xer-, xero-, xir-
2. The inability of a plant or animal to survive in dry places.
In biology, a xerophobia is an aversion to arid habitats by animals, or an inability of certain plants to survive in such moistureless locations.2. The inhibition of salivary flow resulting in a dry mouth: Such xerophobias are caused by emotional conditions, such as fear, anger, or excessive excitement.
2. A dry and thickened condition of the conjunctiva, sometimes following chronic conjunctivitis, disease of the lacrimal apparatus, or vitamin-A deficiency.
2. A plant that is adapted to an arid or dry environment.
A xerophilous plant and a plant that is structurally adapted for growth with a limited water supply.
The term is generally applied not only to actual desert plants, but also to those inhabiting salt marshes or alkaline soil or bogs, where water absorption is slow or difficult because of the excess of salts or acids in solution.
Xerophytes exhibit many modifications of structure which limit transpiration (breathing), because of a thickened epidermis, waxy or resinous coatings, dense pubescence, copious aqueous tissue, etc.
Many xerophytes have developed specialized tissues (usually nonphotosynthetic parenchyma cells) for storing water, as in the stems of cacti and the leaves of succulents. Others have thin, narrow leaves, or even spines, for minimizing water loss.
Xerophyte leaves often have abundant stomata to maximize gas exchange during periods in which water is available, and the stomata are recessed in depressions, which are covered with fine hairs to help trap moisture in the air.
Heath plants grow in tracts of uncultivated, open land with infertile, often sandy soil covered with rough grasses and small bushes or heather; a low-growing Eurasian shrub (Calluna vulgaris) growing in dense masses and having small evergreen leaves and clusters of small, bell-shaped pinkish-purple flowers.
A powdered surface of an electrically charged selenium plate records the roentgen image.
2. An ecological succession commencing on a dry-rock surface.
2. The abnormal dryness of the skin, mucous membranes, or conjunctiva.