Pollen1 - the pistils will fuse for all or part of their...

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Pollen Pollen grains (from the greek palynos for dust or pollen) contain the male gametophyte ( microgametophyte ) phase of the plant. Pollen grains are produced by meiosis of microspore mother cells that are located along the inner edge of the anther sacs (microsporangia). The outer part of the pollen is the exine , which is composed of a complex polysaccharide, sporopollenin. Inside the pollen are two (or, at most, three) cells that comprise the male gametophyte. The tube cell (also referred to as the tube nucleus) develops into the pollen tube . The germ cell divides by mitosis to produce two sperm cells. Division of the germ cell can occur before or after pollination. Gynoecium The gynoecium consists of the stigma , style , and ovary containing one or more ovules . These three structures are often termed a pistil or carpel. In many plants,
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Unformatted text preview: the pistils will fuse for all or part of their length. Like the stamen, the carpel is thought to be a modified leaf. Work by I.W. Bailey and his students pointed to an evolutionary sequence from primitive angiosperms (like Drimys ) to "normal" carpels like those of Lilium .. The Stigma and Style The stigma functions as a receptive surface on which pollen lands and germinates its pollen tube. Corn silk is part stigma, part style. The style serves to move the stigma some distance from the ovary. This distance is species specific. The Ovary The ovary contains one or more ovules, which in turn contain one female gametophyte, also referred to in angiosperms as the embryo sac . Some plants, such as cherry, have only a single ovary which produces two ovules. Only one ovule will develop into a seed....
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This note was uploaded on 11/29/2011 for the course BIO BSC1010 taught by Professor Gwenhauner during the Fall '10 term at Broward College.

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Pollen1 - the pistils will fuse for all or part of their...

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