38 - 38 Reproduction in Flowering Plants 38 Reproduction in...

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38 Reproduction in Flowering Plants
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38 Reproduction in Flowering Plants How Do Angiosperms Reproduce Sexually? What Determines the Transition from the Vegetative to the Flowering State? How Do Angiosperms Reproduce Asexually?
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38.1 How Do Angiosperms Reproduce Sexually? Sexual reproduction produces new gene combinations and diverse phenotypes. Asexual reproduction produces clones of genetically identical individuals. In agriculture, both are important.
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38.1 How Do Angiosperms Reproduce Sexually? A complete (or perfect) flower has four groups of organs (modified leaves): carpels, stamens, petals, sepals. Carpels are female sex organs. A pistil is composed of one or more carpels. Base of pistil is the ovary , containing ovules , each of which contains a megasporangium . Female gametophyte develops in the megasporangium.
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38.1 How Do Angiosperms Reproduce Sexually? Stamens are the male sex organs. Each has a filament with a two-lobed anther , containing four fused microsporangia . The male gametophyte develops here.
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38.1 How Do Angiosperms Reproduce Sexually? Petals make up the corolla . They are often colored to attract pollinators. Sepals make up the calyx . All the flower parts are attached to the stem tip or receptacle.
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Figure 38.1 Development of Gametophytes and Nuclear Fusion (Part 1)
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Figure 38.1 Development of Gametophytes and Nuclear Fusion (Part 2)
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38.1 How Do Angiosperms Reproduce Sexually? Pollination : transfer of pollen from anther to stigma. NOT THE SAME AS FERTILIZATION! Many mechanisms have evolved for pollen transport. In some plants, such as peas, self pollination occurs before the flower opens, resulting in self-fertilization . When pollen is transferred to a different individual of the same species, it is called cross-pollination .
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38.1 How Do Angiosperms Reproduce Sexually? Some plants reject pollen from their own flowers— self-incompatibility (safe sex ). This promotes genetic diversity. The S gene is responsible for self- incompatibility . It has many alleles. If S allele in pollen matches either S allele in pistil, the pollen grain fails to grow.
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The stigmas of most plants are exposed to pollen of many species. Strong cell–cell signaling between pollen
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This note was uploaded on 04/22/2008 for the course BIOLOGY 020.152 taught by Professor Pearlman during the Spring '08 term at Johns Hopkins.

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38 - 38 Reproduction in Flowering Plants 38 Reproduction in...

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