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THE FLOWER - PowerPoint PPT Presentation


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THE FLOWER. A flower is a structure specialized for sexual reproduction. A COMPLETE flower has sepals, petals, stamens and carpels. An INCOMPLETE flower is missing one or more of the parts listed for a complete flower. PERFECT vs. IMPERFECT FLOWERS.

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the flower
THE FLOWER
  • A flower is a structure specialized for sexual reproduction.
  • A COMPLETE flower has sepals, petals, stamens and carpels.
  • An INCOMPLETE flower is missing one or more of the parts listed for a complete flower.
perfect vs imperfect flowers
PERFECT vs. IMPERFECT FLOWERS
  • Perfect flowers have both stamens and carpels.
  • Imperfect flowers are either staminate (having stamens but no carpels) or carpellate (having carpels but no stamens).
monoecious vs dioecious plants
MONOECIOUS vs. DIOECIOUS PLANTS
  • Monoecious plants have both staminate flowers and carpellate flowers on the same individual plant.
  • Diocious plants have staminate and carpellate flowers on separate individual plants of the species.
alternation of generations
ALTERNATION OF GENERATIONS
  • An alternation of multicellular haploid (n) and diploid (2n) generations.
  • The sporophyte (2n) produces haploid spores.
  • The spores divide by mitosis to produce haploid gametophytes.
  • The gametophytes produce gametes by mitosis. Fertilization occurs: n+n=2n
pollen grains
POLLEN GRAINS
  • A pollen grain is an immature male gametophyte.
  • Pollen grains are extremely durable; they have tough coats.
formation of pollen
FORMATION OF POLLEN
  • Within the sporangial chamber of the anther, diploid microsporocytes undergo meiosis to form 4 haploid microspores.
  • The haploid microspore nucleus undergoes mitosis to form a generative nucleus and a tube nucleus.
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The wall of the microspore thickens and becomessculptured into a species-specific pattern.
  • The pollen grain has 2 nuclei and is the immature male gametophyte.
  • When the anther opens to release pollen or after pollen lands on the stigma, the generative nucleus divides to form two sperm nuclei, which are the male gametes. The pollen grain is now mature.
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