Ephedra : Morphology Anatomy and Reproductive Structure | Botany Notes

Ephedra : Morphology Anatomy and Reproductive Structure | Botany Notes

The order Ephedrales includes a monotypic family Ephedraceae, represented by Ephedra. Now have look of Ephedra : Morphology Anatomy and Reproductive Structure | Botany Notes. It is one of the highly evolved groups of gymnosperms. They usually grow in xerophytic habitats.

Systematic Position : Class: Gnetopsida

Order: Ephedrales

Family: Ephedraceae

Genus : Ephedra

Distirbution

Eight species are known from India:

E.intermedia, E.saxatilis, E.gerardiana, E.nebrodensis , E.regeliana , E.pachyclada

• These all are confined to North-West Himalayan region E.foliata occurs in the plains of Rajasthan and Punjab.

ephedra

Sporophyte of Ephedra

Morphology of Ephedra

Most of the species of Ephedra are low growing woody trailing or cIimbing shrubs rarely more than 30cm tall. However, E. trifurca attains a height of 2-3 meters; E. foliata. a climbing species, may reach to a height of 6 meters or more and E. triandra takes the form of a small tree under favourable growth conditions. The sporophyte is differentiated into root, stem and leaves.

Root :

Root is a long tap root in xerophytic species, but in larger form it is replaced by adventitious roots. Roots contain many root hairs, but there is no mycorrhiza

Stem :

•In Ephedra Stem is Green, profusely branched, jointed and is differentiated into distinct Nodes  and Internodes.

•Normally Branches develop in the leaf axils at the nodes.

• The No. of branches = No. of leaves present at the nodes. Internode grows by the meristematic zone present at its base

Leaves

• Leaves are inconspicuous, very minute, scaly and sessile. Arranged in pairs of whorls at the nodes

• Leaves at the nodes are fused  at the base with stem to form sheath. Each leaf has 2 unbrached parallel veins

• True foliage leaves are absent in Ephedra. They do not have the capacity of synthesizing food and the function of photosynthesis is carried by green stem.

Internal structure

Root :

The root is differentiated into epiblema, cortex and vascular region.

Epiblema :  is a single layer of cells. Some cells of epiblema elongate to form root hairs.

Cortex : Cortex is differentiated into an outer and an inner zone. The outer cortex is composed of collenchymatous cells. The inner cortex is parenchymatous. The innermost layer of the cortex forms the endodermis, which is followed by a layer of thin-walled cells, which form the pericycle.

vascular cylinder : of the root may be diarch or triarch. Broad strips of phloem are present in between the arms of xylem.

Stem :

Leaves :

Reproduction

• Most species of Ephedra are mostly dioecious. Though bisporangiate cones may occur in some species such as E.foliata and E. intermedia

Cones occur in groups at the nodes.

• Male and female strobili are compound.They Born in whorls in the axial of scaly leaves at the nodes of branches

Male strobilus

• It Represent  supressed modified lateral branch. Consist of short central axis with 2-10 pairs of opposite decussate bracts.

One or  two basal pairs of bracts are sterile while the others are fertile. A single male flower arise at the axial of fertile bract.

Male strobilus of ephedra

Male Gametophyte and its Development

The microspore is the first cell of the male gametophyte. It is wingless and has a thick exine. The germination of microspore starts within the microsporangium. At the time of germination, the microspore elongates and divides to form a prothallial cell. The second division results in the formation of a second prothallial cell and antheridial initial. The antheridial initial soon divides into a tube cell and a generative cell so then the generative cell soon divides into the nuclei of stalk cell and body cell. Pollens are shed at this five-celled stage.

Female cone

• Arise in whorls of 2-4 and are usually smaller than the male strobili.

Central axis having 2-4 pairs of decussately arranged bracts.

Only upper two bracts have ovule each in their axils.

femALE STROBILUD OF Ephedra

Ovule:

• The ovule remains covered by a cup-shaped outer integument and an inner integument.

• Their outer integument remains attached at the basal portion of the ovule. The inner integument protrudes out in the form of a long tubular micropyle.

• The integuments enclose the nucellus. A small pollen chamber develops near the micropyle in the nucellus.

• Pollen chamber in Ephedra known as the gymnosperms.

•The female gametophyte is centrally located, and the archegonia are present in the female gametophyte near the micropylar end.

Life cycle of Ephedra

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