It is not just hot desert conditions and rapidly draining soils that can exert such pressures. In the tundra, soil water is frozen for long periods and so is unavailable to plants. Plants living at high altitudes and in exposed sites will be subjected to the drying effects of strong winds. Plants growing in these conditions are termed xerophytes. Such plants need to minimize water loss by evaporation.
Many xerophytes have extensive root systems in order to trap available water.
In addition there are other morphological adaptations to reduce the rate of transpiration. Methods of reducing transpiration rate Xerophytic plants may exhibit one or more of the following features. As can be seen from the image left, the inner surface is covered in hairs. The rolled leaf and hairs both serve to trap moist air so reducing transpiration. In addition, a smaller surface area of leaf is exposed to the drying effects of the wind.