Cold hardening

Cold hardening is the physiologicaland biochemicalprocess by which an organismprepares for cold weather.

Plants

Image:Plant cell structure.png During the wintermonths as the leaves fall off deciduousspecies and the temperaturedrops, the cold forces watermovement in plantsto stop. Freezing water can cause the cellsin plants to become irreversibly damaged as the water solidifies. To guard against this, plants prepare for winter with a process called cold hardening. Part of this process starts when the cell membranepermeability undergoes a change that permits water to seep into the intracellular voids. In addition, the cells buildup a store of sugars in the protoplasmwhich acts as an antifreezeto prevent cell damage. Even if ice forms outside of the cell, damage to the protoplasm is avoided and the plant can survive an environment even us humans couldn?t without artificial help.

Cold hardening protects plants from chilling injury and freezing injury. Chilling injury occurs at 0-10 degrees Celsius. Symptoms include wilting, water soaking, necrosis (death), chlorosis (yellowing), ion leakage, and decreased growth. Chilling injury is a result of membrane damage, metabolism changes, and toxic buildup. Freezing injury occurs at temperatures below 0 degrees Celsius. Symptoms of extracellular freezing (ice forming outside the cell) include structural damage, dehydration, and necrosis. If intracellular freezing (ice forming inside the cell) occurs, it will lead to death. Freezing injury is a result of lost permeability, plasmolysis, and post-thaw cell bursting.

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Cold+hardening Wikipedia article Cold hardening.