Which is the gametophyte of fern

The antheridium is the male sex organ. These are small spherical structures that produce flagellate sperm.

Ferns require water to enable the movement of the sperm to reach the egg. A zygote is a combination of genetic material from both the egg and sperm and contains a complete set of DNA to form a new fern plant.

The sperm need to swim through water in order to get to the eggs. The eggs are housed or maintained in the gametophyte, and that dependence on water is why ferns are so often linked to wet habitats. If the sperm do manage to get to an egg, fertilisation occurs, and that is where the two — the sperm and egg — come together. That doubles the number of chromosomes and that gives rise to a whole new typical fern plant again, and the cycle repeats.

The zygote develops from the prothallus fern gametophyte. It grows using mitosis and develops into a young fern plant. The mature fern plant consists of three major parts — the rhizome, the fronds and the sporangia. The mature fern plant is the sporophyte structure that produces spores, which are released from sporangia. Sori are clumps of sporangia that hold the reproductive spores. They are found on the underside of fern fronds. The sporangia is the structure which produces spores.

In ferns, the sporangia are usually aggregated into particular bigger structures. Google Scholar. Progress in wet and dry methodologies, moving from protein catalogs, and the view of classic plant biochemists. Schwartz W Lynn Margulis, Origin of eukaryotic cells. Evidence and research implications for a theory of the origin and evolution of microbial, plant, and animal cells on the precambrian earth.

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The prothallus is haploid, since it grew from a spore which had been formed by meiosis. It does not have any vascular tissue and uses small rhizoids to anchor it to the ground. On the underside of the prothallus the sex organs form. The female structure, called an archegonium, contains a single egg.

The male structure, the antheridium, contains many flagellated sperm. The sperm are released from the antheridium and swim through a thin film of water to a nearby archegonium to fertilize the egg. Since the antheridium and archegonium are on the same prothallus the fern has several strategies to prevent self-fertilization. These strategies will be discussed later in this paper. Once fertilization of the egg has occurred, a diploid zygote has been created.

As the zygote grows into an embryo it remains attached to the prothallus. The embryonic plant depends upon the prothallus for water and nutrients. As the embryo grows and develops into a mature diploid plant the prothallus dies. This mature plant is called the sporophyte generation since it produces spores. The sporophyte plant is the one most commonly recognized as a fern.

The sporophyte then produces new spores as described above. Another method of reproduction ferns use is clonal spreading. Underground rhizomes grow and sprout new sporophyte plants. Huge clonal colonies of ferns have been found that are made up of thousands of individual clonal plants called ramets Klekowski, This extensove clonal spread is especially adaptive for the sporophyte phase. Their long life span several years and extensive competition for space with other plants allows ferns to quickly become the dominant understory plant in newly disturbed areas of the forest.

With archegonia and antheridia on the same gametophyte, one would assume a very high level of inbreeding. Any lethal recessive gene would be expressed and the species would very quickly die out. Intergametophytic selfing, where sperm from one gametophyte fertilized the egg on another gametophyte both having come from the same sporophyte, would also quickly result in homozygosity. In fact, this does not happen. Apogamy induction in Ceratopteris richardii. Plant Sci.

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