Seed Formation in Gymnosperms

1
Seed Formation in Gymnosperms Angiosperms
2
Fig. 30-2a
Mosses and othernonvascular plants
Gametophyte
Dominant
Reduced, dependent ongametophyte for nutrition
Sporophyte
Sporophyte(2n)
Gametophyte(n)
Example
3
Fig. 30-2b
Ferns and other seedlessvascular plants
Reduced, independent(photosynthetic
andfree-living)
Gametophyte
Dominant
Sporophyte
Sporophyte(2n)
Example
Gametophyte(n)
4
Fig. 30-2c
Seed plants (gymnosperms and angiosperms)
Reduced (usually microscopic), dependent on
surroundingsporophyte tissue for nutrition
Gametophyte
Dominant
Sporophyte
Gymnosperm
Angiosperm
Microscopic femalegametophytes (n) inside
ovulate cone
Microscopic femalegametophytes (n)
insidethese partsof flowers
Microscopic malegametophytes (n) insidethese
partsof flowers
Example
Microscopic malegametophytes (n) inside
pollencone
Sporophyte (2n)
Sporophyte (2n)
5
Fig. 30-2
PLANT GROUP
Mosses and othernonvascular plants
Ferns and other seedlessvascular plants
Seed plants (gymnosperms and angiosperms)
Reduced, independent(photosynthetic
andfree-living)
Reduced (usually microscopic), dependent on
surroundingsporophyte tissue for nutrition
Gametophyte
Dominant
Reduced, dependent ongametophyte for nutrition
Sporophyte
Dominant
Dominant
Gymnosperm
Angiosperm
Sporophyte(2n)
Microscopic femalegametophytes (n)
insideovulate cone
Microscopic femalegametophytes (n)
insidethese partsof flowers
Sporophyte(2n)
Gametophyte(n)
Example
Microscopic malegametophytes (n) insidethese
partsof flowers
Microscopic malegametophytes (n) inside
pollencone
Sporophyte (2n)
Sporophyte (2n)
Gametophyte(n)
6
Pollen and Production of Sperm

• Microspores develop into pollen grains, which
  contain the male gametophytes
• Pollination is the transfer of pollen to the part
  of a seed plant containing the ovules
• Pollen eliminates the need for a film of water
  and can be dispersed great distances by air or
  animals
• If a pollen grain germinates, it gives rise to a
  pollen tube that discharges two sperm into the
  female gametophyte within the ovule

7
The Evolutionary Advantage of Seeds

• A seed is a sporophyte embryo, along with its
  food supply, packaged in a protective coat
• Seeds provide some evolutionary advantages over
  spores
• They may remain dormant for days to years, until
  conditions are favorable for germination
• They may be transported long distances by wind or
  animals

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Fig. 30-6-1
Key
Haploid (n)
Diploid (2n)
Pollencone
Microsporocytes(2n)
Maturesporophyte(2n)
Pollengrains (n)
MEIOSIS
Microsporangia
Microsporangium (2n)
9
Fig. 30-6-2
Key
Haploid (n)
Ovule
Diploid (2n)
Ovulatecone
Megasporocyte (2n)
Integument
Pollencone
Microsporocytes(2n)
Megasporangium(2n)
Maturesporophyte(2n)
Pollengrain
Pollengrains (n)
MEIOSIS
MEIOSIS
Microsporangia
Microsporangium (2n)
Survivingmegaspore (n)
10
Fig. 30-6-3
Key
Haploid (n)
Ovule
Diploid (2n)
Ovulatecone
Megasporocyte (2n)
Integument
Pollencone
Microsporocytes(2n)
Megasporangium(2n)
Maturesporophyte(2n)
Pollengrain
Pollengrains (n)
MEIOSIS
MEIOSIS
Microsporangia
Microsporangium (2n)
Archegonium
Femalegametophyte
Spermnucleus (n)
Pollentube
FERTILIZATION
Egg nucleus (n)
11
Fig. 30-6-4
Key
Haploid (n)
Ovule
Diploid (2n)
Ovulatecone
Megasporocyte (2n)
Integument
Pollencone
Microsporocytes(2n)
Megasporangium(2n)
Maturesporophyte(2n)
Pollengrain
Pollengrains (n)
MEIOSIS
MEIOSIS
Microsporangia
Microsporangium (2n)
Survivingmegaspore (n)
Seedling
Archegonium
Femalegametophyte
Seeds
Foodreserves(n)
Spermnucleus (n)
Seed coat(2n)
Pollentube
Embryo(2n)
FERTILIZATION
Egg nucleus (n)
12
Fig. 30-3-3
Seed coat(derived fromintegument)
Food supply(femalegametophyte tissue)
Embryo (2n)(new sporophyte)
(c) Gymnosperm seed
13
Angiosperms

• Angiosperms are seed plants with reproductive
  structures called flowers and fruits
• They are the most widespread and diverse of all
  plants

14
Flowers

• The flower is an angiosperm structure specialized
  for sexual reproduction
• Many species are pollinated by insects or
  animals, while some species are wind-pollinated

15

• A flower is a specialized shoot with up to four
  types of modified leaves
• Sepals, which enclose the flower
• Petals, which are brightly colored and attract
  pollinators
• Stamens, which produce pollen on their terminal
  anthers
• Carpels, which produce ovules

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Fig. 30-7
(Female)
(Male)
Stigma
Carpel
(or Pistil)
Stamen
Anther
Style
Filament
Ovary
Petal
Sepal
Ovule
17

• A carpel (or pistil) consists of an ovary at the
  base and a style leading up to a stigma, where
  pollen is received

Video Flower Blooming (time lapse)
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Fruits

• A fruit typically consists of a mature ovary but
  can also include other flower parts
• Fruits protect seeds and aid in their dispersal
• Mature fruits can be either fleshy or dry

Animation Fruit Development
19
Fig. 30-8
Tomato
Ruby grapefruit
Nectarine
Hazelnut
Milkweed
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• Various fruit adaptations help disperse seeds
• Seeds can be carried by wind, water, or animals
  to new locations

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Fig. 30-9
Wings
Seeds within berries
Barbs
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The Angiosperm Life Cycle

• The flower of the sporophyte is composed of both
  male and female structures
• Male gametophytes are contained within pollen
  grains produced by the microsporangia of anthers
• The female gametophyte, or embryo sac, develops
  within an ovule contained within an ovary at the
  base of a stigma
• Most flowers have mechanisms to ensure
  cross-pollination between flowers from different
  plants of the same species

23
The Angiosperm Life Cycle (cont)

• A pollen grain that has landed on a stigma
  germinates and the pollen tube of the male
  gametophyte grows down to the ovary
• The ovule is entered by a pore called the
  micropyle
• Double fertilization occurs when the pollen tube
  discharges two sperm into the female gametophyte
  within an ovule

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The Angiosperm Life Cycle (cont)

• One sperm fertilizes the egg (now a zygote (2n)),
  while the other combines with two nuclei in the
  central cell of the female gametophyte and
  initiates development of food-storing endosperm
  (3n)
• The endosperm nourishes the developing embryo
• Within a seed, the embryo consists of a root and
  two seed leaves called cotyledons

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Fig. 30-10-1
Key
Haploid (n)
Diploid (2n)
Microsporangium
Anther
Microsporocytes (2n)
Mature flower onsporophyte plant(2n)
MEIOSIS
Generative cell
Microspore(n)
Tube cell
Male gametophyte(in pollen grain)(n)
Pollengrains
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m-microgpyt.html
Each microspore divides by mitosis to form two
haploid nuclei (the tube nucleus and the
generative nucleus)
A diploid microsporocyte, or microspore mother
cell, divides to give rise to four haploid
microspores.
After landing on the stigma, the pollen
germinates forming a pollen tube the generative
nucleus then divides by mitosis to form two
haploid sperm nuclei.
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Fig. 30-10-2
Key
Haploid (n)
Diploid (2n)
Microsporangium
Anther
Microsporocytes (2n)
Mature flower onsporophyte plant(2n)
MEIOSIS
Generative cell
Microspore(n)
Ovule (2n)
Tube cell
Male gametophyte(in pollen grain)(n)
Ovary
Pollengrains
MEIOSIS
Megasporangium(2n)
Megaspore(n)
Antipodal cellsCentral cell (or polar bodies
that form endosperm)SynergidsEgg (n)
Female gametophyte(embryo sac)
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m-microgpyt.html
The remaining megaspore nucleus undergoes three
mitotic divisions to form eight haploid nuclei.
A diploid megasporocyte (megaspore mother cell)
undergoes meiosis, giving rise to four haploid
megaspore nuclei (3 of which disintegrate).
Nuclear migration and cytokinesis occur to form
the mature megagametophyte
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Fig. 30-10-3
Key
Haploid (n)
Diploid (2n)
Microsporangium
Anther
Microsporocytes (2n)
Mature flower onsporophyte plant(2n)
MEIOSIS
Generative cell
Microspore(n)
Ovule (2n)
Tube cell
Male gametophyte(in pollen grain)(n)
Ovary
Pollengrains
MEIOSIS
Stigma
Megasporangium(2n)
Pollentube
Sperm
Megaspore(n)
Style
Antipodal cellsCentral cellSynergidsEgg (n)
Female gametophyte(embryo sac)
Pollentube
Sperm(n)
FERTILIZATION
Eggnucleus (n)
Discharged sperm nuclei (n)
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Fig. 30-10-4
Key
Haploid (n)
Diploid (2n)
Microsporangium
Anther
Microsporocytes (2n)
Mature flower onsporophyte plant(2n)
MEIOSIS
Generative cell
Microspore(n)
Ovule (2n)
Tube cell
Male gametophyte(in pollen grain)(n)
Ovary
Pollengrains
MEIOSIS
Germinatingseed
Stigma
Megasporangium(2n)
Pollentube
Embryo (2n)Endosperm (3n)Seed coat (2n)
Sperm
Seed
Megaspore(n)
Style
Antipodal cellsCentral cellSynergidsEgg (n)
Female gametophyte(embryo sac)
Pollentube
Sperm(n)
Nucleus ofdevelopingendosperm(3n)
FERTILIZATION
Zygote (2n)
Eggnucleus (n)
Discharged sperm nuclei (n)
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Practice!!!

• http//bio.rutgers.edu/gb101/lab8_angio_repro/ind
  ex.html