Chapter 38 - CR97-03

Chapter 38 - CR97-03 - Chapter 38 Angiosperm Reproduction...

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Chapter 38 Chapter 38 Angiosperm Reproduction and Biotechnology 1 of 17
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38.1: Pollination enables gametes to 38.1: Pollination enables gametes to come together come together within a flower within a flower In angiosperms, the dominant sporophyte Produces female gametophytes (embryo sacs) Produces spores that develop within flowers into male gametophytes (pollen grains) Flowers are the reproductive shoots of the angiosperm sporophyte Are composed of four floral organs: sepals, petals, stamens, and carpels Many variations in floral structure have evolved during the 140 million years of angiosperm history 2 of 17
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Bilateral symmetry (orchid) Sepal Radial symmetry (daffodil) Fused petals Semi-inferior ovary Inferior ovary Superior ovary Lupine inflorescence Sunflower inflorescence SYMMETRY OVARY LOCATION FLORAL DISTRIBUTION Figure 38.3 3 of 17
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In angiosperms… Pollination is the transfer of pollen from an anther to a stigma If pollination is successful, a pollen grain produces a structure called a pollen tube , which grows down into the ovary and discharges sperm near the embryo sac Pollen d evelops from microspores within the sporangia of anthers Embryo sacs develop from megaspores within ovules Many angiosperms have mechanisms that make it difficult or impossible for a flower to fertilize itself… 4 of 17
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Mechanisms That Prevent Self- Mechanisms That Prevent Self- Fertilization Fertilization The most common anti-selfing mechanism in flowering plants is known as self- incompatibility , the ability of a plant to reject its own pollen Some plants reject pollen that has an S -gene matching an allele in the stigma cells Recognition of self pollen triggers a signal transduction pathway leading to a block in growth of a pollen tube Stigma Anther with pollen Stigma Pin flower Thrum flower Figure 38.5 5 of 17
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38.2: After fertilization, ovules develop 38.2: After fertilization, ovules develop into seeds and ovaries into fruits into seeds and ovaries into fruits Double Fertilization A pollen grain germinates and produces a pollen tube that extends down between the cells of the style toward the ovary The pollen tube then discharges
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This note was uploaded on 04/07/2008 for the course BIO 103 taught by Professor Mannino during the Fall '08 term at Long Island U..

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Chapter 38 - CR97-03 - Chapter 38 Angiosperm Reproduction...

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