Chapter 38 Plants

Biology, 7th Edition (Book & CD-ROM)

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Chapter 38 Angiosperm Reproduction I. Development of Gametophytes A. Microsporangia 1. Contains many diploids cells (microsporocytes) which are also known as the microspore mother cells 2. Undergoes Meiosis to form four haploid microspores a. Have the potential to make a haploid male gametophyte 3. Microspore undergoes mitosis and cytokinesis (pulling apart of cells) making two separate cells a. Tube cell and generative cell b. Together they make the pollen grain B. Megasporangia 1. One or more ovules form in the ovary a. Ovules have megasporangium in them 2. The megaspore mother cell grows and goes through meiosis forming four haploid megaspores 3. Usually only one megaspore survives and continues to grow a. Nucleus divides by mitosis three times but does not undergo cytokinesis i One large membrane with eight haploid nuclei 4. This mass becomes the embryonic sac (3-2-3 formation) a. Antipodal cells (3) i Function unknown b. Polar nuclei (2) i Share cytoplasm of large central cell c. Ovule (1) i Will eventually become seed ii Consists of embryo sac and two surrounding integuments d. Synergids (2) i Line the egg cell ii Attract and guide pollen tube to embryo sac II. Mechanisms that prevent self-fertilization A. By not self-fertilizing, genetic variety greatly increases 1. Ability to adapt to environmental challenges also increases B. Dioecious Plants 1. Have stamen and carpellate flowers C. Flowers mature at different times 1. It is unlikely that an animal pollinator could transfer pollen from an anther to a stigma of the same flower D. Self-incompatibility 1. A plant rejects its own pollen or the pollen of a plant closely related 2. Biochemical block prevents pollen from completing development III. Ovules and Ovaries Develop A. From Ovule to Seed 1. Each ovule develops into a seed and the ovary into a fruit enclosing the seed(s) 1
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2. Endosperm Development a. Comes before embryo development
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Chapter 38 Plants - Chapter 38 Angiosperm Reproduction I...

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