How do trees cope with winter??

[john87]

Hi All,

Was just wondering how do trees cope with cold???

I would have thought that the water in them would freeze and kill them?? How does a tree avoid this??

 

john..

[Doug Tait]

I'm a little vague on the subject John but I think it's to do with starch being converted to sugars triggered by lower light levels, the concentrated sugar acts as an antifreeze.

Prepared to be told I'm wrong by anyone that actually knows...

[Steven P]

The also take everything out out the leaves that are useful and shed them - smaller surface area to get cold - or they have fat round spikey leaves (generally) with a smaller surface area to the volume.

 

They shut down a lot, don't need so much water in the trunk (see the leaves which lose a lot of water) again helping (chop a tree down in winter, it will be drier than one cut in the summer)

 

After that the memory fades from school lessons many many years ago

[Steven P]

26 minutes ago, Doug Tait said:

I'm a little vague on the subject John but I think it's to do with starch being converted to sugars triggered by lower light levels, the concentrated sugar acts as an antifreeze.

Prepared to be told I'm wrong by anyone that actually knows...

 

Maple trees need a certain conditions to get good sugary sap - think also has to do with temperature at certain times of the year as well

[openspaceman]

37 minutes ago, Doug Tait said:

I'm a little vague on the subject John but I think it's to do with starch being converted to sugars triggered by lower light levels, the concentrated sugar acts as an antifreeze.

Prepared to be told I'm wrong by anyone that actually knows...

The cell water becomes a more concentrated solution of salts as water is withdrawn in the autumn, this more concentrated solution has a lower freezing point plus I suspect the cells become plasmolised so if they did freeze the increased volume would not rupture the cell wall.

[manco]

i think some move to southern europe for the winter and come back in spring

[Doug Tait]

Only the soft woods, the proper hard ones stay here and tough it out

[john87]

Yes, anything PURE would solidify at a higher temperature than would a solution, even molton metals do this..

 

So, for an example, an alloy of tin and lead, [as in solder] solidifies at a lower temperature than would either pure lead or tin..

This is because the crystals of whatever it may be, need something to nucleate about..

 

So, yes, the dissolved sugars or whatever, would indeed act as an antifreeze...

 

Apparently, if you take distilled water and cool it, you can go some way beyond the freezing point and nothing happens. You drop in a single grain of salt or whatever the the whole lot will suddenly set solid in front of your eyes.. [in theory at least!!]

 

john..

[daltontrees]

What plants have to avoid is freezing of water within cells. This is extremely damaging.

 

Depending on species, they may try to avoid low temperatures by staying warm. Aspen, for example, still metabolises internally at less than -10C. 

If that's not enough, they avoid freezing by antifeeze compounds (carbohydrates, sugars, alcohols, salts) in the cells and sap. This works down to -10C.

In the reall tough plants, the cells hold only pure water, which can supercool without freezing down to -40C. In the really really tough plants anything outside the cells can freeze but the cell walls are tough enough to withstand the pressure of ice growth around them. This has been documented down to -200C.

[john87]

I found a video that expalins about the nucleation needed for crystals to form and also about starting nucleation by banging the water. This is the reason that it is difficult to do this, the vibration of the fridge is enough, it is a better job if you can get the water to freeze just by standing it outdoors..

 

See!!!! my hours in tech doing materials technology were not entirely wasted!!

 

john..

supercooled+water - Recherche Google

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