Angiosperms

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Angiosperms
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Phylum Anthophyta

• Angiosperms
• Seed vessel
• 300,000-450,000 species
• Extremely diverse
• Dominant plant group
• Monophyletic
• Monocots
• Eudicots
• Basal Angiosperms

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GENERALLY!
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wikipedia
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Nutrition

• Most free-living
• Parasites
• Hemi-parasites
• Saprophytes

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Terminology

• Determinate -- growth of limited duration
• Indeterminate unrestricted or unlimited growth
• Inflorescence specific arrangement of flowers

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Flower

• Determinate shoot
• Bears sporophylls
• Fertile
• Androecium
• Gynoecium
• Sterile
• Perianth
• Calyx
• Corolla
• Sepals/Petals vs Tepals
• Receptacle

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Inflorescences
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Placentation

• Parietal
• Axilary fused carpels
• Free Central

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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.htm
  l

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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

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Symmetry

• Regular or Actinomorphic
• Zygomorphic

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Angiosperm Lifecycle
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Angiosperm Life Cycle

• Gametophytes much reduced
• Microgametophyte ? 3 cells
• Megagametophyte ? 7 cells

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Life Cycle

• No antheridia or archegonia
• Pollination indirect ? stigma
• Post-fertilization
• Ovule ? seed
• Ovary ? fruit

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Microsporogenesis Microgametogenesis

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

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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

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Meiosis

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

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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

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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

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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

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Pollen vs Spores

• Trilete spore
• Unaperturate monosulcate pollen

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Megasporogenesis Megagametogenesis

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

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Ovule Structure

• Stalk funiculus bearing nucellus
• Integuments form micropyle

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Ovule Megasporogenesis

• Megasporocyte within nucellus
• Meiosis ? haploid megaspores
• Linear tetrad
• 3 closest to micropyle disintegrate
• Remaining megaspore develops into megagametophyte

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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

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Mature Megagametophyte
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Megagametogenesis

• Most common pattern
• Many (? 11) different patterns
• Sometimes you have cell wall formation

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Pollination Fertilization

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

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Double Fertilization

• One sperm nucleus egg
• Embryo
• One sperm nucleus 2 polar nuclei
• endosperm

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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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