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Vaucheria asexual reproduction examples


There are about 40 species in this genus. Majority of them are fresh water in habit and about half a dozen are marine. Majority of the species of Vaucheria are either aquatic or terrestrial. "Vaucheria asexual reproduction examples" terrestrial species are found upon damp soils and muds in yellowish green velvet-like carpets.

In terrestrial species, the rhizoid-like branches are present at the base of the thallus which attach it to the substratum.

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The fresh water species are usually found in aerated water, e. The thallus consists of branched, coenocytic unseptate and tubular filament.

The septation takes place at the time of the formation of Vaucheria asexual reproduction examples bodies or injury to the plant. The cell wall is thin and consists of "Vaucheria asexual reproduction examples." In the centre of the tubular thallus, there is a big central vacuole. The cytoplasm is confined to the peripheral region.

The numerous discoid chloroplasts are embedded in the cytoplasm towards outside and numerous minute nuclei are found towards the central vacuole. The chloroplasts are devoid of pyrenoids. The strach grains are lacking.

This type of reproduction takes place by accidental breaking of thalli into small fragments. Each fragment of the filament is capable to give rise to a new plant.

The asexual reproduction takes place by several means, e. A single compound zoospore develops in a single zoosporangium. Any distal branch of the thallus may convert into a zoosporangium.

Much of the food reserves, chloroplasts and nuclei accumulate in the distal end of the branch of the thallus. This distal end is comparatively swollen. Very soon a septum appears at the base of this swollen end. The central vacuole disappears, the nuclei and chloroplasts reverse their position, i. The protoplast retracts from the zoosporangial wall and opposite to each nucleus two flagella are developed.

The terminal portion of the zoosporangium softens and a small pore develops. Through this small terminal aperture the zoospore squeezes out and swims freely in the water. The zoospore is ovoid or elliptical.

From each peripheral nucleus, a pair of flagella is given out. There are several chloroplasts arranged inner to the nuclei around the large central vacoule. The nuclei and chloroplasts are embedded in cytoplasm. The zoospore swims for about 15 to 20 minutes and then settles down to some substratum, withdraws its flagella and secretes a wall around it. Very soon it germinates giving rise to 2 or 3 tubular outgrowths and a new branched thallus develops.

The aplanospores develop in Vaucheria asexual reproduction examples conditions and especially in terrestrial forms. Here the contents of an aplanosporangium develop into a non-motile aplanospore. This aplanospore escapes by the irregular rupture Vaucheria asexual reproduction examples the aplanosporangium. On the approach of favourable conditions, the aplanospore germinates producing tubular outgrowths.

They may germinate after liberation or within the aplanosporangium. Sometimes in terrestrial species the segmentation takes place in the tubular branches Vaucheria asexual reproduction examples many small compartments. The hypnospores either germinate directly producing new thalli or they divide producing thin-walled cyst. Each cyst germinates in a special way. The cyst breaks and a pore develops at one end of it.

The protoplast of this comes out in amoeboid fashion, becomes rounded and develops, into a new thallus. The sexual reproduction is oogamous. About all the species reproduce by this method.

All the fresh water species are homothallic. The sexual reproduction takes place in the forms growing in damp soil or still waters. It does not take place in running water species. In the monoecious species the oogonia and antheridia develop on the same Vaucheria asexual reproduction examples and in dioecious species these organs develop on two different thalli.

Here we will consider the sexual reproduction of fresh water forms homothallic. The antheridia develop on the lateral branches at their ends shortly before "Vaucheria asexual reproduction examples" formation of oogonia.

The part of the thallus giving rise to antheridium possesses abundance of cytoplasm, chloroplasts and nuclei. In most of the fresh water species, slender hook-like antheridium develops having a pore at its distal end.

A septum develops just beneath the curved portion of the antheridium. The nuclei of the antheridium divide mitotically again and again, and around each nucleus cytoplasm is deposited. Each such small bit metamorphoses in a biflagellate antherozoid. These antherozoids are liberated through the apical round opening of the antheridium.

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