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When temperatures plummet still further, more defence systems are required. Scientists have discovered that some, such as winter cabbages, produce proteins that restrict the movement of water out of the cells, preventing dehydration. Antifreeze proteins in other species lower the temperature at which water freezes or limit the growth of ice crystals between the cells. Recent research has identified a protein that allows cells to continue to function even when severely dehydrated.
From the mighty oak to summer-flowering phlox, hardy plants have evolved winter survival techniques so sophisticated that scientists are still trying to understand exactly how they work.
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Snow can be less harmful to plants than heavy frost because it acts as an insulating blanket - preventing soil temperatures falling below 0°C (32°F). However, heavy snow causes physical damage, breaking off branches and exposing inner parts of trees and shrubs to disease and cold. For this reason, it is advisable to trim hedges into an 'A' shape to help them shed a heavy load. Ground-hugging alpines, such as saxifrage, can easily bear the weight of snow above them. They also use heat radiating from the surrounding soil and rocks to survive severe winter temperatures. A cloche protects fragile plants from being flattened by snow and also creates a warm pocket of air. |
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Roots and bulbs tend to be less resistant to the cold and frost than stems and leaves, but this is because many don't need to be. Soil temperatures remain higher than the air temperature in winter and offer protection for plants whose upper parts die down. Hardy bulbs, tubers and roots systems act as storage organs for food and water and keep the plant alive during the colder months. The food inside them also acts as an antifreeze, protecting them from the harmful effects of frost.
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