4.2 plant reproduction Flashcards
1
Q
what are the 4 whorls of a flower?
A
calyx
corolla
androecium (stamen)
gynoecium (pistil)
2
Q
label a flower
A
refer to sheet
3
Q
what does protandry mean?
what does protogyny mean?
A
stamen ripens first
stigma ripens first
4
Q
what parts are involved in the pistil? (3)
A
stigma
style
ovary
5
Q
what parts are involved in the stamen?
A
anther and filament
6
Q
what is the function of the sepals?
A
protect the flower while it’s still forming and before the flower bud opens
7
Q
what type of plants have sepals? what type don’t?
A
dicotyledons do
monocotyledons don’t
8
Q
what is the function of the nectary?
A
produces nectar which is sweet and attracts insects
9
Q
what is the function of the petals?
A
large, colourful and patterned to attract insects
10
Q
what is the function of the anther?
A
male reproductive organ to produce male gametes via meiosis and mitosis
11
Q
what is the function of the filament?
A
a stalk that supports the anther and carries water and nutrients to the anther in the vascular bundle
12
Q
what is the function of the stigma?
A
a sticky surface that pollen grains land on during pollination
13
Q
what is pollination?
A
the transfer of pollen grains from the anther to the stigma
14
Q
what are the 4 types of pollination?
A
self and cross
wind and insect
15
Q
what is self pollination?
A
pollen falls from there anther to stigma of the same flower
16
Q
what is cross pollination?
A
pollen is transferred from anthers of one flower to the stigmas of a different flower of the same species
17
Q
what are the advantages of self pollination? (3)
A
- not dependent on pollinating agents
- if a given genotype is well suited for an environment, self pollination helps to keep this trait stable in the species
- number of flowers are small or widely spread
18
Q
what are the disadvantages of self pollination? (3)
A
- lack of variation so no adaptations to the changing environment/pathogens
- can lead to inbreeding depression or the reduced health of the species
- genetic defects in self pollinating plants cannot be eliminated
19
Q
what are the advantages of cross pollination? (3)
A
- increases the variation in the offspring after genetic recombination
- increases adaptability to the offspring to environmental changes
- gives plants protection against pathogens
20
Q
what are the disadvantages of cross pollination? (3)
A
- requires a pollinating agent - insect, bird or wind
- require plant to produce structures to attract pollinators
- not suitable where numbers of flowers are small or widely spaced
21
Q
how do plants reduce self pollination? (4)
A
- the stamen and stigma ripen at different times of the year
- the anthers are below the stigmas so the pollen cannot fall on it
- separate male and female flowers (on the same plant)
- chemical self incompatibility
22
Q
what is chemical self incompatibility?
A
pollen cannot germinate on the stigma of the flower which produced it
23
Q
what are the characteristics of wind pollinated flowers? (6)
A
- petals usually absent or small, green and inconspicuous
- no scent or nectar
- anthers hanging outside the flower so the pollen can catch the wind
- large feathery stigmas hanging outside the flower
- lots of smooth light pollen that can be easily blown (large SA)
24
Q
give some examples of wind pollinated flowers
A
wheat
rice
corn
barley
25
what are the characteristics of insect pollinated flowers? (6)
- colourful petals sometimes with nectar guides
- scent or nectar
- produced smaller pollen grains
- anthers and stigma within the flower
- small quantities of sticky, sculptured pollen produced
26
give some examples of insect pollinated flowers
rose
sunflower
orchids
lilies
27
what is the 3 step process in order to get to a pollen grain?
- microspore mother cell divides by meiosis
- formed a tetrad of 4 haploid cells
- this divides by mitosis to form a pollen grain
28
what are the 2 layers to the cell wall of a pollen grain and describe them?
exile - thick outer wall made of long lasting tough waterproof substance
intine - thinner and more porous inner wall
29
what is the exile adapted to do?
help the pollen be transported from the anther to the stigma - the pits in the surface enable gaseous exchange
30
what are the names of the 2 nuclei?
what does each do?
generative - divides again by mitosis to produce 2 identical male gametes
tube - controls growth of the pollen tube following pollination - guides it down the style into the micropyle
31
what is the layer of cells surrounding the anther called?
what do they do?
what are the characteristics of it?
tapetum
provides nutrients and regulatory molecules to the developing grains
tough and resistant to chemicals
32
what is the tapetum also resistant to? (2)
- desiccation which is necessary as pollen travels high in the air during pollination
- penetration from UV light so the DNA is protected from mutations
33
what does the fibrous layer of the anther do?
prevent dehiscence
34
what is dehiscence?
the pollen is mature and the anthers outer layers dry out which causes tension = the pollen sacs burst exposing the pollen grains into the air
35
in short terms, what is the process of ovule development?
- the megaspore mother cell undergoes meiosis to form 4 haploid megaspore cells
- 3 of these cells disintegrate and 1 undergoes 3 rounds of mitosis to produce 8 haploid nuclei
- 2 haploid fuse to form one diploid nucleus called the polar nucleus
36
what is the role of antipodal cells?
play a role in embryo nutrition as seeds germinate into seedlings
37
in short terms, describe the process of double fertilisation
- the pollen grain germinates to produce a pollen tube and at the tip if a male tube nucleus
- as the pollen tube grows the generative nucleus undergoes mitosis to form 2 sperm nuclei
- the pollen tube enters the embryo sac via the micropyle
- the tube nucleus disintegrates
- the tip of the tube opens to release the 2 sperm nuclei
38
what is the role of the tube nucleus?
tube - controls the growth of the pollen tube
39
what does the pollen tube grow against and where does it go?
against a gradient of chemo attractants from the ovules and digest its way down the style into the micropyle
40
in a summary what is double fertilisation?
(__ + __ = __)
sperm nucleus + polar nucleus = triploid endosperm nucleus
sperm nucleus + egg cell nucleus = diploid zygote
41
what does seed dispersal reduce?
what does this increase?
what does this allow?
reduces competition following germination
increases chance of growth into mature plants
allows the colonisation of new habitats
42
how are the dispersal of seeds done? (5)
- wind
- animals
- water
- bursting
- humans
43
what do dormant seeds have?
a very low metabolic rate
44
why is the testa important in a seeds survival?
chemically resistant to allow seeds to survive adverse chemical conditions
45
what do the cotyledons provide to the endosperm? until when?
nutrients until germination when the seedling will photosynthesise
46
what develops into a seed?
a fertilised ovule
47
how is an embryo formed?
within the seed the diploid zygote divides by mitosis to become the embryo
48
what 3 parts does the embryo consist of?
plumule - developing shoot
radicle - developing root
1/2 cotyledons - seed leaves
49
label the parts of the seed
testa
micropyle
funicle
endosperm tissue
ovary wall
50
what is the testa?
the outer integument dries out to form a hard waterproof seed coat (after fertilisation)
51
what is the micropyle?
a pore in the seed
52
what is the funicle?
what does it attach to?
a stalk that attaches the ovule to the placenta
it attaches to the hilium and once the funicle detaches the scar of the hilum is still visible
53
how is the endosperm tissue formed? why is it important?
the triploid endosperm nucleus undergoes multiple rounds of mitosis to then become the endosperm tissue - it provides the embryo with essential nutrients
54
what does the ovary wall become?
it matures and becomes the fruit enclosing the seeds
55
define germination
the biochemical and physiological process through which a seed becomes a photosynthesising plant
56
what are the requirements for successful germination and why? (4)
suitable temperature - enzymes work best at their optimum
water - to mobilise enzymes
oxygen - for aerobic respiration
light/dark - depends which species
57
give an example of a non endospermic seed
broad bean - dicotyledon
58
in short term, describe germination in non endospermic seeds
- imbibing
- the cotyledons swell
- the testa splits to allow entry for more O2 for aerobic respiration
- starch and proteins from the cotyledons are mobilised through hydrolysis into soluble products
59
what is imbibing?
when the seed absorbs water through the micropyle
60
give an example of an endospermic seed
maize - monocotyledon
61
in short term, describe germination in endospermic seeds
- following imbibition of water, gibberellin is released by the embryo
- it issues to the aleurone layer which contains proteins
- switches on genes to synthesise amylase and protease
- the AA produced in the layer are used in the synthesis of amylase
- amylase diffuses from layer to endosperm to hydrolyse starch
- the maltose + glucose produced diffuse into the radically and plumule
- they're used in aerobic respiration and growth in the embryo
62
what is gibberellin?
a plant growth regulator
63
what does aerobic respiration do?
releases energy from sugars and amino acids to synthesise new proteins
64
what happens to the soluble products of digestion?
transported to the embryo and carried in the phloem to the apical meristems of the plumule and radicle
