Xerophyte

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A xerophyte is an organism that has adaptations to enable it to get through, or even thrive, in areas with very little free moisture. Xerophytes occur in all kind of environments, including some where water is present. Cacti and other succulents are typically found in deserts while bromeliads can be found in sun 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.

The adaptations are multiple. They may aim to limit water loss (including water loss through stomata), but also to obtain as much water as is possible from the soil. They are summarised in the table below.

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

Types of xerophytic plants are:

• Succulent plants - they typically store energy in stems or leaves. They also include 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.
• Bulbs - 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.
• Short-lived annuals 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.

[edit] 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.