Plant Reproduction Flashcards
flowers have _ whorls. all whorls are attached by a _
4 whorls.
attached by a receptacle.
describe the differences in floral organ numbers:
- complete
- incomplete
- carpellate
- staminate
- inflorescences
- complete-has all four whorls
- incomplete-missing 1 or more whorls
- carpellate flower-female only
- staminate flower-male only
- inflorescences-clusters of flowers (as opposed to single flower)
flowers vary in
shape, size, colour, odour, whorl arrangements, time of opening.
inside carpel is _, inside that is _
inside carpel is ovule, inside ovule is megasporangium.
flowers aid in
pollination
wind pollinated flowers release:
lots of smaller pollen grains.
animal/insect pollinated flowers reward the pollinator with
food (nectar)
describe how natural selection helps increase pollination
(two ways)
- natural selection will increase selective pressure for floral traits that make it more prized to the pollinator (more likely for pollination)
- the animal pollinator will also evolve to be better able to get the prized nectar (we call this co-evolution).
what is gametogenesis? what process does it involve?
developement of gametes via mitosis.
1n gametophytes > 1n gametes
describe sporogenesis, what process does it involve?
development of mega/micro spores via meiosis.
2n sporophyte > 1n spores.
describe the steps of male gametophyte devlopment (within pollen grains)
1) contained within the anther is the microsporangium (pollen sac 2n)
2) within the microsporangium, microsporocytes undergo meiosis to produce microspores (n)
3) each microspore will develop into the pollen grain, containing the sporophytic exine (2n), and the male gametophyte (n)
4) the male gametophyte contains the generative cell, which will undergo mitosis to produce 2 sperm during pollination
5) the tube cell will eventually produce the pollen tube for fertilization
climate change can affect the _ and _ of pollen grains
viability (ability to work properly) and fertility of the pollen grains.
high temperatures can induce _ within the anthers
apoptosis
describe the steps of female gametophyte development
1) carpels contain ovules, which contain the megasporangium (2n).
2) the megasporangium contains the megasporocyte (2n), which undergoes meiosis to produce one surviving megaspore.
3) two integuments (2n) will develop and surround the ovule, eventually becoming the seed coat
4) the megaspore will undergo mitosis 3 times (without cytokinesis) to produce a 8 nuclei embryo sac (female gametophyte)
5) the plant hormone auxin will determine the fate of each cell in the female gametophyte
6) at the micropylar end 1 egg cell and 2 synergids are formed
7) at the opposite end, 3 antipodal cells are formed
8) the last two nuclei become the polar nuclei, which will be used in the endosperm production.
what’s the space between the integuments called? what happens here?
the micropyle, sperm enters here.
what plant hormone determines the fate of each cell in the female gametophyte?
the plant hormone auxin.
describe the steps of pollination
- microsporangium will break open, releasing the pollen grains for dispersal.
- the pollen grain is carried to the stigma of the carpel, where it absorbs water and germinates its pollen tube.
- as the pollen tube elongates down the style, the generative cell divides by mitosis, producing the two sperm.
- the tube nucleus then carries two sperm cells through the pollen tube to the female gametophyte (lead by chemicals secreted by the synergids).
describe what happens in double fertilisation
- fertisilation occurs when one of the sperm cells fuses with the egg cell.
- the second sperm continues past the egg cell into the central cell, where it combines with the 2 polar nuclei, forming a 3n endosperm.
- this ensures that only fertilized ovules have a food supply for the developing embryo.
if the first fertilization of the egg cell doesn’t occur, there will be no second fertilization (no endosperm food supply).
describe the steps of endosperm development
- after double fertilization the triploid (3n) nucleus divides by mitosis into a super cell that has a milky consistency (think coconut “milk”)
- after cytokinesis partitions the nuclei, the endosperm becomes solid (think coconut ‘meat’)
- endosperm is an important food source (popcorn, rice, wheat).
what does the terminal cell, and basal cell become in embryo development
- terminal cell - becomes the embryo
- basal cell -produces a thread of cells called the suspensor
what does the suspensor in embryo development do?
it anchors the embryo to the parent plant and transfers nutrients.
how many cotyledons do eudicots vs monocots have
- eudicots-2
- monocots-1
between the cotyledons are the shoot apex and root apex, which are…
meristems that will produce the shoots and roots after germination
the last stage of seed development after embryo development is? what happens in this stage?
dehydration, where water content will reduce to 5-15% seed weight
(so there’s no mould)
