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Plant reproductive modes - PowerPoint PPT Presentation

MikeCarlo
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Plant reproductive modes

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  1. Plant reproductive modes • Dominant stage of life cycle: • Moss: gametophyte (sporophyte dependent) • Comparison of reproductive modes of plants: • Fern: Sporophyte (gametophyte independent) • Seed plants: Sporophyte (gametophyte reduced) • Reliance on water for reproduction • Moss: sperm swims in water to egg in archegonium • Fern: sperm swims in water to egg in archegonium • Seed plants: none; pollen transport sperm to egg • Protection of embryo • Moss: ‘embryo’ slightly protected in archegonia • Fern: embryo slightly protected in archegonium • Seed plants: ‘embryo’ well protected in seed coat How are new organisms produced?

  2. Plant reproductive modes • Trends in floral specialization • Primitive flowers have many parts spirally arranged in whorls; radial symmetry (e.g. water lily) • Flowers How are new organisms produced?

  3. Plant reproductive modes • Trends in floral specialization • Separate flower parts become fused (often into a tube) • Flowers • Whorls are ‘lost’ • Flowers show bilateral symmetry How are new organisms produced?

  4. Plant reproductive modes • Terminology • Perfectflower = contains both androecium (male) and gynoecium (female) whorls • Flowers • Imperfectflowers = missing one of ‘sex’ whorls • Staminate flower = male flowers (lack gynoecium whorl) • Pistillate flower = female flowers (lacs androecium whorl) How are new organisms produced?

  5. Plant reproductive modes • Terminology • Imperfect flowers can occur on the same plant (e.g. birch) or on different plants (e.g. aspen) • Flowers • Monoecious = separate staminate and pistillate flowers on the same plant • Dioecious = staminate and pistillate flowers on separate plants How are new organisms produced?

  6. Plant reproductive modes • Pollination • Pollination = process by which pollen is placed on stigma • Flowers • Early seed plants pollinated by wind (like pines) • Earliest flowering plants pollinated by insects; both flowering plants and insects diversified about same time (100 mybp) • Most numerous groups of flowering plants pollinated by bees • Bees locate flowers by odor and flower color • Bee-pollinated flowers tend to be blue or yellow • Many flowers have UV lines or bull’s eyes to indicate the location of nectaries How are new organisms produced?

  7. Plant reproductive modes • Some bees (and wasps) not given nectar or pollen ‘reward’ • Flowers How are new organisms produced?

  8. Plant reproductive modes • Other common pollinators • Butterflies: • Flowers • Flowers have long, slender floral tubes • Flowers have ‘landing platform’ How are new organisms produced?

  9. Plant reproductive modes • Other common pollinators • Moths: • Flowers • Flowers have long, slender floral tubes • Flowers have ‘landing platform’ • White or yellow and heavily scented How are new organisms produced?

  10. Plant reproductive modes • Other common pollinators • Hummingbird: • Flowers • Flowers have long, slender floral tubes • Large amounts of nectar • Red color (conspicuous to birds but not insects) How are new organisms produced?

  11. Plant reproductive modes • Other common pollinators • Bats: • Flowers • Flowers white, heavily scented • Large amounts of nectar How are new organisms produced?

  12. Plant reproductive modes • Wind pollination • Flowers usually small, green, odorless • Flowers • Often grouped together in hanging catkins • Flowers emerge before leaves • Common in grasses How are new organisms produced?

  13. Plant reproductive modes • pollination • Outcrossing = movement of pollen between different flowers • Flowers • Outcrossing prevent inbreeding in plants • Factors that promote outcrossing: • Have separate male and female plants (dioecious plants) • Monoecious plants mature staminate and pistillate flowers at different times • Plants with perfect flowers mature stamen and pistils at different times (= dichogamous) How are new organisms produced?

  14. Plant reproductive modes • Factors that promote outcrossing: • Flowers • Genetic self-incompatibility • Gametophytic: if either allele of stigma matches allele of pollen that pollen’s tube is blocked • Sporophytic: if any allele of pollen matches an allele of stigma no pollen tubes are produced How are new organisms produced?