Lab_6-_gymnosperms_ - Lab #6 – Gymnosperms By Ioana Dobre...

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Unformatted text preview: Lab #6 – Gymnosperms By Ioana Dobre • Like ferns, gymnosperms have a well developed alternation of generations • Gametophytes are microscopic + completely dependent on the large free-living sporophyte • 4 phyla: Cycadophyta , the Ginkophyta , Coniferophyta , and Gnetophyta Coniferophyta – Pinus Coniferophyta – Pinus • “microsporangiate cones” = male cones • Microsporophylls are arranged helically along axis of the cone • Each microsporophyll bears 2 microsporangia or pollen sacs in which the microspore mother cells are formed • each microspore mother cell undergoes meiosis and gives rise to 4 microspores • These develop into the pollen grains , or immature male gametophytes - At the time the pollen grains are shed, they consist of 4 cells: *2 prothallial cells *a generative cell *a tube cell Microsporangiate (pollen-producing) cones Microsporangiate cones are small and the microsporophylls are spirally arranged along the axis-each microsporophyll hosts 2 microsporangia (pollen sacs) microspores microsporangium microsporophyll Pollen-producing cone microsporangia Bladder-like wings Prothallial cells (should be 2) Generative cell *excellent microscope photos in the textbook Pollen grain section (4 types of cells) Tube cell •...
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This note was uploaded on 02/21/2012 for the course BIO Bio2137 taught by Professor Namroud during the Fall '11 term at University of Ottawa.

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Lab_6-_gymnosperms_ - Lab #6 – Gymnosperms By Ioana Dobre...

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