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Plant reproduction

Plant reproduction. Chapter 38. Fig. 38.3. Plant life cycle. Alteration of generations Haploid (n) Diploid (2n) Sporophyte: Diploid plant produces haploid spores by meiosis Gametophyte: Haploid plant produces diploid zygotes by fertilization. Angiosperms.

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Plant reproduction

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  1. Plant reproduction Chapter 38

  2. Fig. 38.3

  3. Plant life cycle • Alteration of generations • Haploid (n) • Diploid (2n) • Sporophyte: • Diploid plant produces haploid spores by meiosis • Gametophyte: • Haploid plant produces diploid zygotes by fertilization

  4. Angiosperms • Gametophyte generation very small • Enclosed within the parent sporophyte • Pollen grains: • Male gametophytes • Embryo sac: • Female gametophytes • Gametes produced in separate structures

  5. Life cycle

  6. Flower structure • Sepals • Protect the flower • Petals • Attract pollinators • Stamens: male structures • Filaments: “stalks” • Anther: swollen portion at the top

  7. Flower structure • Carpels: female structures • Ovules: develops into seeds • Ovary: contains ovules • Style: slender neck-like structure • Stigma: top collects pollen

  8. Flower structure

  9. Male gametophytes • Pollen formation • Pollen sacs in anther • Microspore: (mother cell) • Meiosis • 4 haploid cells • 4 pollen grains • Inside is a generative cell • Divides later to form 2 sperm

  10. Female gametophytes • Egg formation • Ovules • Contain a megaspore mother cell • Undergoes meiosis 4 haploid cells • 3 die (disintegrate) one lives • Undergoes mitosis 8 haploid nuclei • Arranged in specific order in embryo sac

  11. Female gametophytes • 1 at opening of embryo sac (egg cell) • 2 (single cell) at center polar bodies • 2 contained in cells called synergids on either side of the egg cell • 3 called antipodals at opposite end from egg cell

  12. Fertilization • Pollen sticks to sugary substance on stigma • Grows pollen tube • Reaches ovule • Pollen grain divides into two sperm • One of the synergids degenerates • Tube penetrates the ovule

  13. Fertilization • Double fertilization • 2 sperm are used • 1. Sperm fertilizes egg-zygote (2n) • 2. Sperm fuses with polar bodies • Forms endosperm (3n)

  14. Fertilization

  15. Seed formation • Ovule develops into a seed • Ovary develops into a fruit • Endosperm develops first • Stores food for seed • Most monocots & some eudicots • White coconut meat-endosperm • White part of popcorn-endosperm

  16. Seed structure • Seed coat: • Protective covering • Cotyledons: • Seed leaf • Help with embryo development • Dormancy • Imbibition: • Uptake of water–starts germination

  17. Seed coat Epicotyl Hypocotyl Radicle Cotyledons (a) Common garden bean, a eudicot with thick cotyledons Fig. 38-8 Seed coat Endosperm Cotyledons Epicotyl Hypocotyl Radicle (b) Castor bean, a eudicot with thin cotyledons Pericarp fused with seed coat Scutellum (cotyledon) Endosperm Coleoptile Epicotyl Hypocotyl Coleorhiza Radicle (c) Maize, a monocot

  18. Foliage leaves Cotyledon Epicotyl Hypocotyl Cotyledon Cotyledon Hypocotyl Hypocotyl Fig. 38-9 Radicle Seed coat (a) Common garden bean Foliage leaves Coleoptile Coleoptile Radicle (b) Maize

  19. Fruit formation • Ovary • Simple fruits: • Single carpel-pea, nectarines • Aggregate fruits: • Separate carpels • Raspberry • Multiple fruits: • Group of flowers-pineapples

  20. Stigma Style Carpels Petal Stamen Flower Ovary Stamen Fig. 38-10 Stamen Sepal Stigma Ovary (in receptacle) Ovule Ovule Pea flower Raspberry flower Pineapple inflorescence Apple flower Each segment develops from the carpel of one flower Remains of stamens and styles Carpel (fruitlet) Sepals Stigma Seed Ovary Stamen Seed Receptacle Pea fruit Raspberry fruit Pineapple fruit Apple fruit (a) Simple fruit (b) Aggregate fruit (c) Multiple fruit (d) Accessory fruit

  21. Asexual reproduction • Genetically identical individuals • Vegetative reproduction • Cuttings • Spider plants • Fragmentation • Roots give rise to new plants (Aspens) • Apomixis (seeds produced asexually) • Dandelions

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