some important morphological characteristics of xerophytes are :
- The root system is well developed extensive, penetrating very deep. Root hairs and root caps are very well developed.
- The leaves are reduced in area to check transpiration (Casuarina). The leaves may be modified into phyllodes ( Acacia melanoxylon) or succulent (Aloe, Agave, Yucca).
- The leaves show various features like gray or light green coloration, rolling, wilting, leaf fall, leathery glandular out growth, leaf spines, a coating of hairs, wax etc.
- The stems are usually stunted, hard, rigid and covered with thick bark.
- The stems may be modified into phylloclades (Opuntia, Euphorbia) or cladodes (Ruscus, Asparagus).
- The stem may show coating of hairs or wax, or spines etc.
- Where the leaves are absent or caducous, the stem performs the function of photosynthesis (Capparis aphylla).
- The lamina of the leaf may be very much segmented (Acacia, Prosopis) or long, narrow and needle-like (Pinus).
- Some plants have underground stems to tide over the unfavorable conditions (Saccharum).
- Plant habit may be the dwarf, thick or stunted (Aloe, Agave) or prostrate (Euphorbia prostrata).
Examples of Xerophytes
1. Opuntia dillenii (Chittarthor or Nagphani)
It is a shrub found in arid regions. It grows wild as well as can be grown as the hedge plant. It is a succulent xerophyte. The leaves are caducous and fall off in the early stages. The function of photosynthesis has been taken over by the stem in the absence of leaves. Thus, the stem is flattened and green. It looks like succulent leaves. It gives a joined an appearance and each segment is known as a phylloclade. They become thick and fleshy due to the storage of water, which is sufficient for the entire drought period. Phylloclades have shining surface. Plenty of mucilage helps in retaining water.
Each phylloclade bears nodes and aeroles. The axillary branches are modified into spines present in the aeroles. Stiffened hairs called bristles are also present at aeroles . Spines and bristles reduce transpiration and also give protection against grazing. The phylloclades have thick cuticle and sunken stomata.
2. Euphorbia royleana (Danda thor)
It grows wild in the arid areas. It is also cultivated as the hedge plant. It is cactus like shrub showing succulent characteristics. The leaves are caducous, appearing in spring and rainy season but soon fall off. They are succulent, large and thick, The stem is angular, green and bears spines in pairs. It performs the function of photosynthesis throughout the year. The stem is straight and stores a lot of water. The plant secret a white and viscid latex.
3. Aloe barbadensis (Ghikanwar)
It is a wild as well as cultivated shrub showing succulent character. It is cultivated for its medicinal use. The stem is reduced bearing thick and fleshy succulent leaves which store water, The leaves remain crowded and vertically oriented to reduce exposure to sunlight. The leaf surface is smooth and shiny. The margin and apex of the leaf are spiny. The margin and apex of the leaf are spiny to reduce transpiration and protection against grazing. Mucilaginous latex prevents in the plant help retaining water.
It is a cultivated succulent xerophyte. The leaves are modified into scales. The latter are spiny and bear a whorl of axillary branches. The branches are modified into cladodes. Each cladode is a leaflike, needle-shaped and felshy structure of one internode length. Some branches are of unlimited growth and again bear cladodes at each node. During dry conditions, the cladodes also become dry. New shoots arise in every season. The roots are adventitious which store food and water to form root tuber in fascicles.
5. Acacia nilotica (Kikar or Babool)
It is a non-succulent, drought enduring wild tree of arid areas. The root system is extensive taproot system. The stem is thick, erect and covered over by brown corky bark in its older parts. The leaves are compound, stipulate, and bipinnate, Pinnules are small and oval. The stipules are modified into spines to reduce transpiration and prevent grazing from animals.
It is a wild, drought enduring shrub found growing in arid and waste lands. The plant surface is light gray in color and is covered over by a mealy coating Both these features make it possible to absorb less sunlight. The leaves are thick and leathery. There is a covering of wax on the epidermis. The stomata are sunken. The whole plant secret white and viscid latex which helps in retaining water. The latex contains poisonous alkaloids which help in avoiding being grazed by animals. The flowers have a scented smell.
7. Solanum xanthocarpum
It is a wild herb with yellow prickles all over the surface. It is found commonly in dry areas and wastes land. The spines all over the surface reduce transpiration and also provide protection against grazing animals. The plant lies prostrate on the ground. This habit protects it from strong winds. The flowers are bluish purple in color. Fruits are yellow or white streaked with green. The fruit is a berry and bears poisonous alkaloids.
8. Argemone mexicana (Prickly poppy, Jangli post)
It is common, the wild annual herb found in waste lands. The aerial surface bears spines to reduce transpiration and protection against grazing .. Yellow latex present in the plant helps in retaining water. The flowers are yellow and large.
9. Nerium odorum (Kanaer)
It is a small, cultivated tree found in the arid region. The leaves are thick and arranged in whorls.
The surface of the leaf is shining and bears a thick cuticle. The stomata are present on the lower surface of the leaf in varieties bearing a tuft of trichomes or hairs. Young shoots have a mealy coating to reduce transpiration.
10. Zizyphus nummularian (Jangli beri)
It is a non-succulent, drought-enduring wild shrub growing in arid areas or waste lands. The leaves are small, leathery with the hairy or bloomy coating. The stipules are modified into spines. The branches are slender but stiff. The plants are grayish green with dull gray branches.