Sexual

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Chapter 26

• Sexual
• Reproduction
• in Plants

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(I) Structure of the Flower

• Some flowers contain both stamen and pistil while
  other flowers contain only one of the two
• Petals and sepals are also present in flowers

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(I) Structure of the Flower

• The complete circle of petals is called a
  corolla
• The complete circle of sepals is called a calyx.

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(A) Stamen

• Male reproductive structure
• Composed of an anther and filament
• Through meiosis, the diploid cells of the anther
  produce pollen grains that are haploid

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(B) Pistil

• Female reproductive structure
• Composed of stigma, style, and ovary
• As a result of meiosis, the eggs developing
  inside the ovary are haploid

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(III) Pollination

• The transfer of pollen grains from the anther to
  the stigma
• Pollination may be aided by wind, insects, and
  birds. In some instances, the colored petals act
  as a visual attractant for insects
• If pollination occurred in a dry environment, the
  pollen grain would not dehydrate (dry up) due to
  a thick wall that surrounds it
• Two types of pollination
• 1. Self-Pollination
• 2. Cross-Pollination

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Self-Pollination

• The transfer of pollen grains from the anther to
  the stigma of the same plant

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Cross-Pollination

• The transfer of pollen grains from the anther of
  a flower one one plant to the stigma of a flower
  on a different plant
• Allows for variations due to the combination of
  two different plants

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• Following pollination, the pollen grain
  germinates to the stigma and forms a pollen tube
• Pollen tube is an adaptation for internal
  fertilization
• Two haploid sperm cells travel down the pollen
  tube and only one fertilizes the egg in the ovule

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(IV) Fertilization and Embryo Development

• The union of a sperm cell and an egg cell results
  in the formation of a zygote
• The zygote undergoes development resulting in the
  formation of an embryo (ripened ovule)
• The ripened ovule develops into the seed
• The ripened ovary develops into the fruit

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Plant Embryo (seed)

• Hypocotyl- develops into the root, and in some
  species, the lower portion of the stem
• Epicotyl- develops into leaves and the upper
  portion of the stem
• Cotyledon- contains stored food and provides
  nutrients for the germinating plant

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(V) Germination

• In flowering plants, seeds develop within fruits
  which are specialized structures that aid in seed
  dispersal
• Ex animal eats fruit ? feces
• Germination will occur if there is
• 1. Sufficient moisture
• 2. Proper temperatures
• 3. Oxygen

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(VI) Growth

• Growth occurs in specific regions known as the
  meristematic region
• Two types
• 1. Apical meristem- region of growth found in
  the tips of stems and roots (length of plant)
• 2. Cambium- region of growth located between
  the xylem and phloem (width of plant)