lower critical temperature

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lower critical temperature The minimum body temperature that can be tolerated by an organism. Below this temperature, the biochemical properties of cell structures, especially membranes, are altered, and reactions are slowed such that the organism cannot maintain its usual bodily functions and death may ensue. Also, at subzero temperatures, there is a risk of the body water turning to ice, with consequent physical disruption of cells. The lower critical temperature varies greatly, depending on the `normal' temperature regime to which the organism is adapted. Hence, plants native to warm regions, e.g. maize and cotton, are much more sensitive to chilling than plants from cooler regions. Many animals have strategies for adjusting to seasonal falls in temperature, often entering a state of torpor in which metabolism is greatly reduced. In this state they may tolerate much lower body temperatures than when fully active during the summer months. Compare upper critical temperature.