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SeedPlants213-page8 - strobilus and it is believed that...

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Seed-Dispersing Plants - 8 Reproduction in Cycads Cycads are dioecious. The very large male and female strobili are found on separate plants. The female strobilus may be a meter in length. Sporangia (called pollen sacs in the male) are produced on sporophylls in both female and male. Observe the strobili demonstration materials available. Both male and female sporangia retain the spores after meiosis and male and female gametophytes develop within the diploid sporangia on the sporophyte plants. Male Strobilus Female Strobili Strobilus with Seeds The male gametophyte consists of a pollen grain that contains multiflagellated sperm (as many as 40,000 flagella). Mature pollen is released from the diploid
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Unformatted text preview: strobilus and it is believed that weevils and other beetle species serve as the pollination agents. Once pollen reaches a female gametophyte, retained in the megasporangium of its diploid plant, the male gametophyte grows a pollen tube in through the nucellus of the female gametophyte. Ultimately the base of the microgametophyte ruptures and sperm must swim to the egg. Each male produces two sperm. It may take 4 - 6 months to complete fertilization following pollination. The zygote develops into the seed, still protected by the previous generation diploid sporangial tissue as well as the surrounding female gametophyte tissues. Cycad Sperm...
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