lecture 18, Fertilization and seed development Flashcards
Vegetative =
leading to sterile / non-gamete cells
Generative =
leading to sperm cells
Recap: gymnosperms contain..
- microsporocyte (mother cell)
- tetrad of microspores
- mature pollen grain = 4 cells
- 2x prothallial cell
- generative cell –> 1 sterile/stalk cell and 1 spermatogenous cell (–> 2 cells)
- tube cell
the difference between an angiosperm and a gymnosperm?
the mature pollen grain contains 3 cells (not 4)
- generative cell –> 2 sperm cells
- tube cell
when does pollen grain germination occur?
once the pollen is accepted by the host (female stigma)
what does the tube cell develop into?
pollen tube, which will deliver non-motile sperm cells
what does the generative cell divide into?
2 sperm cells - only occurs once pollen tube has reached micropyle
the ovule structure is made up of
integument
nucellus
female gametophyte
unlike a gymnosperm, an angiosperm contains:
- 2-3 integuments (not 1)
- pollen tube enters micropyle
definition of coenocytic:
multiple nuclear divisions but no cytokinesis; multinucleate
steps of gymnosperm fertilization:
- 4 megaspores, 1 survives
- pollination (egg cells have not formed yet)
- megaspore develops into multicellular megagametophyte
- archegonia divides into 2 egg cells
- pollen grain germinates, pollen tube enters micropyle
- sperm nucleus released
- one egg cell is fertilized by sperm
how many times does a female gametophyte undergo mitosis in angiosperms?
3 times
what do 3 rounds of mitosis within a female angiosperm gametophyte produce?
8 nuclei, 7 cells
what does double fertilization in angiosperms produce?
A 3N endosperm:
sperm #1 + egg cell
sperm #2 + 2 polar nuclei
where is the endosperm from in gymnosperms?
the female megagametophyte (n)
