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Flowers and Reproduction

Flowers and Reproduction. Dr. Gough. Figure 09.07A: (a) The sepals of this rose form a tight covering over the rest of the flower as it develops, protecting the inner parts. Flower Structure. Ovary Position Protect ovary from pollinators. Fig. 9-28. Flower Structure.

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Flowers and Reproduction

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  1. Flowers and Reproduction Dr. Gough

  2. Figure 09.07A: (a) The sepals of this rose form a tight covering over the rest of the flower as it develops, protecting the inner parts.

  3. Flower Structure • Ovary Position • Protect ovary from pollinators Fig. 9-28

  4. Flower Structure • Stem with leaf-like structures • Terminology • Pedicel and receptacle • Complete vs. incomplete flowers • Sepals (calyx) • Petals (corolla) • Stamens (androecium) • Carpels (gynoecium)

  5. Reproduction • Two forms of reproduction • Produce identical genetic copies • Produce genetically different offspring • What conditions favor which form? • How does sexual reproduction produce genetically different offspring? • Some plants reproduce both ways

  6. Asexual Reproduction • Many methods • Fragmentation • Rhizomes • Stolons

  7. Figure 09.02C: (c) All the trees in this photograph are a part of the same plant, each a sprout from a single root system.

  8. Sexual Reproduction • In angiosperms, requires flowers • Plant Life Cycle • Think of human/animal life cycle • Meiosis • Fertilization • Mitosis • More complicated in plants • “alternation of generations”

  9. Figure 09.13: This is the tip of a growing pollen tube. It was treated to make the nuclei fluoresce so that they can be found despite being so small. Courtesy of S. Muccifora

  10. Sexual Reproduction • Fertilization • Following pollination • Pollen tube growths through style to ovule opening • One sperm nucleus fertilizes egg • Second sperm nucleus migrates into central cell • Only in angiosperms • Becomes endosperm • “Double fertilization”

  11. Sexual Reproduction • Embryo and Seed Development • Zygote continues dividing, growing • Embryo • Radicle • Hypocotyl • Epicotyl • Monocotyledon • Dicotyledon

  12. Figure 09.19A: (a) This bean seed has begun germinating; the radicle has extended and will develop into a taproot.

  13. Figure 09.19C: (c) The small leaves present on the epicotyl are expanding during germination.

  14. Sexual Reproduction • Fruit Development • Fruit is a mature ovary

  15. Figure 09.21: In apples, the petals die and fall off after pollination.

  16. Figure 09.22B: (b) Coconuts in stores are usually just the endocarp and seed.

  17. Flower Structure and Cross-Pollination • Role of flowers in pollen and seed dispersal • Cross-pollination • Vs. self-pollination • Stamen and style maturation times • Stigma and pollen incompatibility

  18. Flower Structure and Cross-Pollination • Monoecious and dioecious species • Imperfect vs. perfect flowers • Monoecy • Dioecy Fig. 9-25

  19. Flower Structure and Cross-Pollination • Animal-pollinated flowers • Coevolution between plants and pollinators • Plant-insect pollination began about 120 mya • What traits were favored? • Some birds and bats pollinate too • Flower shape • Actinomorphic/regular vs. zygomorphic • Usually positive relationship, but cheaters on both sides

  20. Fruit Types and Seed Dispersal • More co-evolution! • Seed (fruit) dispersal agents • Gravity • Wind • Water • Animals • Often division of labor within fruit

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