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XEROPHYTE

A xerophyte describes a plant that has structural (xeromorphic) and physiological adaptations which enable them to survive, or even thrive, in areas with very little free moisture. Xerophytes occur in all kind of environments, not simply those which immediately appear free of water such as deserts. Cacti and other succulents are typically found in deserts while bromeliads can be found in rain forests. Plants that live under arctic conditions may also have a need for xerophytic adaptations as water is not available for plant uptake when it is frozen. Many countries have xerophytes, including those which are wet such as the United Kingdom in sand dunes and sea shore strand lines.

The adaptations are several, primarily these aim to limit water loss (including water storage), but also to obtain as much water as is possible from the environment. They are summarised in the table below.

Mechanism Adaptation Example
Limit water loss waxy cuticle prickly pear
few stomata
sunken stomata pine
stomata open at night ice plant
fine hairs on surface
curled leaves marram grass
Storage of water succulent leaves Bryophyllum
succulent stems candle plant
fleshy tuber Raphionacme
Water uptake deep root system acacia
below water table oleander
laterally extensive, shallow root system cactus
absorbing surface moisture from leaf structures called trichomes Tillandsia

Types of xerophytic plants are:

  • Succulent plants - they typically store moisture in their stems or leaves. They also include cacti from the Cactaceae family which typically have stems that are round and store a lot of water. Often their leaves are vestigial, or they do not have leaves. These are known as drought endurers.
  • Bulbs, seeds and spores - water is stored in their bulbs, at or below ground. They may spend a period of dormancy during drought conditions underground, these are known as drought evaders. They can often germinate following rainfall. An example of this is the California poppy whose seeds lie dormant during drought and then, flower and form seeds within four weeks of rainfall.

References

  • D. J. Taylor, N. P. O. Green, G. W. Stout (2001). Biological Science 1 & 2, third edition. Cambridge University Press. ISBN 0-521-56178-7.