Transcript Zygnemataceae

Flowering Plants
Domain Eukarya
Kingdom Plantae
Phylum Anthophyta/Magnoliophyta
Life Cycle of Flowering Plants
SYNGAMY
mitosis
gametes
zygote
gametangia
differentiation
Gametophyte
1N 2N
germination
mitosis
differentiation
Sporophyte
differentiation
mitosis
germination
differentiation
sporangium
spores
mitosis
sporocyte
MEIOSIS
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.
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 internodes
The leaves appear in four whorls
stigma
locule
ovule
flower hypogynous
™ gynoecium
flower
style carpel
perfect
anther ¢
ovary
superior
pollen stamen
filament androecium
petal corolla
receptacle
pedicel
sepal
calyx
complete
perianth
Microsporogenesis: Prophase I of Meiosis
http://images.iasprr.org/lily/lpachy-m.jpg
Microsporogenesis: Late Prophase I of Meiosis
http://images.iasprr.org/lily/lepto.jpg
Microsporogenesis: Metaphase I of Meiosis
http://images.iasprr.org/lily/meta-i.jpg
Microsporogenesis: Anaphase I of Meiosis
http://images.iasprr.org/lily/anaph.jpg
Microsporogenesis: Telophase I of Meiosis
http://images.iasprr.org/lily/telo-i.jpg
Microsporogenesis: Metaphase II and Anaphase II of Meiosis
http://images.iasprr.org/lily/meta-ii.jpg
Microsporogenesis: Telophase II of Meiosis
http://images.iasprr.org/lily/telo-ii.jpg
Microsporogenesis: Meiosis complete (but prophase of mitosis)
http://images.iasprr.org/lily/tetrad.jpg
Microsporogenesis: Completed, Separated Microspores (note prophase)
http://images.iasprr.org/lily/microsp.jpg
Pollen Grain: Mitosis Makes Endosporic Microgametophyte
Pollen Wall: Microspore Wall (allergenic?)
Tube Cell
Generative Cell
Nucleus
Nucleus
Cytoplasm
Cytoplasm
The tube cell
digests a path from
the stigma to the
egg.
http://images.iasprr.org/lily/pollen2.jpg
Pollination: vectorassisted movement of the
pollen grain from the
anther to the stigma.
The generative cell
follows the path to
the egg, and
divides to make
two sperm cells.
Both participate in
syngamy.
Pollen Tube Growth
The 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.
http://bilbo.bio.purdue.edu/~cjslab/pollen-tubes.jpg
Megasporogenesis: taking place inside the ovule inside the ovary.
megasporocyte
meiosis I
4 megaspores
3 disintegrate
meiosis II
functional
megaspore
mitotic divisions without cytokinesis
megagametophyte
3 antipodals
central cell
cytokinesis
egg
2 synergids
In Flowering Plants, syngamy is a double event:
syngamy#2:
sperm
nuclei
2 x 1N polar nuclei + 1N sperm
= 3N primary endosperm cell
no miracle-gro, no compost!
syngamy#1:
1N egg + 1N sperm = 2N zygote
synergids
disintegrating
http://botit.botany.wisc.edu/courses/img/Botany_1
30/Diversity/Angiosperms/Fertilization.jpg
In this slide, plasmogamy has
already occurred…but what part
of syngamy has not occurred yet?
karyogamy!