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# 1.2.2 The cellular level

The water in plant and animal tissues has two major components: the intracellular fluid (within cells) and the extracellular fluid, which fills the spaces between cells. When a tissue freezes, ice typically forms first in the extracellular fluid. Ice formation has two harmful effects:

1. It disrupts cell walls and cellular membranes.

2. The formation of ice in extracellular fluid effectively removes water from solution, thereby increasing its solute concentration. The gradient in solute concentration between the extracellular fluid and the cells it surrounds causes water to move out of the cells into the extracellular spaces (a process called osmosis), so that the cells collapse.

The destructive effect of frost on plants is a familiar consequence of these forms of cellular dysfunction. Frosted foliage collapses and turns brown, a result of the destruction of tissues in which ice has formed. These effects are especially obvious in some non-native plants, which are not adapted to survive frost.

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OpenLearn - Surviving the winter
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