Xerophytes


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Xerophytes

 

plants in dry environments, adapted to withstand heat and drought by means of a number of structural mechanisms. Xerophytes have various ecological and physiological characteristics.

One group of xerophytes, the succulents, has fleshy leaves (agave and aloe) or stems (cacti) and a surface root system. They resist heat, owing to the high viscosity of their protoplasm and the high content of stored water in their cells, but they cannot withstand drought. Another type of xerophyte, the hemixero-phyte, has a root system that reaches ground water. Unable to survive prolonged dehydration of tissues, plants of this type are resistant to droughts, owing to their uninterrupted water supply and intensive transpiration and metabolism. Xerophytes with root systems reaching ground water that grow in the steppes, such as sage, are not able to withstand great heat; those that grow in deserts, such as camel thorn, are heat-tolerant.

Other xerophytes, the euxęrophytes, have a branched but shallow root system (not deeper than 50–60 cm). These plants, which include certain species of wormwood, are pubescent; because their protoplasm is highly elastic and viscous and their metabolism slow, they withstand dehydration and heat well. Another group of xerophytes, the poikiloxerophytes, experiences anabiosis during dehydration, a state in which a plant’s water content is only 2–5 percent and its protoplasm acquires a gelatinous consistency. However, owing to the preservation of balanced respirative activity, the cell organization does not break down to the point of almost complete dehydration. Sometimes other groups of xerophytes are distinguished.

P. A. GENKEL

References in periodicals archive ?
The precise distinctions between xerophytes and sclerophylls are not conspicuous, presumably due to many similar environmental attributes between semi-arid coastal sclerophyllous chaparral and arid continental Mojave Desert shrublands.
That could explain the spread of Chenopodiaceae, Amaranthaceae, Ephedra, Tamarix, and other xerophytes and halophytes.
In conclusion, we can describe the study area by being arid and the type of vegetation by being scanty xerophytes with low speciation throughout the year.
This correspondence is not surprising given the diversity of ecosystems in Marmoucha's territory, ranging from forests of cedar or oak to mountain pastures of xerophytes.
All the recorded species are perennials, xerophytes and mainly dicots, except few species from the monocots.
Such plants are known as xerophytes, a group that also includes plants with deep strong root systems that can grow down to the wet soil of the water table.
minuta were found based on the following parameters: a) the spatial coverage (%) of herbaceous plants, shrubs, xerophytes and aquatic plants; b) the average height of the vegetation (cm); c) the average water depth (cm); d) the substrate type (dry, wet, flooded or underwater; and e) the average distance from a water body (cm) (Figure 1).
According to him, several xerophytes have been introduced in the harsh and arid climates and their potential as horticultural crops lies in the production of fruits that can offer commercial opportunities.
All modern species of Malesherbiaceae are xerophytes, so it is reasonable to assume that the common ancestor was also a xerophyte.
Plants growing in saline environments (halophytes) have higher osmotic pressures than xerophytes living in nonsaline environments, as shown by comparing measurements taken in the Sahara Desert (see table of data).
Nearly the entire peninsula is underlain by porous and fissured limestone with a veneer of soil and xerophytes.