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Full version of the question: How would a plant adapted to living at -23 degrees Celsius keep the water vapor it transpirates from flash freezing to the surface of/within its leaves and clogging its stomata? (It was over 150 characters.)

So, this is partially inspired by this question:

I want a layer out of frozen clouds floating around my planet. How could that work?

And it got me thinking - at the altitude of cirrus clouds, 6000 meters, the air is between -22.6 and -24.6 degrees Celsius. The clouds are formed by flash freezing water vapor. There are plenty of possibilities for modifying plants so their xylem can carry water that high, and how to do it without freezing the xylem, but I want to zoom in and focus solely on another part of the plant - the little stomata releasing water vapor into the air.

https://en.wikipedia.org/wiki/Stoma

If a stoma is releasing water vapor into the air, and the vapor flash freezes, then how would the plant prevent ice from forming around the edges of the stoma until it's clogged?

If the plant uses an antifreeze like turpentine, and removes the antifreeze from solution just before the water vapor is released, how would it prevent the water from freezing just below the surface of the leaf, just before a stoma's opening?

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  • $\begingroup$ It's a nice question, but last sentence makes it a candidate to being closed as too broad. One question per question, please, and when you think you have it all figured out, you can ask reality-check question to test it once more. $\endgroup$ – Mołot Apr 5 '18 at 7:31
  • $\begingroup$ Duly noted and edited. Fixed? $\endgroup$ – KernelOfChaos Apr 5 '18 at 7:46
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    $\begingroup$ There's a protein called thermogenin that produces heat from ATP. you can use it to heat the leaf surface and keep it water-free $\endgroup$ – SilverCookies Apr 5 '18 at 7:49
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    $\begingroup$ @SilverCookies If you could expand that into an answer, I'd love to upvote it. $\endgroup$ – KernelOfChaos Apr 5 '18 at 7:53
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    $\begingroup$ What's the windspeed at that altitude? It may be the case that ANY water (solid, liquid, or gas) is easily removed from the plant because it gets blown away. Combine this with @L.Dutch's answer about cactus-like adaptations: Ice won't accumulate on a waxy surface in a strong wind. $\endgroup$ – dwizum Apr 5 '18 at 12:55
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It can use the same trick used by Cactus: limit as much as possible water exchanges to the outside.

Temperature aside, a place with -23 C is also a dry desert: liquid water is pretty scarce, and the plant has all the interest not to waste it.

Reduce the stomae size, have the leaf surface covered with a wax like substance, reduce the size of the leaves. All this adaptations will reduce the amount of water lost to the outside and therefore the related risk of flash freezing.

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The stomata are essentially entryways to the cavities inside a plant-leaf that are used to circulate air, and thereby get rid of water and import CO2 to the centers of photosynthesis - they are as small to minimize unwanted ingress end egress and be easily closeable.

One could imagine a plant that has ever-expanding cavities, instead of the bottleneck created by stomata, and thereby could just get rid of ice by not letting it adhere (surface molecules with appropriate tension), shaking it offf whenever the plant is moved by wind or vibrations.

Also, stomata are not necessary when the leaf ist sufficiently thin (this is effectively an adjunct to the above possibility) as the diffusion of water and gases is not hindered that much, then.

If the stomata have, for some reason, to be there, the production of ice could be steered: look up hair ice (https://en.wikipedia.org/wiki/Hair_ice) - The ice could be of some structural use (as a sort of skeleton) or simply be forced to grow out at the side(s) of the stomata.

Hindering the accretion of ice would be possible by heat (most biochemical processes will have heat as a loss, some are even tailored to release heat) - which is costly, or by chemicals (if the process of water diffusion is not altered, every molecule of water would need a companion - very costly) - or you stop the outgassing of water by mixing it with a substance that will coat it, but then you have to get rid of droplets of water.

I'd go with the hair-ice.

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I was just answering an old question about hydrogen peroxide life, that might give a hint: use an eutectic mixture of water and hydrogen peroxide. The mixture has a freezing point of -56.5 C, which is more than enough. The main reference I used may have more useful material for this particular plant application - the hygroscopicity of the mixture might be a mixed blessing.

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Option 1 chemistry

The plants could secrete a ice formation inhibitor. there is already existing life that produce chemicals that prevent ice crystals from forming. Combine one of these chemical with the fact that stomata flex and contract and any ice will be cleared regularly before it has a chance to clog the stomata.

Option 2 heat

The plant is endothermic and keeps itself warm enough to prevent freezing, there are already endothermic plants, the dead-horse arum (named for its smell) is one of the most efficient heat producers in nature. The skunk cabbage is one of the most well regulated maintaining a 30-36 degree temprature in condition most mammals could not manage. to do this constantly you might want to make the plant look more like a cactus to minimize surface area.

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Your problem applies to the entire plant, not just the stomata. You need the sap to not freeze in that environment.

Plants already produce ethanol or methanol under environmental stresses (concurrent absence of light for photosynthesis and low oxygen). Your plant can incorporate it into its normal metabolic processes, killing two birds with one stone.

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