Xerophytes are the plants living in xeric habitats. Soils in these regions have very insignificant amount of water (such condition is called physical dryness). Sometimes water is present in soil but due to some reasons (e.g.: high concentration of salts in water) plants cannot absorb this water (it is called physiological dryness). Reduced humidity in air, fast dry winds, high temperature, high light intensity all contribute to xeric conditions. Plants growing in such regions develop characteristics to tolerate drought. Xerophytes develop the following characteristic features.
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Features
1. Roots are branched, long and penetrate the soil to great depths e.g., the roots of Alfalfa plant maybe 130 feet long. Root of Asparagus are flesly and function for storage of water.
2. In general the leaves are highly reduced to decrease loss of water by transpiration e.g., Casuarina. The petiole is modified into phyllode in some species of Acacia. Agave, Aloe, and Yucca have fleshy leaves. In some plants leaves arc modified into spines e.g., Euphorbia, Opuntia.
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3. Some plants become bulbous and tuberous.
4. In some plants the stem becomes broad and leaf like called phylloclade e.g., Opuntia. In Asparagus cladodes (stem one internode lone) are formed.
5. The dispersal of fruits and seeds takes place when humid conditions are available.
6. Leaves roll forming a tubular structure during dry condition e.g.: Ammophila.
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7. Epidermis is covered with thick cuticle to reduce transpiration.
8. Epidermal cells may have silica crystals.
9. Upper surface of leaf is shining.
10. Epidermis may be multilayered as in Nerium.
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11. Cork is usually formed to check excess loss of water.
12. Waxy coating is present on leaves and stem as in Calotropis.
13. In some plants resin, gum and mucilage is present to reduce loss of water.
14. Velamen is present in the roots of members of Orchidaceae.
15. Sometimes stem, leaves and flowers have hairy coating as in Aerva.
16. Lignified cells are present which provide mechanical support.
17. Presence of sunken stomata covered by hair e.g. Nerium .