Flowering Plants
Domain Eukarya
Kingdom Plantae
Phylum Anthophyta/Magnoliophyta
SYNGAMY
zygote
SporophyteGametophyte
sporangium
sporocytespores
gametangia
gametesgermination
mitosis
differentiation
mitosisgerminationmitosis
mitosis
1N 2N
differentiation
differentiation
differentiation
MEIOSIS
Life Cycle of Flowering Plants
The flowering plant is a multicellular diploid sporophyte.
The sporophyte encloses the multicellular haploid gametophyte.
The life history is thus sporic (diplohaplontic).
The gametes are oogamous but the sperm lack flagellae.
Gender expression has moved from gametophyte to sporophyte.
androecium
petal corolla
calyx
gynoecium
¢
™stigma
style
ovary
ovule
locule
filament
anther
sepal
pedicel
receptacle
carpel
stamen
completeperianth
flowerperfect
superior
flower hypogynous
pollen
Flower Organization-building a flower from bottom up
A flower is a short shoot (stem with leaves)The stem is represented by the receptacle with very short internodesThe leaves appear in four whorls
http://images.iasprr.org/lily/lpachy-m.jpg
Microsporogenesis: Prophase I of Meiosis
http://images.iasprr.org/lily/lepto.jpg
Microsporogenesis: Late Prophase I of Meiosis
http://images.iasprr.org/lily/meta-i.jpg
Microsporogenesis: Metaphase I of Meiosis
http://images.iasprr.org/lily/anaph.jpg
Microsporogenesis: Anaphase I of Meiosis
http://images.iasprr.org/lily/telo-i.jpg
Microsporogenesis: Telophase I of Meiosis
http://images.iasprr.org/lily/meta-ii.jpg
Microsporogenesis: Metaphase II and Anaphase II of Meiosis
http://images.iasprr.org/lily/telo-ii.jpg
Microsporogenesis: Telophase II of Meiosis
http://images.iasprr.org/lily/tetrad.jpg
Microsporogenesis: Meiosis complete (but prophase of mitosis)
http://images.iasprr.org/lily/microsp.jpg
Microsporogenesis: Completed, Separated Microspores (note prophase)
http://images.iasprr.org/lily/pollen2.jpg
Pollen Grain: Mitosis Makes Endosporic Microgametophyte
Tube Cell
Nucleus
Cytoplasm
Generative Cell
Nucleus
Cytoplasm
The tube cell digests a path from the stigma to the egg.
The generative cell follows the path to the egg, and divides to make two sperm cells. Both participate in syngamy.
Pollination: vector-assisted movement of the
pollen grain from the anther to the stigma.
Pollen Wall: Microspore Wall (allergenic?)
http://bilbo.bio.purdue.edu/~cjslab/pollen-tubes.jpg
Pollen Tube GrowthThe tube cell germinates through the pollen wall.The cell grows chemotropically toward the egg.The pollen tube must find the ovule’s micropyle.The generative cell slides along this tube.It divides by mitosis to form two sperm cells.
Megasporogenesis: taking place inside the ovule inside the ovary.
megasporocytemeiosis I meiosis II
4 megaspores3 disintegrate
functionalmegaspore
mitotic divisions without cytokinesis
cytokinesis
megagametophyte
egg
central cell
3 antipodals
2 synergids
http://botit.botany.wisc.edu/courses/img/Botany_130/Diversity/Angiosperms/Fertilization.jpg
1N egg + 1N sperm = 2N zygote
syngamy#1:
syngamy#2:
2 x 1N polar nuclei + 1N sperm = 3N primary endosperm cell
In Flowering Plants, syngamy is a double event:
spermnuclei
synergidsdisintegrating In this slide, plasmogamy has
already occurred…but what part of syngamy has not occurred yet?
karyogamy!
no miracle-gro, no compost!
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