Gametophyte Development And Fertilization
pollen mother cell in sporogenous tissue of anther undergoes meiosis to
form a radial quartet of haploid microspores
microspore undergoes mitosis to form a pollen grain containing a
vegetative cell and generative cell.
- The vegetative
cell is transcriptionally and metabolically active, the generative cell is
generative cell divides again to form 2 sperm cells.
Embryo Sac (megagametophyte)
megaspore mother cell within the ovule undergoes meiosis to form a linear
quartet of megaspores
monosporic development (the most common type, also known as Polygonum
type), three megaspores degenerate
surviving megaspore undergoes 3 mitotic divisions to form an 8-nucleate
cell. Cellularization produces the mature embryo sac with an egg cell, 2
synergids, a binucleate central cell and 3 antipodals.
Pollination and fertilization
pollen grain lands on the stigma of a flower and germinates, producing a
pollen tube. Germination involves active hydration of the pollen grain.
pollen tube enters the cell wall of the stigmatic (papillar) cells and
grows between cells through the style to the ovary.
- In the
ovary, the pollen tube exits the stylar tissue and grows on the surface of
the ovary cavity. It grows to an ovule and enters the micropyle.
pollen tube penetrates a synergid and ruptures, releasing the 2 sperm
synergids have regions of direct membrane contact with the egg cell and
sperm cell fuses with the egg cell membrane, allowing the nucleus to enter
the egg and fuse with the egg nucleus, forming the diploid zygote.
other sperm fuses with the central cell membrane and fuses with the 2
nuclei to form the triploid primary endosperm cell.
and species recognition (lipids)
incompatibility (gametophytic and sporophytic)
Pollen tube growth
Pollen tube guidance
from style (TTS)
mutants and pollen/style interactions
from ovules/embryo sacs
is uniparental maternal
examples of biparental and even rare cases of uniparental paternal