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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Beneath this region the cortex again consists of compact parenchymatous tissue acting as storage tissue containing starch in them. Xylem is situated in the centre which is diarch and exarch. The remaining portion of the spore is filled with a frothy cytoplasm full of starch grains Fig.
In submerged species, however, the mesophyll is not differentiated into palisade and spongy parenchyma. All species possess the siphonosteles externally and internally limited by a single layered endodermis.
The sporocarp may easily be germinated by injuring it on the ventral median line and keeping it in the water. Young leaves show circinate vernation like ferns Fig. Answer Now and help others. Mrsilea the pinnas are once or twice deeply dichotomously lobed M. It is also called aerenchyma. Top 17 Problems on Statistics With Solution.
Each microspore is a unicellular, uninucleate, thick walled globose and haploid structure, ranging from 0- to 0- mm in diameter. Just beneath the upper epidermis there is mesophyll differentiated into palisade and spongy tissues. How does it affect the heart?
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Each sorus arises on a ridge like placenta or receptacle formed on the sporocarp wall. This way, the continuation of different tissue in the amphiphloic siphonostele is as follows-outer endodermis, outer pericycle, outer phloem, xylem, inner phloem inner pericycle and then inner endodermis. The first division of the zygote is vertical in relation to the neck of the archegonium followed by a transverse division resulting in the quadrant stage four-celled stage of the marsilfa Fig.
The venation is of closed reticulate type. In the centre is present a cavity filled with microspore mother cells Fig.
The vascular bundles are concentric, i. There are two main hypotheses:. Its underground rhizome spreads in a diameter of 25 meter or more.
Useful Notes on the Life History of Marsilea ( Words)
In majority of cases the peduncle or stalk of the sporocarp is unbranched and bears a single sporocarp at its apex. They arise solitary or in clusters. In certain cases the roots are given out even from the internodes M. This hypothesis has been discussed in detail in the following lines:. Slightly above the raphe in a median plane are present 1 or 2 protuberances called tubercles.
Bugen interpreted that the sporocarp has been resulted from the opposition of two leaflets pinnaewhereas Bower and Campbell interpreted that the sporocarp has been resulted from a single pinna by its enfolding. The stem is long, slender and freely-branched rhizome of indefinite growth that grows on or just below the soil surface.
It has been observed in Marsilea vestita that as soon as the spore begins its germination, the nucleus becomes spherical and at the anterior end, the granular cytoplasm increases in amount. Each sorus appears to be formed in a cavity and is surrounded by a delicate, membranous indusium. The zygote divides first by a vertical division. The sporocarp initial forms a mass of undifferentiated cells by cutting segments on both lateral sides.
It is the outermost surrounding layer and is only one cell in thickness. The primary tapetal cells divide periclinally as well as anticlinally to form a two layered tapetum. The aquatic species — M. Leave a Reply Click here to cancel reply.
The following tissues are seen in the transverse section. The outer exine is covered by a thin layer called perispore. In mature sporocarp the cells of this zone gelatinise and form a gelatinous ring which helps in the dehiscence of the sporocarp. Thus, a four-celled embryo is formed.
It bears the special structures known as sporocarps which contain micro and megasporangia in them. The inner cortex is differentiated into outer parenchymatous and inner sclerenchymatous regions. When the plants grow on mud or marshy places the leaves have got shorter and the petioles erect and stouter which spread the leaves in the air. Each sporocarp possesses many sori which bear microsporangia and megasporangia.
This transverse wall develops in between the denser cytoplasm of the protuberance and the remaining watery cytoplasm.
The species of Marsilea possess a rhizome which creeps on or just beneath the surface of the soil.