Needled trees shivering to produce enough warmth for evapotranspiration

TheTreeMD

TheTreeMD

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So... I was noticing something interesting. Obviously evergreen species are such because they continue to exudate moisture all winter(talking true "evergreens") I have seen at high altitudes and lower where during freezing temperatures they shiver enough that I wonder whether that plays a role in keeping water moving... obviously very slowly, but... anyone have any more on this?
 
Eventually, the Martian leader and his bodyguards breach the bunker where Dale has been taken and the former reduces Decker to the size of an insect before killing him
 
Very true that moving water freezes at a lower temperature, but that's not really the question here.
No problem in providing the motive force for apoplastic water flow in the winter--evaporation at the substomatal surface. Yes, I know that the stomates are closed, but everything leaks a little. At low relative humidity, the "pulling" force will be at least as great as in summer. Sure, the foliage will lose a lot less moisture in winter...but they are probably acquiring less as well!
Or is someone going to jump out with a "gotcha" here for me! Just trying to help.
 
You're welcome Tom. Nutation, the spiral or oscillatory growth of new shoots and leaf movement was the topic of an 1880 (or thereabouts) book by Robert and Charles Darwin. Yes, the Charles Darwin of the Origin of Species. The topic is one of those classical physiology points that get beaten into students of traditional botany.
 
Ktsmith, that's kind of where I was going with that. It was just something I noticed was that during a slight breeze it forced the needles to move about some... almost like shivering I guess... anyway, my thoughts went to how much the shaking of needles or bending may help the photosynthetic process by preventing water from freezing. Kinds odd I know, but I was noticing a substantial amount of frosting around needle clusters. I realize this is because needles never completely cease gas exchange and evapotranspiration, just wondering if it helps...
 
Thanks TreeMD, that does help. The precise nature of water in living trees still has some mystery to it, although much less mystery than in my student days. Part of the story is that water in the apoplast (the network of cell walls and open cell lumens) isn't necessarily pure water. Xylem water can contain some level of anti-freeze in the form of sugar alcohols and other not readily metabolizable carbohydrates. The water that evaporates is essentially pure and the antifreeze is left behind within the tree, which is good. We do know that water in xylem vessels and tracheids is often in a meta-stable state. If you just took a partially filled capillary tube of water and subjected it to the normally low, negative pressures and ambient temperatures, the water would flash from liquid to vapor. *However* in the living tree, those tubes and capillaries are filled continuously along the full length of root, stem, branch, and if present, leaves. That way, the water can withstand those very negative pressures (which we can call "tension) and still be liquid. Sounds like you are an inquisitive person!
Some of the clusters of ice crystals we see on conifer needles in winter is indeed rime ice which is formed from atmospheric water vapor that immediately condenses as ice crystals on cold surfaces, without forming a perceptible liquid phase. I see that infrequently, but especially in mountains of the northeast. I'm sure it occurs other places as well, but it takes a pretty special set of weather conditions to form.
 
@KTSmith

Is the flashing you speak of the same as sublimation? I’ve seen wet clothes dry from hanging in an outdoor clothesline at subzero air temps in cloudy weather. I’ve know that’s sublimation but the process is a mystery.

Footnote...sublimation popped into my head this week while I was out shopping. I’d forgotten about it until now. It’s time to go read up
 
I read a bit about sublimation. My interest is relative to water. Only. I know what it is but not how clothes can dry at subzero weather but lake ice doesn’t ?????

How it works and why it doesn’t happen all of the time is still unclear
 
KTSmith said:
Thanks TreeMD, that does help. The precise nature of water in living trees still has some mystery to it, although much less mystery than in my student days. Part of the story is that water in the apoplast (the network of cell walls and open cell lumens) isn't necessarily pure water. Xylem water can contain some level of anti-freeze in the form of sugar alcohols and other not readily metabolizable carbohydrates. The water that evaporates is essentially pure and the antifreeze is left behind within the tree, which is good. We do know that water in xylem vessels and tracheids is often in a meta-stable state. If you just took a partially filled capillary tube of water and subjected it to the normally low, negative pressures and ambient temperatures, the water would flash from liquid to vapor. *However* in the living tree, those tubes and capillaries are filled continuously along the full length of root, stem, branch, and if present, leaves. That way, the water can withstand those very negative pressures (which we can call "tension) and still be liquid. Sounds like you are an inquisitive person!
Some of the clusters of ice crystals we see on conifer needles in winter is indeed rime ice which is formed from atmospheric water vapor that immediately condenses as ice crystals on cold surfaces, without forming a perceptible liquid phase. I see that infrequently, but especially in mountains of the northeast. I'm sure it occurs other places as well, but it takes a pretty special set of weather conditions to form.
Click to expand...

Definitely inquisitive. I nearly have a masters in forestry, so I have a pretty good background on morphology, structure and plant/tree processes... just noticed this the other day and it made me wonder. Couldn't find anything so figured I would see what the rest of you all thought. I won't lie, I had been kicking back a beer or two as well.
 
I have read a theory where the movement of leaves, limbs, and trunk can act with some pumping action aiding the movement of water.

The more we learn, we realize the tree is moving water all over the damn place. From root to root, root to leaf, up, down, laterally, dumping it on the dry side of the soil. It's cool as shit!
 
Tom Dunlap said:
I read a bit about sublimation. My interest is relative to water. Only. I know what it is but not how clothes can dry at subzero weather but lake ice doesn’t ?????
How it works and why it doesn’t happen all of the time is still unclear
Click to expand...
Lake ice & snow do sublimate at very cold, and low humidity. (It is just low rate vapor pressure.)
The mass transfer (solid to gas) is very low, and the lake ice mass is high.
Cloths on a line also have a lot of surface area relative to a flat lake.
 
Very interesting topic.
I've always been amazed at the amount of energy change in evaporation and then so transpiration ( thereby perspiration, evaporative cooling).
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Nominal change only in most degree changes.
It takes 1 calorie of heat to increase 1 gram of water 1 degree Celsius
>>very neat and tidy, no leverage, nominal changes only
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Except when changes physical change: solids liquids gas
>>it takes 60 calories to change 1 degree from solid to liquid!
>>like a 60x lever suddenly forward or backwards thru solid liquid change
>>BUT 540 calories to change from liquid to gas 540x leveraged cooling in 1 degree
>>these are stackable 600 calories used to go from solid to gas.
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Change points, as well as slamming thru triple point is temperature and pressure dependant.
>>like altitude affects cook time/temps to same product.
>>air conditioning freon absorbs heat, condenser change pressure to release heat outside.
Fridge same to insulated box, freezer different setting and toaster coil heats to defrost 15 mins day.
High humidity in Florida can mean air too full of water, limiting evaporation, cooling.
But all the same energy manipulation .
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I think energy from state changes, pressure, movements even contractions to maintain positive pressure osmotic on up to make sure no fight to deliver on any pull work in concert to keep slow motion system working even thru worst conditions. Impact of change on evaporation unlike anything else.
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Once water molecule is pulled, whole chain moves with virtually no more effort than 1 molecule evaporating out. Wounds capped off immediately to not break cohesive chain , by air embolism , allowing collapse of chain. Low power system pulling water from 100' down, thru indirect route is totally dependant on cohesion, adhesion in capillaries and positive base pressure for no competition, freely available water on uptake side.
 
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