Angiosperms

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Angiosperms

• Earths dominant plants

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Angiosperm Characteristics

• Vascular
• Flowering plants
• Double fertilization
• Seeds are covered in a fruit

• Dominant sporophyte generation
• Xylem vessel elements
• Phloem sieve tube elements

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2 Largest Classes

• Eudicots
• Roses, sunflowers, maples
• Herbaceous or woody
• Branched veins
• Flowers multiples of 4 or 5
• Seed 2 cotyledons

• Monocots
• Grasses, corn, palms
• Mainly herbaceous
• Parallel veins in leaves
• Flower parts multiples of 3
• Seed 1 cotyledon, endosperm

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Flowers

• Reproductive part of angiosperms
• 4 parts sepals, petals, stamens, carpels
• Complete vs. Incomplete flowers
• Perfect vs. Imperfect flowers

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Reproduction

• Pollination
• Wind
• Water
• Pollinators
• Double Fertilization
• Germination

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What happens in the anther?

• Pollen sac contains many microsporocytes
• Meiosis ? 4 haploid microspores
• Each microspore ? pollen grain (immature male
  gametophyte
• Each pollen grain contains 2 cells
• Tube cell
• Generative cell
• Anther splits sheds pollen

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What happens in the pistil?

• Each ovule in ovary contains megasporocyte
• Meiosis ? 4 haploid megaspores
• 3 megaspores disintegrate
• Remaining megaspore divides ? gametophyte (aka
  embryo sac)
• Gametophyte contains 7 cells w/ 8 nuclei
• Egg cell contains 1 nucleus
• Large center cell contains 2 polar nuclei

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Double Fertilization

• Pollen lands on sticky stigma
• Tube cell forms pollen tube through style into
  ovary
• Generative cell divides ? 2 sperm cells
• Double Fertilization
• 1 sperm fertilizes egg ? zygote ? embryo
• 1 sperm fuses with both polar nuclei ? 3n cell ?
  endosperm

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Seed and Fruit Formation

• Ovule develops into seed
• Ovary wall enlarges
• Ripens into fruit
• Flower parts fall off
• Fruits
• Protect seeds from dessication
• Aid in dispersal

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Success of Flowering Plants

• Seeds an advantage over spores
• Cross-pollination increases variation
• Animals disperse pollen and fruit farther than
  wind

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• Efficient xylem
• Vessel elements
• Broad leaves
• efficient photosynthesis
• Abscission
• Reduces water loss
• Adaptability of sporophyte generation