1. Plant Reproduction Chapter 42
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2. Rise of the Flowering Plants
Virtually all our food is derived, directly or indirectly, from flowering plants.
Also sources of medicine, clothing, and building materials.
Much of early angiosperm evolution may have taken place in patches of drier or unfavorable habitat in the interior of Gondwanaland.
Outcrossing may have been important in early success.
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3. Evolution of the Flower
Pollen matures within the anthers and is transported to the stigma of another flower.
When pollen reaches the stigma, it germinates, and a pollen tube grows down, carrying sperm nuclei to the embryo sac.
Seed matures within ripening fruit.
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4. Evolution of the Flower
Characteristics
A complete flower has four whorls, while an incomplete flower lacks at least one.
Calyx, composed of sepals, makes up outermost whorl.
Petals collectively make up the corolla.
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5. Evolution of the Flower
Characteristics
Male part:
Stamens collectively compose androecium.
Stamens made up of filament and anther.
Female part:
Gynoecium refers to the collection of female parts in a flower.
Single or fused carpels also referred to as simple or compound pistils.
Ovules produced in pistil’s swollen ovary.
Style - Slender neck.
Stigma - Pollen-receptive structure.
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6. Evolution of the Flower
Trends in Floral Specialization
Separate floral parts have fused.
Floral Parts have been lost or reduced.
Resultant of natural selection and artificial breeding.
Trends in Floral Symmetry
Many flowers of advanced groups are bilaterally symmetrical.
Often associated with advanced pollination systems.
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7. Formation of Angiosperm Gametes
Plant sexual life cycles are characterized by an alternation of generations.
Diploid sporophyte gives rise to haploid gametophyte generation.
Male gametophytes (microgametophytes) - Pollen grains
Female gametophyte (megagametophyte) - Embryo sac
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8. Formation of Angiosperm Gametes
Angiosperms have separate structures for reproduction . Similar to animals, except:
Male and female structures usually occur together in the same individual flower.
Angiosperm reproductive structures are not permanent parts of the adult individual.
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9. Formation of Angiosperm Gametes
Pollen Formation
Each pollen sac contains specialized chambers enclosing microspore mother cells.
Undergo meiosis to form four haploid microspores.
Pollen grain shapes are specialized for specific flower species.
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10. Formation of Angiosperm Gametes
Embryo Sac
Megaspore mother cell found within each ovule.
Undergoes meiosis to produce four haploid megaspores.
Usually only one survives and the other three are absorbed by the ovule.
Remaining megaspore undergoes mitosis and produces eight haploid nuclei enclosed in an embryo sac.
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11. Pollination - Pollen is placed on the stigma.
Early seed plants pollinated passively.
Pollination by Animals
Bees - Initially locate food sources by odor, and then orient on a flower by its shape, color, and texture.
May drive coevolution.
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12. Pollination Other Insects Butterflies Moths Beetles Birds
Many plants produce large amount of nectar to attract birds.
Hummingbirds
Red colors tend to attract birds, while carotenoids tend to attract insects because they are visible in the UV range.
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13. Wind-Pollinated Angiosperms
Pollination
Other Animals
Bats
Rodents
Monkeys
Wind-Pollinated Angiosperms
Typically have small, greenish, odorless flowers with reduced or absent corollas.
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14. Two basic reasons for self-pollination.
Ecologically advantageous as they do not need to be visited by animals, and thus do not have to expend energy producing attractants.
Produces more uniform progeny than outcrossing.
Well-adapted to particular habitats.
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15. Factors Promoting Outcrossing
Self-Pollination
Factors Promoting Outcrossing
Dioecious plants produce only ovules or only pollen on a single individual.
Monoecious produce both on same plant.
Dichogamous - Functional stamens and pistils present on same plant, but reach maturity at different times.
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16. Self-Pollination
Self-incompatibility results when pollen and stigma recognize each other as genetically related and pollen tube growth is blocked.
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17. Fertilization Double Fertilization results in two key developments:
Fertilization of the egg.
Formation of endosperm.
Pollen grains adhere to the stigma and grow a pollen tube that pierces the style.
Grows until it reaches the ovule in the ovary.
Tip of pollen tube bursts and releases two sperm cells.
One fertilizes the egg cell forming a zygote.
The other cell fuses with two polar nuclei located at the center of the embryo sac.
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18. Vegetative Reproduction - New plants are cloned from adult parts.
Asexual Reproduction
Vegetative Reproduction - New plants are cloned from adult parts.
Runners
Rhizomes
Suckers
Adventitious Plantlets
Apomixis - Embryos in seeds produced asexually from the parent plant.
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19. Once established, plants live for highly variable periods of time.
Life Span of Plants
Once established, plants live for highly variable periods of time.
Life span may or may not correlate with reproductive strategy.
Woody plants which have extensive secondary growth, nearly always live longer than herbaceous plants, which have limited to no secondary growth.
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20. Grow rapidly under favorable conditions.
Life Span of Plants
Annuals
Annual plants grow, flower, and form fruits and seeds within one growing season, and then die when the process is complete.
Grow rapidly under favorable conditions.
Developing flowers or embryos use hormones signaling nutrient reallocation.
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21. Biennial plants have life cycles that take two years to complete.
Life Span of Plants
Biennials
Biennial plants have life cycles that take two years to complete.
Photosynthate stored in underground storage organs during the first year.
Flowering stems are produced during the second year.
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22. Perennial plants grow year after year.
Life Span of Plants
Perennials
Perennial plants grow year after year.
Majority of vascular plants are perennial.
Food is often stored in roots or underground stems which can become relatively large.
Trees and shrubs generally flower repeatedly.
Deciduous or Evergreen.
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23. Life Span of Plants Organ Abscission
Abscission - Shedding of leaves or petals.
Dispense with nutrient sinks.
Shaded leaves, petals
Evergreens usually have complete change of leaves every two to seven years.
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24. Life Span of Plants
Abscission involves changes in abscission zone at the base of the petiole.
Young leaves produce hormones that inhibit development of specialized layers of cells in the abscission zone.
Cells become impregnated with suberin.
Separation layer develops on the side of the leaf blade; cells of the separation layer divide, swell, and become gelatinous.
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25. Copyright © McGraw-Hill Companies Permission required for reproduction or display
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