Overwintering is not an easy task for any kind of creature because our cells don't survive the cold very well. And those animals that live in the cold have various ways of surviving the cold. For example, bears can hibernate; seals have a lot of blubber; and humans can keep out the cold by finding shelter and wearing clothes and shoes. But plants that grow in cold climates also need a variety of methods to survive the winter.
If the temperature drops low enough, even the most hardy trees freeze and cells die. So how do trees survive sub-zero temperatures? While the subterranean part of the tree is kept relatively warm by being insulated by a layer of snow, the bare parts of the tree are not protected in any way.
What causes trees to become particularly frost-resistant in winter? It turns out that this frost-resistant skill of trees has evolved over tens of millions of years. In order to adapt to changes in their surroundings, they use the method of "sleeping" each year to cope with the cold winter. We know that the growth of trees consumes nutrients, and trees grow rapidly in spring and summer, and the depletion of nutrients exceeds the accumulation, so the ability to protect against freezing is also weak. But in autumn and winter, things are different. At this time, the temperature is high during the day, the sunshine is strong, the photosynthesis of the leaves is strong, and the temperature is low at night, the tree grows slowly, the nutrient consumption is less, and the accumulation is a lot, so the longer the tree, the more fat storage. Small branches became big trees, and gradually the trees began to have a strong ability to resist the cold.
Many plants die each winter and grow back in spring. But the tree is too big to regrow every year. Besides sleeping, they have other strange ways to survive the winter. In some cases, for example, they turn themselves into a glassy state. This happens when the water temperature in the tree cells drops below freezing. Once the tree cells are in a glassy state, it doesn't matter how cold the outside environment is, because the cells are already in a state of being protected from harm.
To survive cold winters, trees begin preparing for "cold adaptation" in late summer, which involves a series of physiological changes in leaves, stems, and roots. Starch that accumulates in trees in the fall is converted into sugar and some even fat in winter. These are cold-proof substances that prevent cells from freezing. If you take the sliced tissue of the tree and look at it under the microscope, you will also find an interesting phenomenon! The cells that are usually connected to each other are broken in winter, and the cell walls and protoplasm also leave. Small changes invisible to the naked eye have a huge impact on a plant's frost resistance, and when the tissue freezes, it eschews the most important part of the cell, the protoplasm, which is immune to intercellular freezing, ensuring the tree's foundation for life.