Week 14 L5: Plant Development 3 - Pollination Flashcards
How do plants grow indeterminately?
meristem activity
What are 2 advantages of flowers for angiosperm?
Flowers protect the ovule from external stresses
Flowers attract pollinators
High levels of BR1/2 are correlated with what phenotype in arabidopsis?
fewer rosette branches
Do land plant cuticles permit photosynthetic gas exchange in open air?
NO
Predict the effects on pollen exchange due to a loss of lodicule swelling?
fewer pollen grains exchange since the florets do not open.
What does permit photosynthetic gas exchange?
the stomata, CO2 in
What does permit photosynthetic gas exchange?
the stomata, CO2 in
What are the 3 types of pollinators?
Predominant self-crosser Self-compatible Opportunistic out-crosser Self-compatible Obligate outcrosser Self-incompatible
What is a predominant self-crosser?
self-compatible as it can accept its own pollen.
Arabidopsis thaliana.
What is an opportunistic out-crosser?
self-comatible and can outcross. It is both
Soy bean
What is the obligate outcrosser?
self-incompatible
Arabidopsis lyrata
What type of arabidopsis have showy flowers?
Lyrata to attract pollinators
What is a bisexual plant?
each flower of each individual has both male and female structures, i.e. it combines both sexes in one structure. Flowers of this kind are called perfect, having both stamens and carpels.
Why do the angiosperms have to develop another way to fertilise the egg?
as the ovary is completely enclosed.
The anther at the top of the stamen is not going to result in fertilisation.
Have to rely on other mechanism as the ovary is completely enclosed.
As the pollen tubes do not initiate = need to outsource fertilisation. self-incompatible.
What is an example of a species which can have different fertilisation processes?
leavenworthia alabamica
What are the advantages of an outbreeder?
Genetic flow
Adaptability
Persistence over time
What are the disadvantages of outbreeding?
Requires at least 2 plants to colonize
Pollinators required
What are the advantages of inbreeding?
1 plant can colonize a new area
Rapid speciation
No pollinators required
Stabilizes a successful genotype
What are the disadvantages of inbreeding?
No genetic flow (BAD IF THE ENVIRO CHANGES) Adaptability lost (Have to rely on random mutation) Genetic drift (Cant get rid of random mutation without sex)
How does inbreeding cause genetic drift?
As it relies on random mutations for adaptability, if this occurs then it is hard to introduce variation through sex.
A different phenotype/species will be made.
Inbreeding depression. Accumulation of damaging traits.
What are the grasses which are selfers?
barley
wheat
rice
How do most grasses fertilise?
Self incompatible
Why would grasses be bread to self fertilise?
for stability of a phenotype
guarantee that you will get your gran, don’t have to rely on pollinator. what if the pollinator is lost?
What is the megagametophyte?
The female gametophyte that arises from a megaspore of a heterosporous plant. In angiosperms, the megagametophyte is the embryo sac.
What is the megagametophyte in angiosperms?
embryo sac
What is heterosporous?
Heterosporous forms produce two kinds of spores: microspores produced in microsporangia and megaspores within megasporangia. Microspores germinate to produce male gametophytes, while megaspores give rise to female gametophytes.
BISEXUAL
What gametophyte can double fertilisation occur in?
megagametophyte
What is a meiocyte?
type of cell that differentiates into a gamete through the process of meiosis
How does double fertilisation occur of a megagametophyte?
meiosis has occurred.
One of the meiocytes goes onto divide meiotically.
Pollen tube finally reached inside and penetrates one of the synergid cells and releases the sperm cells.
The synergid dies when it is punctured by the pollen tube.
1 sperm, fertilises the egg cell and give rise to the zygote. ZYGOTE
The other goes and combines with the polar nuclei. ENDOSPERM
What is a synergid cell?
support cell to the egg cell inside the embryo sac of flowering plants.
They work with the egg cell and the central cell accomplish double fertilisation.
means ‘working together’
Play a role in pollen tube guidance and function.
In double fertilisation, how many sperm cells are in the pollen tube?
2
When one of the sperm cells fertilise the egg cell to make a zygote, what is the chromosome count?
2n zygote
What is the chromosome count when the other sperm fertilises the polar nuclei?
3n triploid count endosperm
What is the endosperm?
the part of a seed which acts as a food store for the developing plant embryo, usually containing starch with protein and other nutrients.
What are the 2 tissues called which are fertilised in plants?
filial tissue
next generation, maternal and maternal combination.
When the polar nuclei are fertilised what do they become?
endosperm
How many synergid die when fertilisation occurs (penetration) ?
1, the surviving one is called the persistent synergid
What does an embryo go onto form?
seed
What happens if fertilisation fails?
second pollen tube come in an lead to a potential fertilisation.
What part of the plant enables the chance of a second fertilisation?
the persistent synergid
due to attraction from the persistent synergid - second chance to make a seed.
Do some plants double fertilise even though the first fertilisation was successful?
YES, many ovaries contain more than one ovule. each ovule leads to one seed.
How are persistent synergids inactivated?
the persistent synergid fuses with the endosperm. the synergid products are released into the endosperm and the endosperm nucleus breaks down
What is a successful fertilisation?
endosperm and zygote
When does endosperm nuclear elimination occur?
endosperm mitosis
Does one floret mean 1 grain?
yes, one floret = one ovule = one grain
What is a floret?
one of the flowers making up a composite flower head.
What is an example of a plant containing more than one ovary?
tomato
When would polytubey occur?
occurs when double fertilisation occurs
