Plant Reproduction

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• Pollen grain outer wall: develops elaborate structure and secretes chemicals that can interact with those on the stigma to prevent self pollination.
• The female gametophyte is composed of 8 cells that make up the embryo sac.
• Plants can avoid self pollination by:   * Self- incompatibility   * Pollen being developed and dispersed before eggs are matured (temporal separation)   * eggs devolving before pollen is ready (temporal separation)   * Dioecious: Male and female flowers occur on separate plants (spatial separation)   * Monecious: Male and female structures on different flowers (spatial separation)
• The 8 cells of the female gametophyte are composed of: 2 polar nuclei, 1 egg, 2 synergids, and 3 antipodals
• Double fertilization: Occurs only in angiosperms   * One sperm fertilizes the egg producing a diploid zygote   * The other sperm meets with the two polar nuclei to become the triploid endosperm
• Asexual reproduction often occurs in plants living in harsh environments.
• Methods of asexual reproduction:   * Runners/stolons: Above ground stems that produce a new plant. Ex. strawberries   * Rhizomes: Underground stems that produce a new plant. Ex. quack grass   * Suckers: Roots that develop into new plants. Ex. chokecherries   * Adventitious plantlets: Baby plants that develop off of leaves. Ex. Mexican hat
• Germination: The emergence of the radicle through the seed coat. Conditions for germination:   * Moisture   * Oxygen   * Temperature above 5C   * Some require scarification, stratification, or a specific wavelength or intensity of light

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