The Full Wiki

Xerophyte: Wikis

Advertisements
  

Note: Many of our articles have direct quotes from sources you can cite, within the Wikipedia article! This article doesn't yet, but we're working on it! See more info or our list of citable articles.

Encyclopedia

From Wikipedia, the free encyclopedia

A xerophyte or xerophytic organism (xero meaning dry, phyte meaning plant) is a plant which is able to survive in an environment with little available water or moisture, usually in environments where potential evapotranspiration exceeds precipitation for all or part of the growing season. Plants like the cacti and other succulents are typically found in deserts where low rainfall amounts are the norm, but xerophytes such as the bromeliads can also be found in moist habitats such as tropical forests, exploiting niches where water supplies are limited or too intermittent for mesophytic plants. Plants that live under arctic conditions may also have a need for xerophytic adaptations, as water is unavailable for uptake when the ground is frozen. Their leaves are covered with silvery hairs (creates wind break & light reflective surface).

Adaptations of xerophytes include reduced permeability of the epidermal layer, stomata and cuticle to maintain optimal amounts of water in the tissues by reducing transpiration, adaptations of the root system to acquire water from deep underground sources or directly from humid atmospheres (as in epiphytic orchids), and succulence, or storage of water in swollen stems, leaves or root tissues. The typical morphological consequences of these adaptations are collectively called xeromorphisms.

Contents

Mechanism table

Mechanism Adaptation Example
Limit water loss waxy stomata prickly pear
few stomata
sunken stomata pine
stomata open at night tea plant
CAM photosynthesis cactus
large hairs on surface Bromeliads
curled leaves esparto grass
Storage of water succulent leaves Bryophyllum
succulent Plant stem Euphorbia
fleshy tuber Raphionacme
Water uptake deep root system Acacia,"prosopis"
below water table Nerium oleander
absorbing surface moisture from leaf hairs or trichomes Tillandsia

Importance of water conservation

If the water potential inside the leaf is higher than outside the leaf, the water vapour will diffuse out of the leaf down this gradient. This loss of water vapour from the leaves is called transpiration, and the water vapour diffuses through open stomata in the leaf. Although this is a normal and important process in all plants, it is vital that plants living in dry conditions have adaptations that decrease this water potential gradient, and decrease the size of open stomata, in order to reduce water loss from the plant. It is important for a plant living in these conditions to conserve water because without enough water, plant cells lose turgor and the plant tissue wilts. If the plant loses too much water, it will pass its permanent wilting point, where the plant will die.

Types of xerophytic plants are:

  • Succulent plants - typically store water in stems or leaves. They include the Cactaceae family which typically have stems that are round and store a lot of water. Often, as in cacti where the leaves are reduced to spines, their leaves are vestigial, or they do not have leaves.
  • Bulbs - water is stored in their bulbs, at or below ground level. They may spend a period of dormancy during drought conditions underground, and are therefore 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.

External links

See also

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.  
Advertisements

Simple English

[[File:|thumb|220px|A xerophyte species Euphorbia virosa]]

Xerophytes are plants are plants which are adapted to dry/desert areas. To survive these harsh conditions they have special features.[1] For example, a cactus has white hairs which help to prevent water loss. Another example are Manzanita plants, which have a thick waxy coating and keep their leaves vertical to the sun.

Adaptions

Some Xerophytic plants sit out a drought. They can still extract water from soil. They may have very salty cell sap and therefore a very low water potential in the roots; they may have very extensive or deep roots or may pick up the slightest dew and survive on that).

Others have special features about their shape or structure (xeromorphs). Thick waxy cuticle (Aloe); hairy surfaces (Edelweiss); dense packing of leaves, reduced leaf size (Cupressus); reduced density of stomata (Cactus); pitted and grooved position of stomata (Ammophila) Water storage in stem and tubers, etc. (Baobab). They may also protect this water store from animals by spines and chemicals.

Mechanism table

Mechanism Adaptation Example
Limit water loss waxy stomata prickly pear
few stomata
sunken stomata pine
stomata open at night tea plant
CAM photosynthesis provides CO2 during day when stomata are closed cactus
large hairs on surface Bromeliads
curled leaves esparto grass
Storage of water succulent leaves Kalanchoe
succulent Plant stem Euphorbia
fleshy tuber Raphionacme
Water uptake deep root system Acacia, Prosopis
below water table Nerium oleander
absorbing surface moisture from leaf hairs or trichomes Tillandsia

References

  1. Taylor D.J; N.P.O. Green & G.W. Stout 2001. Biological Science 1 & 2, 3rd edition. Cambridge University Press. ISBN 0-521-56178-7.


Advertisements






Got something to say? Make a comment.
Your name
Your email address
Message