How to Survive in Winter?

April 22, 2021 0 Comments

 Living through a cold winter is not easy for any of us living things are cells just don't do well in the freezing cold animals that live in cold climates have all kinds of adaptations to keep themselves alive when it's freezing bears hibernate seals have plenty of blubber humans seek shelter and wear clothing and shoes but plants in cold climates also need ways to get themselves through the winter and they don't really have the option of blubber or shoes for that matter many plants. Just die every winter and regrow within the spring.

But trees are too big to regrow per annum . So to urge themselves to Spring they need other stranger adaptations including in some cases turning themselves into glass the matter begins when the temperature Falls below the freezing point of water in a tree's cells which normally happens at 0 degrees Celsius water expands when it freezes and if that's allowed to happen inside a cell ice crystals can Pierce through the cell's membranes, which isn't great. In fact, it kills the cell luckily for trees ice only forms inside their cells when the temperature drops below freezing. Very suddenly when it falls more gradually, which is what usually happens as winter approaches ice tends to make within the spaces between the cells during a process called extracellular freezing as the temperature slowly Falls ice forms on the outside of a tree's cell walls before the inside of the cell gets cold enough to freeze then once there's some ice between the cells the water inside the cells does something weird.

It flows outward toward the ice that movement is because of a property known as chemical potential as a general rule substances move from a areas with higher chemical potential to areas with lower chemical potential and because of the way it's molecules are arranged ice has a lower chemical potential than liquid inside the cell. So the water inside the cell moves towards the ice outside the cell and freezes there instead of freezing inside the cell and destroying great problem solved except there's more to surviving within the winter than simply keeping your cells from rupturing. I mean pretty much all plants undergo extracellular freezing weather they're cold tolerant or not, but not all of them survive the process see the water moving out of the cell. It causes another problem dehydration dehydration is bad for all kinds of reasons, but for trees the main danger is that as a cell shrinks from water loss. It's so membranes can move close enough together to react that can tear the membranes apart and is generally just not a good idea. So trees that are good at surviving cold temperatures have an entire bunch of various strategies to avoid this dehydration problem. One of the foremost common techniques they use is named supercooling.

That's what happens when the water falls below the temperature where it would normally freeze but stays liquid. There are a few reasons. Liquid might not freeze it as normal temperature, but for trees sells the thickness of the liquid inside them also known as viscosity is one of the main ones this liquid gets thicker during extracellular freezing as water is drawn from the cell and leaves behind a thicker concentration of dissolved substances. The thicker the liquid the harder it is for ice crystals to begin forming and the more I can be super cool as temperatures fall trees that use super cooling also start producing more of certain molecules like sugars that makes the liquid inside them even thicker you might be familiar with this liquid we call it sap.

Super cooling at trees can avoid getting too dehydrated by extracellular freezing and hold more liquid inside their cells without it freezing into ice the combination of extracellular freezing and supercooling can keep trees alive through temperatures as low as negative 40 degrees celsius, but around negative 40 or negative 50 degrees super cooling backfires at a certain point. It doesn't matter what you are doing to undertake to stay ice crystals from forming.

All the liquid will just spontaneously freeze and if a tree is cells have a bunch of liquid inside them a sudden freeze is very much a death sentence. Luckily for the vast majority of the world's surface. This limit isn't important protection down to negative 40 degrees is more than enough, but that's not true everywhere in some places like in the Arctic normal winter temperatures fall as low as negative 60 degrees Celsius and there are still trees that live there. In fact, there are plenty of trees like the black locust White Pine and Northern White Cedar that can survive being submerged in liquid nitrogen a temperature of negative 196 degrees Celsius and some Is like the Japanese White Birch can survive exposure to liquid helium, which is- 269 degrees Celsius. Not that they'd ever encounter that in the wild but you know, sometimes you've got a tree in a bunch of helium and one thing leads to another anyway, these trees don't survive those temperatures through supercooling instead the insides of their cells become glass a process referred to as vitrification researchers described it as a sort of suspended animation where molecules don't really move normally. Lee I spreads his ice crystals come into contact with other molecules, but if the molecules aren't moving they're not reacting with each other either we don't yet know the exact mechanism that leads to this vitrification but researchers think it's helped Along by a high concentration of sugars in the trees cells along with proteins called the hydrants these proteins seem to bind themselves to the cell's membranes keeping them apart from each other.

Meanwhile other parts of the proteins might get into the sugars within the cell helping arrange them into a glassy State once the trees cells become glass. It doesn't really matter how cold it gets they're essentially