Effect of Population Density in Sexual Development,

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The gametophytes used in this experiment are of C-ferns. They tend to mature and produce spores at temperature of 28oC and conditions of high humidity. The spores that germinate first are hermaphrodites. Hermaphrodites tend to produce a pheromone called antheridiogen. It is this pheromone that causes later germinating spores to become male.

In wild type culture of C-ferns, it is expected that there will be a high concentration of antheridiogen since the hermaphrodites are producing antheridiogen. The greater the population density of C-ferns, the higher the concentration of antheridiogen; hence a high percentage of male gametophytes in the wild type cultures.

In the experiment, a culture of her1 culture was used to investigate the effect of population density on sexual development of the C-fern Gametophytes. What was unusual about the her1 culture is that no males were present in the culture.

It is either that no antheridiogen was produced by the her1 hermaphrodites hence the absence of male gametophytes or the her1 gametophytes do not have receptors to perceive the antheridiogen which could result in the absence of the male gametophytes.

If the hypothesis that the her1 hermaphrodites do not produce antheridiogen is correct, the wild type culture and her1 filtrate will have the same percentage of males as the wild type culture and distilled water. If the hypothesis that her1 do not have receptors that perceive antheridiogen is correct, then her1 culture and wild type filtrate will have the same percentage of males as her1 culture and distilled water.

Results

As the population density increased, so did the male gametophytes of the wild type strain; but there were no male gametophytes at any population density in the Her ...

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...ermine which gametophytes were less responsive to antheridiogen from the number of males that were produced after we set-up the experiments. Just the same way as the authors, we had to determine the cause of the insensitivity in response of the insensitive gametophytes by carrying out different experiments with different conditions to determine whether the gametophytes did not produce antheridiogen or maybe they did not perceive the antheridiogen. In the same way we found out that her1 culture could not perceive antheridiogen just the same way as the authors found out that the insensitive mutant could not perceive antheridiogen.

References

• Thomas R. Warne, Leslie G. Hickok and Rodney J. Scott. (1988). Botanical Journal of the Linnean Society. Characterization and genetic analysis of antheridiogen-insensitive mutants in the fern Ceratopteris. 96 (1), 371-379.

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