LIFE CYCLE OF MARSILEA PDF

Here are your notes on the life history of Marsilea! Characteristic features: This order includes a single family, Marsileaceae. The family includes the living. Etiology Thiaminases occur naturally in Marsilea spp., Cheilanthes spp., Figure A. Growth habit and reproductive structures of the sporophyte polypody fern. .. that centriolar duplication connected to the cell cycle is a secondary event. Download/Embed scientific diagram | – Life cycle of a Heterosporous Pteridophyte (eg: Marsilea) from publication: Diversity of Pteridophytes in Western Ghats.

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The vascular supply of the sporocarp consists of a main vein along the narrow side facing the peduncle from which numerous lateral veins perpendicular to the main vein dorsal bundle are given off. The epidermis is interrupted by a number of stomata.

The shape of pinna varies from obovate to obcuneate and margin also varies from entire to crenate or crenate to lobed. In megasporangium, only one megaspore survives to become a large functional megaspore, while all the microspores are functional in microsporangium. The cortex of the root is differentiated into two regions. Each megaspore is a unicellular, uninucleate, ellipsoidal structure with an apical papilla Fig.

The development of megasporangium is exactly in the same way as that of microsporangium except that out of the total number of megaspores formed, all degenerate leaving except one which behaves as a functional megaspore x. The sporangia of these are produced within special structures known as sporocarps. The stele is protostelic with diarch and exarch xylem. The sorus contains micro and megasporangia.

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The inner cortex is composed of compact parenchymatous cells. It divides transversely into an outer and inner cell Fig. Under some unfavourable circumstances the subterranean branches of the rhizome form tubers. Just beneath the epidermis there is hypodermal layer.

The following tissues are seen in the transverse section. In some species e. It possesses a large central nucleus and a large number of small starch grains scattered throughout the cytoplasm. At the time of their separation from the gelatinous ring the ventral ends of the sori are torn off and sporangia of with spores escape from the ventral ends of the sori megaspore mother cells However, the indusia and the jackets of sporangia become gelatinized and the spores are liberated.

The inner cortex is differentiated into outer parenchymatous and inner sclerenchymatous regions. The internal structure of the sporocarp in transverse, longitudinal and dorsiventral sections is as follows:.

It is chcle just below the epidermis, also called hypodermis. It possesses V-shaped mass of xylem with the exarch protoxylem. After the microspores and megaspores are shed from the sporangia, separate male and female gametophytes develop. The structure of the outer wall of the mrasilea and gelatinous ring is the same as seen in transverse and longitudinal sections.

One of the superficial cells acts as a sporangial initial. The vascular bundles are concentric, i.

Marsilea: Habitat, External Features and Reproduction

It is made of thin walled cells parenchymatous. In majority of the species of Ov near the point of attachment of the stalk or peduncle at the base, marsiea are usually one and sometimes more protuberances in the median plane. The spore wall is quite thick. In this region some of the tannin cells may be present here and there. The sporangium wall of Marsilea shows no sign of cellular specialisation e. In some cases the tubercles are absent e.

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Phloem bands are present on either side of Fig. Each sorus is surrounded by an indusium. The inner cell further divides by periclinal division to form a second smaller jacket cell and a large outer cell Fig. The apical cell, immediately after its formation divides diagonally to the prothallial cell producing two antheridial initials. It increases in size.

At the tip of the sorophore there marsilwa certain small gelatinous projections, also alternate with one another.

Marsilea: Habitat, External Features and Reproduction

There are two main hypotheses:. It is green and soft when it is young but at maturity it becomes very hard and brown in colour. At this stage the male gametophyte consists of one prothallial cell, 6 jacket cells and 2 androgonial cells.