Ephedra| Life cycle| Occurrence| Importance
Occurrence
Ephedra is an arid plant. It is found in Europe, Western and Central Asia and Central and South America. It is also found in arid areas of Pakistan. Ephedra is source of drug Ephedrine. It is used for the treatment of asthma, cough and hay-fever.General structure
The plant body of Ephedra is sporophyte. It is a bushy plant. Sometimes, it becomes a climber. It height is ranging from I to 25 feet. The body is divided into root stems and leaves.1. Stem:
Stem and branches are slender and green in colour. It has longitudinal ridges and furrows.
Stem becomes woody due to the limited secondary growth. In some cases, underground rhizomes are also produced. The branches arise from axillary buds. Their arrangement gives the plants characteristic bushy and broom-like appearance. Apical meristem produces nodes and internodes. Meristematic tissues are also present at the base of each internode. Their activity further increases the length of stem. Sometimes, meristematic tissue becomes hard at the end of the growing season. Thus many branches fall. These branches are replaced by axillary shoot. It gives bushy appearance to the plants. The ridges and furrows of the successive internodes alternate with each other.
2. Leaves:
The leaves are scale like. They are opposite and arranged in pairs. The leaves of each pair are joined with each other at their bases. It forms a small sheath around the stem.
3. Roots:
The primary root grows deep in the soil. It develops many secondary roots.
Internal Structure of Stem
The stem has ridges and furrows. So it has a wavy outline in transverse section.1. Epidermis: Stem is covered by heavily cutinized epidermis. The epidermis has stomata. They are present in pits in the region of furrows. A group of sclerenchymatous cells is present below the epidermis in the region of each ridge.
2. Cortex: The cortex is wide. It is formed of parenchymatous cells. These cells have chloroplasts. Thus the cortex of stem is the main photosynthetic tissue of Ephedra. The cells of peripheral region of the cortex are loosely arranged and form palisade layer. The cells in the inner region of the cortex form the spongy tissue.
3. Stele: The central part of the stem is stele. It is surrounded by endodermis. Wide pith is present in the centre of the stele. The vascular bundles are collateral and endarch. They form a ring around the pith. The vascular bundles form a continuous ring due to narrowness of medullary rays. The xylem in Ephedra has true vessels like Angiosperms. Phloem consists of the usual phloem parenchyma and the sieve tubes. But they are without any companion cells. Secondary growth occurs due to the activity of cambium. It produces prominent annual rings.
4. Cork: Phellogen (cork cambium) is produced in the older stem. It forms periderm. The outer tissues of periderm are transformed into the bark.
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