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Coleochaete Life Cycle

Bisexual Gametophytes from the dominant part of this life cycle.
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They produce Oogonia & Antheridia at the tips of Upright Branches.

The Oogonia have Trichogynes.
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Antheridia produce Biflagellate Sperm which lack Plastids.

This represents significant functional specialization because the sperm of Chlorophyta usually resemble a Chlamydomonas vegetative cell. Such cells are autotrophic and can sometimes form asexual propagules. The Sperm of Coleochaete has only one function, fertilization. The Sperm are similar to those of land plants.

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Fertilization produces a Zygote.
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Cells of the Gametophyte overgrow the Zygote to form a
Walled Sporocarp.

This is similar to the formation of a
Calyptra and "Perianth" by the Archegonium & Gametophyte of Liverworts.
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Meiosis occurs inside the Sporocarp.
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Biflagellate Meiospores are released & form Bisexual Gametophytes.

The Gametophytes also produce Mitosporangia which produce biflagellate spores which regenerate gametophytes asexually.

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Reproductive Structures of Coleochaete
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This life Cycle is Oogamous. The Sporophyte is represented by the Zygote which undergoes Meiosis.

In discoid species, Gametangia are produced near the margin of the thallus.

The Antheridia are Multicellular. The Spermatogenous cells are surrounded by a jacket of cells which do not produce sperm. This is similar to the Antheridia of land plants.

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Discoid Coleochaete Thallus viewed with fluorescence. Chlorophyll produces a red fluorescence.

 

 

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Zygotes of a discoid Coleochaete. Gametangia are formed near the margin of the thallus. Thallus tissue grows around the Zygote. The Zygotes form thick, ornamented walls.
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Section of a Young Zygote from a discoid Coleochaete

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