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Chapter 38 - Angiosperm Reproduction

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Chapter 38 - Angiosperm Reproduction

  1. 1. Chapter 38. Plant Reproduction 2005-
  2. 2. Animal vs. Plant life cycle Animal Plant multicellular multicellular sporophyte 2n 2n gametes spores 1n 2n unicellular multicellular gametes gametophyte 1n 1n 2005- alternation of generations
  3. 3. Alternation of generations diploid haploid 2005-
  4. 4. Evolutionary trends  Alternation of generations  dominant haploid plant  bryophytes - mosses  dominant diploid plant  pteridophytes - ferns  gymnosperm - conifers  angiosperm - flowering plants  Evolutionary advantage?  reduction of gametophyte protects delicate egg & embryo in protective sporophyte 2005-
  5. 5. Gametophytes of seed plants Gymnosperm Angiosperm male gametophyte  male gametophyte  pollen in male cone  pollen in anthers of flower female gametophyte  female gametophyte  develops in female  develops in ovaries cone of flower seed  seed  naked in cone  protected in ovary  ovary wall can develop into fruit 2005-
  6. 6. Angiosperm life cycle male gametophyte in pollen female gametophyte in ovary sporophyte in seed 2005-
  7. 7. Flowers 2005-
  8. 8. Flower  Modified shoot with 4 rings of modified leaves  sepals  petals  stamens  male  carpals  female 2005-
  9. 9. Male & female parts of flower 2005-
  10. 10. Male Parts of flower  Stamens = male reproductive organs  stalks (filament) & terminal anthers  pollen sacs produce pollen  pollen grain = gametophyte  sperm-producing structure 2005-
  11. 11. Female Parts of flower  Female carpels = female reproductive organs  Stigma = top of carpel  Sticky  Collects pollen  slender neck = style  ovary at the base  within the ovary are 1 or more ovules  within ovules are embryo sacs  female gametophyte = embryo sac  egg-producing structure 2005-
  12. 12. 2005-
  13. 13. 2005-
  14. 14. Fertilization  Pollination  Pollen grain produces a pollen tube  pollen tube grows down style into ovary & discharges 2 sperm into the embryo sac  1 sperm fertilizes egg = zygote  zygote develops into embryo  ovule develops into a seed  ovary develops into a fruit containing 1 or more seeds  pollen released from anthers is carried by wind or animals to land on stigma 2005-
  15. 15. Preventing self-pollination  Various mechanisms  stamens & carpels may mature at different times  arranged so that animal pollinator won’t transfer pollen from anthers to stigma of same flower  biochemical self-incompatibility = block pollen tube growth 2005-
  16. 16. Fertilization in flowering plants  Double fertilization  2 sperm from pollen  1 sperm fertilizes egg = diploid zygote  1 sperm fuses with 2 polar nuclei to form 3n endosperm  endosperm = food tissue in seed  coconut milk  grains 2005-
  17. 17. Development of the new sporophyte  Cotyledons = bumps on proembryo  “seed leaf” 2005-
  18. 18. Structure & Function of the Seed  Seed coat  Protective layer around the seed  Hypocotyl  Below cotyledons  Embryonic root  Epicotyl  Above cotyledons  Embryonic shoot
  19. 19. From Seed to Seedling Imbition  Uptake of water Enzymes digest endosperm 1st organ = root 2nd organ = shoot 2005-
  20. 20. Fruit  Fruit is a mature ovary  seeds develop from ovules  wall of ovary thickens to form fruit  fruits protect dormant seeds & aid in their dispersal 2005-
  21. 21. Fruit development  peach  1 flower : 1 carpel : 1 ovary : 1 seed 2005-
  22. 22. Fruit development  apple  1 flower : 5 carpels : many ovaries : many seeds 2005-
  23. 23. Fruit development  Citrus fruit  1 flower : many carpels : many ovaries : many seeds 2005-
  24. 24. Fruit development  Raspberry  1 flower : many ovaries : many seeds 2005-
  25. 25. Coevolution of plants & animals  Angiosperms & animals have shaped one another’s evolution  Natural selection reinforced the interactions because they improved the reproductive success of both partners 2005-
  26. 26. Seed dispersal Plants produce enormous numbers of seeds to compensate for low survival rate  a lot of genetic variation for natural selection to screen 2005-
  27. 27. Asexual Reproduction Fragmentation  Separation of parental plants into parts that develop into whole plants Apomixis  Produce seeds without being fertilized  Diploid cell produces embryo 2005-
  28. 28. Asexual Reproduction – Vegetative Reproduction  Callus  Undifferentiated cells that can make new plant from a cutting  Grafting  Combines best qualities of plants  Test-tube plants  Plantlets can be transferred into soil 2005-
  29. 29. Plant Biotechnology Maize  Disease resistance  Cannot spread own  Vitamin content seeds  Golden rice  Artificial selection  Gene containing Bt. toxin beta-carotene (can  Natural pesticide make Vitamin A)  Put into  Prevents blindness cotton, maize, potat oes Herbicide  Reduces need to weed

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