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Angiosperms

Angiosperms. Phylum Anthophyta. Angiosperms Seed vessel 300,000-450,000+ species Extremely diverse Dominant plant group Monophyletic Monocots Eudicots Basal Angiosperms. GENERALLY!. wikipedia. Nutrition. Most free-living Parasites Hemi-parasites Saprophytes. Terminology.

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Angiosperms

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  1. Angiosperms

  2. Phylum Anthophyta • Angiosperms • Seed vessel • 300,000-450,000+ species • Extremely diverse • Dominant plant group • Monophyletic • Monocots • Eudicots • Basal Angiosperms

  3. GENERALLY!

  4. wikipedia

  5. Nutrition • Most free-living • Parasites • Hemi-parasites • Saprophytes

  6. Terminology Determinate -- growth of limited duration Indeterminate – unrestricted or unlimited growth Inflorescence – specific arrangement of flowers

  7. Flower • Determinate shoot • Bears sporophylls • Fertile • Androecium • Gynoecium • Sterile • Perianth • Calyx • Corolla • Sepals/Petals vsTepals • Receptacle

  8. Inflorescences

  9. Placentation Parietal Axilary – fused carpels Free Central

  10. Terminology • Flower Sex • Perfect – contains all reproductive structures • Pistillate (or Carpellate) – only female structures • Staminate – only male structures • Plant Sex • Monoclinous – all flowers perfect • Diclinous – all flowers imperfect • Monoecious – staminate & pistillate flowers on same plant • Dioecious – staminate & pistillate flowers on different plants • See http://www.ibiblio.org/botnet/glossary/b_v.html

  11. Terminology • Perfect – all reproductive structures • Complete – all 4 floral whorls • Connate – members of one whorl fused • Adnate – members of one whorl fused to another • Ovary position

  12. Symmetry Regular or Actinomorphic Zygomorphic

  13. Angiosperm Lifecycle

  14. Angiosperm Life Cycle • Gametophytes much reduced • Microgametophyte → 3 cells • Megagametophyte → 7 cells

  15. Life Cycle • No antheridia or archegonia • Pollination indirect → stigma • Post-fertilization • Ovule → seed • Ovary → fruit

  16. Microsporogenesis & Microgametogenesis • Separate processes • Microsporogenesis – formation of microspores • Microgametogenesis – development of microgametophyte • Microspores – single-celled pollen grains • Microgametophyte – within pollen grain

  17. Microsporogenesis • Anther structure • 4 groups sporogenous tissue surrounded by sterile tissue • Pollen sac wall including tapetum – nutritive tissue • Sporogenous cells → microsporocytes • Meiosis → tetrad of microspores • Ends with formation of individual microspores

  18. Meiosis • Cell wall formation • Monocots – generally form cell walls after each nuclear division • Eudicots – generally form cell walls simultaneously after 2nd meiotic division

  19. Pollen Grain Structure • Exine – resistant outer wall • Sporopollenin • Derived from tapetum • Composed of carotenoids • Present in spore walls of all plants • Intine – inner wall • Cellulose & pectin

  20. Microgametogenesis • Generally uniform • Mitotic divisions in microspore • Tube cell • Generative cell • 2 celled stage  Immature microgametophyte • Pollen shed – 2/3 sp. • Remainder – generative nucleus divides

  21. Pollen Grains • Taxonomically useful • Most families • Many genera • Some species • Widely represented in fossil record • Palynology • Undergo mitosis within pollen sac • Pollen grains – 2 or 3 nuclei when shed • Spores – 1 nucleus

  22. Pollen vs Spores • Trilete spore • Unaperturate & monosulcate pollen

  23. Megasporogenesis & Megagametogenesis • 2 distinct processes • Megasporogenesis • Formation of megaspore within nucellus (megasporangium) • Inside ovule • Megagametogenesis • Development of megaspore into embryo sac

  24. Ovule Structure Stalk – funiculus – bearing nucellus Integuments form micropyle

  25. Ovule & Megasporogenesis • Megasporocyte within nucellus • Meiosis  haploid megaspores • Linear tetrad • 3 closest to micropyle disintegrate • Remaining megaspore develops into megagametophyte

  26. Megagametogenesis • Megaspore enlarges • 3 mitotic divisions • 2 groups of 4 • One at micropylar end • One group at chalazal end • Polar nuclei • Egg aparatus • Antipodals • Mature megagametophyte

  27. Mature Megagametophyte

  28. Megagametogenesis • Most common pattern • Many ( 11) different patterns • Sometimes you have cell wall formation ……

  29. Pollination & Fertilization • Pollination • Hydration from stigma surface • Germination • Mature microgametophyte • Pollen tube • Grows through stigma • Through micropyle • Penetrates synergid • Fertilization

  30. Double Fertilization • One sperm nucleus – egg • Embryo • One sperm nucleus – 2 polar nuclei • endosperm

  31. Ultimate Fate • Ovule  seed • Ovary  fruit • Ovary wall  pericarp • Integuments  seed coat • Endosperm formation usually before 1st zygotic division • Different types of endosperm formation!

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