In this article we will discuss about Ephedra:- 1. Anatomy of Different Parts of Ephedra 2. Reproductive Structures of Ephedra.
Anatomy of Different Parts of Ephedra:
Cut thin transverse sections of internodes of young and old stems, stain them in safranin-fast green combination, mount in glycerine and study.
Stem: T.S. Young Internode:
1. The outline shows many ridges and grooves (Figs. 50, 51).
2. Outermost layer in epidermis with a thick layer of cuticle. Continuity of the epidermis is broken by many sunken stomata present in the grooves.
3. Below the ridges are present the patches of sclerenchyma.
4. Cortex is separated into palisade and spongy parenchyma. Some sclerenchyma patches are also irregularly distributed in the cortex.
5. Vascular bundles are arranged in a ring and the stele is ectophloic siphonostele.
6. Stele is bounded by a layer of endodermis and unilayered pericycle.
7. Each vascular bundle is conjoint, collateral, open and endarch (Fig. 51).
8. In each vascular bundle phloem is present on the outer side and xylem on the inner side and both are separated by cambium.
9. Parenchymatous pith is present at the centre of the stem.
Stem: T.S. Old Internode:
1. It is wavy in outline with ridges and grooves and remains surrounded by a single-layered, heavily cuticularized epidermis. The cortex is also differentiated into palisade and spongy parenchyma (Figs. 52,53).
2. In older stems, the periderm replaces these primary cortical structures.
3. Secondary tissue is externally bounded by a layer of sclerotic cells or stone cells.
4. Cambium cuts secondary phloem towards outer side and secondary xylem towards inner side.
5. Secondary tissue crushes and pushes the primary phloem towards outer side and primary xylem towards inner side.
6. Thin-walled spring wood and thick-walled autumn wood are present in the secondary xylem in the form of regular alternate rings.
7. Sieve tubes and phloem parenchyma are present in phloem.
8. Presence of vessels is the characteristic feature of the wood of Ephedra.
9. Primary medullary rays connect primary phloem and primary xylem while the secondary medullary rays connect secondary phloem and secondary xylem. Medullary rays are uniseriate in young stem while in the old stem these are multiseriate.
10. Resin canals are absent.
11. Parenchymatous pith is present in the centre.
1. Secondary xylem and medullary rays are present (Fig. 54).
2. Tracheids form the major part of secondary xylem.
3. Bordered pits are present on the radial walls of tracheids. They are usually circular and never polygonal in shape.
4. Bordered pits are either arranged in 2 or 3 rows or they are scattered irregularly. Below the bordered pits are also present Bars of Sanio.
5. A few vessels with perforated end walls are also present.
6. Medullary rays are cut lengthwise showing their length and height. They are uniseriate or multiseriate. The height of medullary rays reaches upto 50 cells.
7. In the region of secondary xylem, the medullary rays are made of ray cells and ray tracheids. Bordered pits are present in the tangential walls of ray cells. Ray tracheids are thick-walled and contain bordered pits on their radial and tangential walls.
8. Starch cells surrounded by albuminous cells on both sides constitute the medullary ray in the region of phloem.
1. Tracheids, vessels and medullary rays (Fig. 55) are cut transversely in T.L.S.
2. Bordered pits are observed in the surface view.
3. A small disc torus is present in each bordered pit.
4. The height and breadth of medullary rays can be observed in this plane because they are cut transversely.
5. Simple pits are present on the tangential walls of medullary rays.
Reproductive Parts Ephedra:
1. Ephedra is heterosporous, i.e., two types of spores (microspores and megaspores) are present.
2. Microspores are present in male flowers while the megaspores in female flowers.
3. These flowers are present in the form of cone-like compound strobili.
4. Male flowers are present in the form of male strobilus while many female flowers form the female strobilus.
5. Each strobilus arises on the node in the axil of a scaly leaf.
6. Plant is generally dioecious.
1. Male strobili develop in the axil of scaly leaves on the nodes (Fig. 56).
2. Each strobilus is round or ovoid in shape.
3. In the centre is present the strobilus axis or cone axis.
4. On the strobilus axis are arranged 2 to 12 pairs of bracts in opposite decussate manner (Figs. 57, 58).
5. All the bracts are fertile except a few on the lower side.
6. A single staminate flower or male flower arises in the axil of each bract.
7. Each male flower consists of two bracteoles and a stamen (Fig. 59).
8. Each stamen is a stalked structure with 2 to 4 anthers or microsporangia at the top.
9. Each anther or microsporangium is bilocular or trilocular, and each locule is surrounded by a double-layered wall and an innermost layer of tapetum (Fig. 60).
10. May pollen grains or microspores are present in each locule. Each pollen grain is a uninucleate structure surrounded by a thin intine and thick outer layer of exine.
1. Similar to the male strobilus, the female strobilus also develops in the axil of the leaf on the node.
2. It is sessile and smaller than male strobilus.
3. Two to four pairs of bracts are arranged in opposite decussate manner on the strobilus axis (Figs. 61, 62).
4. Except the uppermost pair of bracts, all are sterile.
5. Two ovules are present in the axil of uppermost pair of bracts (Fig. 62B), out of which generally only one ovule survives.
1. It is covered by a cup-shaped outer integument and an inner integument.
2. Outer integument is attached at the basal part of the ovule (Fig.62D).
3. Inner integument protrudes out of the bracts and outer integument in the form of a long tubular structure.
4. Outer integument is also known as perianth or involucre.
5. A long micropyle is formed by inner integument (Fig. 62D).
6. Integuments enclose the nucellus.
7. Near the micropyle develops a small pollen chamber in the nucellus.
8. Pollen chamber in Ephedra is deepest known among Gymnosperms.
9. Female gametophyte is present in the centre.
10. Archegonia are present in the female gametophyte near the micropylar end.
11. Haustorial region bearing some haustorial processes is present at the end opposite to the micropylar end.
1. Bracts and outer integument surround the entire seed (Fig. 63).
2. Bracts are thick, fleshy and form additional envelope.
3. The outer integument is a very thick structure.
4. The inner integument persists only at the micropylar end.
5. Nucellus is present in the form of a disorganised and shrivelled layer.
6. Embryo remains surrounded by endosperm.
7. Two large cotyledons are present in the embryo.