variations can look exactly the same as a change bought on by auxin. They are said to: fluctuate, transition, or result in longer-term permutations. As you would expect with genetics, the variation can be very species, population, and individual-specific, and this is most plausible with Rotala wallichii, but there have been generic genes identified. One of your stems could have mutated, or it's genetics could have been triggered to produce this response (with no genetic mutation). Some plants also adapt to changing environmental conditions and undergo phyllotactic pattern shifts (such as submersion or emergence) and we see that a lot in different Rotalas. So in answer to your questions, there are multiple triggers and lots of randomness. Here are the two main patterns. The green blobs below represent leaf primordia and leaf "organs" being spaced differently:
View attachment 189048
Thank you for the detailed explanation!

So in theory, if the growth on the tip of the stem plant receives Auxin at varying levels, it can create this new growth pattern? Are some plants predisposed to moving different levels of Auxin to parts of the structure as a evolutionary advantage for growth?

If I cut the whorly stem to propagate new growing tips, the new daughter plant structure may or may not revert back to their original growth pattern, depending on if the trigger that started the shift in phyllotactic pattern was there or not.

Excuse my ignorance on the science of this particular subject.
 
So in theory, if the growth on the tip of the stem plant receives Auxin at varying levels, it can create this new growth pattern? Are some plants predisposed to moving different levels of Auxin to parts of the structure as a evolutionary advantage for growth?
Yes that is exactly right. In certain species that exhibited undesirable floral phyllotaxy, like in tomatoes that did not fruit, some extra auxin was added to just the apex (the growing tip) and this caused the desired pattern to be re-established, and they got the tomatoes back. This is largely how we know that auxin concentrations in the apex (the peripheral zone) are important to a lot of species. As you say, this is not always the case because some species are genetically-predisposed, there are other environmental factors, and there can be a mutation, etc. There is also considerable evolutionary diversity with how auxins are managed by different plants, like you mention. We can expect many plants to actively manage auxin to advantage their growth, as you put it.

To make matters even more complex, both the roots and the growing tips are dependent upon auxin, and if you cut and release auxin into the aquarium water column, then firstly you will loose some auxin from the plant phloem, and secondly, auxin will enter into the water column and potentially be reabsorbed by the plants, meaning that the concentrations could be less likely to remain stable in the fist place. Auxin is a commonly called a "stress response" hormone, so it is not unimaginable to think that the changes could be induced by cutting and replanting. But there are so many strong variables, this is complete conjecture on my part, and is very much on the dark side of the moon in terms of what people actually believe.

Auxin moves in a complex with PIN1 proteins when it leaves the source cell (auxin efflux) and will travel through both plant cellular tissue and through vascular tissue (notably the phloem). It seems to do this due to polarity and pH gradients within the plant. Unfortunately, it only gets more complex and we have to looks at some very immersive biochemistry to understand this fully. But this webpage has a fairly simple description that might help if somebody was interested. The best way to look at it is through the chemiosomotic model, developed by some very forward-thinking individuals. But ultimately, you don't need to know any of this really.

If I cut the whorly stem to propagate new growing tips, the new daughter plant structure may or may not revert back to their original growth pattern, depending on if the trigger that started the shift in phyllotactic pattern was there or not.
Exactly right again! It is also rather possible that this could have been triggered due to environmental conditions like high light and air exchange levels, because I faintly remember that R wallichii can have a spiralling phyllotactic pattern when emergent and terrestrial. There is absolutely no certainty that I know what is going on or what could happen. Many scientists are still chipping away at these topics. There is overwhelming uncertainty unless the species has been studied before.
 
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Yes that is exactly right. In certain species that exhibited undesirable floral phyllotaxy, like in tomatoes that did not fruit, some extra auxin was added to just the apex (the growing tip) and this caused the desired pattern to be re-established, and they got the tomatoes back. This is largely how we know that auxin concentrations in the apex (the peripheral zone) are important to a lot of species. As you say, this is not always the case because some species are genetically-predisposed, there are other environmental factors, and there can be a mutation, etc. There is also considerable evolutionary diversity with how auxins are managed by different plants, like you mention. We can expect many plants to actively manage auxin to advantage their growth, as you put it.

To make matters even more complex, both the roots and the growing tips are dependent upon auxin, and if you cut and release auxin into the aquarium water column, then firstly you will loose some auxin from the plant phloem, and secondly, auxin will enter into the water column and potentially be reabsorbed by the plants, meaning that the concentrations could be less likely to remain stable in the fist place. Auxin is a commonly called a "stress response" hormone, so it is not unimaginable to think that the changes could be induced by cutting and replanting. But there are so many strong variables, this is complete conjecture on my part, and is very much on the dark side of the moon in terms of what people actually believe.

Auxin moves in a complex with PIN1 proteins when it leaves the source cell (auxin efflux) and will travel both through both plant cellular tissue and through vascular tissue (notably the phloem). It seems to do this due to polarity and pH gradients within the plant. Unfortunately, it only gets more complex and we have to looks at some very immersive biochemistry to understand this fully. But this webpage has a fairly simple description that might help if somebody was interested. The best way to look at it is through the chemiosomotic model, developed by some very forward-thinking individuals. But ultimately, you don't need to know any of this really.


Exactly right again! It is also rather possible that this could have been triggered due to environmental conditions like high light and air exchange levels, because I faintly remember that R wallichii can have a spiralling phyllotactic pattern when emergent and terrestrial. There is absolutely no certainty that I know what is going on or what could happen. Many scientists are still chipping away at these topics. There is overwhelming uncertainty unless the species has been studied before.
Thank you for the explanation and reply! There's so much information to absorb here that it's a bit overwhelming.

So on a hobbiest level, there really isn't a black and white way to tell if a plant will change its phyllotactic pattern. Especially in a submersed, closed system where chemicals/hormones can accumulate without being removed naturally like in a natural system. All this information is so intriguing, are you a plant biologist by profession?
 
I’ve also observed it.

I wouldn’t be surprised if the motivation for the plant to adapt is to moderate light intake and gas exchange as @Simon Cole suggests with the terrestrial observation.

One form is dancing and makes us feel more harmonious.

Notice light and flow availability when it twirls. Turn your light down and it won’t twirl I reckon.

It’s bathing in light and co2 and I bet the organ orientation could be correlated to facilitate that acquisition. Throw it in inert substrate and poorly managed column dosing - it will look strained.

Lovely post. Thanks for it.
 
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I’ve also observed it.

I wouldn’t be surprised if the motivation for the plant to adapt is to moderate light intake and gas exchange as @Simon Cole suggests with the terrestrial observation.

One form is dancing and makes us feel more harmonious.

Notice light and flow availability when it twirls. Turn your light down and it won’t twirl I reckon.

It’s bathing in light and co2 and I bet the organ orientation could be correlated to facilitate that acquisition. Throw it in inert substrate and poorly managed column dosing - it will look strained.

Lovely post. Thanks for it.
I think you're definetly right. This plant in particular is probably regulating the nutrient, light, and Co2 in the most effecient way possible by growing in a spiral formation with the flow available. It's amazing how plants can adapt in surprising ways. I have noticed though that only 1 of my stems have this growth pattern and the others in the same area of the tank still grow with normal nodes.
 
I think you're definetly right. This plant in particular is probably regulating the nutrient, light, and Co2 in the most effecient way possible by growing in a spiral formation with the flow available. It's amazing how plants can adapt in surprising ways. I have noticed though that only 1 of my stems have this growth pattern and the others in the same area of the tank still grow with normal nodes.
Please post more photos.

I’d love to extrapolate based on the species type.
 
I have noticed though that only 1 of my stems have this growth pattern and the others in the same area of the tank still grow with normal nodes.
Flow and light availability can vary immensely even by a few cms in my experience.

Nutrients not as much - for localized areas of same species … for different species though, yes.
 
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