Plants in their environment Flashcards
(114 cards)
1
Q
what are the steps in female angiosperm gametogenesis
A
-sporophyte (diploid)
-megaspore mother cell
meiosis
-4 megaspores (haploid)
3 degenerate
1 does mitosis 3 times
-each cell has 8 nuclei
1 forms the ovum.
2 form the female part of the triploid endosperm.
2 form synergids
3 form antipodals
2
Q
what do synergids and antipodals do
A
direct pollen tube growth and provide nutrients to the ovum.
3
Q
what are the stems in male angiosperm gametogenesis
A
-sporophyte (diploid)
-microspore mother cell
meiosis
-4 haploid microspores
mitosis twice
-each has 3 nuclei
1 forms male gamete (generative).
1 forms male part of triploid endosperm.
1 forms pollen tube (vegetative).
4
Q
what causes flowering?
A
in response to photoperiods and other conditions, the leaves send a signal to the shoot apical meristem to convert into floral meristem and start producing floral tissues.
5
Q
what are short day, long day and day neutral plants
A
short day plants require a long night to flower.
long day require a short night to flower.
in day neutral plants flowering doesn’t depend on the photoperiod.
6
Q
what is the overall male anatomy of a flower called and name each part
A
overall it is called the stamen or androecium and it is made up of the filament and anther which has four chambers where pollen is made and stored.
7
Q
what is the overall female anatomy of a flower called and name each part
A
overall it is called the pistil, carpel or gynoecium and it is made up of the stigma, style and ovary which is where ova are produced and stored.
8
Q
name the other structures in flower anatomy other than the male and female parts
A
petal/corolla
sepal/calyx
receptacle
stem/pedicel
9
Q
what are the types of pollination
A
abiotic:
wind* and water
biotic:
insects*, birds and mammals
*most common
10
Q
how are flowers adapted for pollination
A
primary attractants:
reward for visiting the flower
secondary attractants:
advertisement can be
-visual- colour, markings, shape, movement
-olfactory
t-emperature
11
Q
how do flowers visual features attract the right pollinators
A
the colours used are wavelengths that the correct pollinators can detect. sometimes UV markings are also used. Markings and shape often draw the insect to the centre of the flower where stigma, pollen and rewards are located (honey markings).
12
Q
how do flowers olfactory features attract the right pollinators
A
butterflies, bees and moths are attracted to sweet smells whereas beetles are attracted to yeasty, fruity, spicy smells.
Stapelia gigantea/ carrion flower smells like rotting meat to attract flies (putricene and cadaverine)
genes for aroma production are switched on at the times of day the correct pollinators are active (more energy efficient).
13
Q
how are odours analysed and why is this important
A
using gas chromotography mass spectrometry
knowing the type of odour you can infer the type of pollinator.
14
Q
what are two examples of flowers which utilise temperature to attract pollinators
A
arum lily- has a spadix which contains the flowers and this heats up to 10 degrees above ambient so that more volatiles are produced, so pollinators can smell them from further away.
crocus- close their petals at night and inside is warmer than outside so makes a good shelter for insects whilst also leading to pollination for the plant.
15
Q
what are the main three types of generic rewards for pollinators
A
nectar, pollen and shelter.
16
Q
what is nectar
A
sugary solution with amino acids (costly).
Found below the anther and stigma so that insects must pass these structures to reach the nectar.
evolved specifically as a reward for pollinators.
17
Q
give two examples of how co evolution can lead to there being specific rewards for specific pollinators.
A
yucca plants and tegeticula moths
figs (flowers internal) and gall wasps
both give away ovules for larvae nutrition in return for pollination. both species are dependent on each other.
18
Q
give two adaptations of pollen which allow it to increase likelihood of pollination
A
-high variation in shape including spikes
-pollina (little packets of pollen) can attach to pollinators.
19
Q
give three adaptations of floral shape which allows increased likelihood of pollination.
A
-mimicry
-long floral tubes which restrict the type of pollinator as they are adapted for beaks of birds or proboscis of butterflies
-specialised mechanisms such as triggers, traps and narcotics which don’t allow the pollinator to leave the flower unless it has made contact with pollen.
20
Q
what adaptions do abiotic wind pollinated plants have
A
-flowers do not need attractants like petals.
-stamens need to be in contact with the wind stream.
-stigmas are large so they are more likely to come into contact with pollen
-pollen is smooth as it doesn’t need to stick to pollinators but does need to be easily carried by the wind.
21
Q
what adaptions do abiotic water pollinated plants have
A
pollen needs to remain dry to protect against germination.
epihyrophily is most common- pollen floats on top of the water.
hypohydrophily is less common- pollen is underwater.
22
Q
what proportion of angiosperms are hermaphrodite
A
70%
produce both male and female gametes.
23
Q
what is it called when sex is separated between different flowers on the same plant
A
monoecy
24
Q
what is it called when sex is separate between different plants
A
dioecy
25
what are monoecy and dioecy examples of
dicliny - separating sex onto different flowers
26
what is it called when the sexes are separated within the same flower
herkogamy
27
why is it important that sex is separated either by herkogamy or dicliny
to prevent self fertilisation
28
in dioecy what features do the plants need to have for successful pollination
- male and female plants should be located within range of each other for pollination to occur
-male and female flowers should be similar, to prevent pollinators developing preference.
- need a good ratio of males to females
29
give 3 examples of dioecious plants
kiwi
date palm
avocado
30
what do breeders need to know when growing dioecious plants
they need to use genetic markers to identify from seed whether the plant is male or female. some plants take years to flower and it is important to know whether you have the right ratio of males to females.
31
give an example of a monoecious crop and describe the male and female flower
maize/corn
male-tassels
female-silks and cobs
32
how does temporal separation prevent self fertilisation in plants with herkogamy
flowering and maturation of male and female parts doesn't happen at the same time.
eg if the anther develops before the stigma then it can't fertilise itself but it can fertilise the mature stigma of a flower that flowered a bit earlier.
33
what is it called when the pistil matures before the anther
protogyny
34
what is it called when the anther matures before the pistil
protoandry
35
name the different types of biochemical incompatibility
heteromorphic and
homomorphic (homomorphic includes gametophytic and sporophytic)
36
what is heteromorphic incompatibility
when there are different flower structures within a species (each type is called a morph) which have biochemical mechanisms to make flowers of the same morph incompatible. each plant has flowers all of the same morph so that self-fertilisation is prevented. they are able to fertilise a plant with a different morph. an example of two different morphs would be flowers with long anthers and short stamens OR short anthers and long stamens.
37
what is homomorphic incompatibility
all the flowers in all the plants of the same species have the same structure but they have biochemical processes which make them incompatible with themselves. can be gametophytic or sporophytic.
38
what is gametophytic incompatibility
self incompatibility at the S locus.
diploid microspore mother cell has two S alleles eg S1 +S2. each haploid microspore with inherit either S1 or S2. the resulting pollen grains are different from each other. if they land on a stigma of the same plant (S1,S2), then neither pollen S1 or S2 will produce a pollen tube. if it lands on a different plant eg (S1, S3), the S1 pollen would not be able to produce a pollen tube but S3 would. if the genotype was completely different to the pollen type then both S1 and S2 produce a pollen tube
39
what is the difference between gametophytic and sporophytic incompatibility
sporophytic is more stringent as it doesnt allow fertilisation between close relatives whereas gametophytic does.
40
describe sporophytic incompatibility
the diploid tapetum which lines the inside of the anthers transfers proteins to the outside of the pollen which are a mixture of S1 and S2 (if the genotype of the plant is S1S2). therefore it doesn't matter whether the pollen has an S1 or S2 allele, it will not be compatible with any stigma which has a genotype containing either S1 or S2 (eg. S1S3 or S2S3) due to the presence of both proteins on each pollen grain. therefore, the pollen is only compatible with completely different genotypes eg. S3S4
41
when is it an advantage to be able to self fertilise
when there is a shortage of pollinators or environmental uncertainty.
weeds sacrifice diversity to replicate rapidly.
small populations may not have many distant relatives available to mate with and so need self-fertilisation.
42
name the different parts of the pistil during the growth of the pollen tube
stigma
secretory zone (top part of the stigma)
transmitting tissue (beneath the secretory zone)
style
pollen tube
cellulose plugs (to keep male gametes at the tip of the growing tube)
ovary
micropyle and integuments
ovules (contains ova)
43
describe the journey of a pollen grain
lots of pollen grains land on the sticky stigma and more than one germinate by absorbing water. if compatible the pollen tube grows into the secretory zone where they still may be blocked if incompatible. then they grow into the transmitting tissue until reaching the ovary (pollen tubes compete for access). chemical signals direct the tube towards the micropyle (a gap in the integuments entering into the ovary) and towards an unfertilised ovule.
44
describe how fertilisation occurs in an angiosperm
the pollen tube bursts a synergid cell as it enters the embryo sac. this causes the cell wall of the pollen tube to break down and release the 2 male gametes. one fuses with the female gamete to forma diploid zygote and the other fuses with the polar body to form a triploid endosperm which provides nutrients for the zygote.
45
what are the steps of embryogenesis
1. polar zygote
2. symmetric division leading to a small apical cell and a large basal cell
3. the basal cell becomes the suspensor which is a collection of 50-75 cells that supports the embryo.
4. the apical cell becomes the proembryo
5. the proembryo becomes the embryo which changes shape: globular, heart shaped, torpedo (forms cotyledons and shoot apical meristem).
46
what are L1 L2 and L3
the different layers of the embryo
L1 is the outermost layer-epidermis
L2 is the middle layer- ground tissue
L3 is the innermost layer- vascular tissue
47
what are segment deletion mutants
the segments of an embryo are apical, central and basal. a segment deletion mutation in when one of these segments is missing.
apical- cotyledons and shoot apical meristem
central- hypocotyl
basal- hypocotyl and roots.
48
what is a plant called if it has a mutation in the vascular, ground or epidermal tissue
a radial mutant.
49
name some differences between a monocot and dicot seed
carbohydrate endosperm in a monocot provides energy
protein/lipid cotyledon provides energy in a dicot.
50
why is the timing of embryo development important
needs to coincide with fruit ripening.
51
what are the three steps of fruit development in a tomato plant.
1. chlorophyll is broken down and carotenoids are produced, changing the colour of the fruit from green to red.
2. starch is converted into sugars so that the fruit tastes sweet.
3. pectin is broken down so that that fruit becomes soft.
52
why are fruits soft and sweet
to make them more palatable and appealing to animals who will eat them and disperse the seeds.
53
what is the specialised structure in the ovary wall and what does it differentiate into to make the fruit.
pericarp- differentiates into the exocarp (skin/rind), the mesocarp (flesh) and the endocarp (protects seed aka. stone).
54
what are the two categories of fruit and their subcategories
-fleshy or dry
-fleshy is split into simple (such as apples- develop from one ovary of a simple flower), aggregate (such as raspberries- develop from multiple ovaries of the same flower), and multiple (such as figs- develops from the ovaries of many flowers)
-dry is split into split (such as legumes) or not split (like nuts and grains).
55
why is it important for seeds to be dispersed
the new plant shouldn't grow too close to the parent plant to avoid intraspecific competition.
56
what are the different types of seed dispersal
abiotic-wind, water or mechanical
biotic- stuck in fur or carried in the GI tract
57
what adaptations do plants have to help seed dispersal by wind
light
parachutes or wings
pepper pots (like poppy seed heads)
tiny
woolly hairs
58
what adaptations do plants have to allow their seeds to be dispersed effectively by water
like pollen they germinate when they absorb water so they are kept dry by waterproof casings (like a coconut)
-air spaces help them float -waxy cuticles aid waterproofing
-water can be used to remove the seed from the fruit.
59
give two of examples of mechanical seed dispersal mechanisms
explosive capsules which spray seeds
changes in humidity causing a corkscrew motion which causes the seed to burrow into the ground
60
what adaptations do plants have to allow their seeds to be dispersed biotically
-the seeds which are carried in the GI tract usually have flashy fruit that is appealing to the animal such as colour and aroma (which repels the animal if not ripe and attracts the animal when ripe). some seeds need the mechanical damage and low pH of the GI tract in order to germinate.
-dry seeds have barbs, hooks and stickiness, to attach themselves to fur to be carried.
61
what is vivipary and give an example
when the seed isn't dispersed, they remain attached to the parent plant and start to develop as soon as they are produced. eg. mangroves.
62
what is dormancy and what can break dormancy
give an example
when a seed doesn't germinate until the correct conditions for growth are reached. conditions for breaking dormancy include:
light
humidity
cracking
temperature
removing the fruit
chemical attack
washing off growth inhibitors
eg. poppies germinate when exposed to light
63
give the steps for seed germination
1. seed absorbs water
2. embryo produces gibberellic acid
3. stimulates aleurone layer to produce amylase
4. amylase breaks down starch in the endosperm
5. sugar is used by the embryo for growth.
6. radicle (root) emerges to anchor the plant
7. hypocotyl grows upwards (cotyledons remain folded in an apical hook to protect them)
8. emergence from the soil into light causes hypocotyl to stop elongating and chlorophyll starts to be synthesised.
9. cotyledons unfold and apical meristem starts making leaves.
64
describe the structure and function of the shoot apical meristem
the top layer has the central zone (always proliferative) with peripheral zones either side (where leaves grow from). then underneath this layer is the rib meristem
65
what are the clv, wus and stm loss of function mutants
clv- broad and tall shoot apical meristem
shows that there is too many meristem cells
shows that this gene restricts proliferation.
wus- flat shoot apical meristem
meristem cells have been lost to differentiation. shows that this gene stops unwanted differentiation.
stm- absent shoot apical meristem
this shows that this gene promotes cell proliferation.
66
what is the difference between adaptation and acclimation
adaptation is the morphological or physiological change in a species or population, made in response to long term environmental pressures. acclimation is the morphological and physiological changes in an individual, made in response to short term changes in environmental conditions.
67
what is the consequence of a plant being under high light stress
photoinhibition occurs. this is where photosynthesis is inhibited due to excess light because electrons from photolysis cant replace the electrons lost from the reaction centre of PSII as quickly as they are being lost and so eventually it breaks.
68
what happens to the PSII reaction centre when it breaks and how is it fixed
the protein complex is disassembled and D1 (the broken protein) is taken out and replaced.
69
when is it classed as photoinhibition
when the rate of damage to the complex is higher than the rate of repair.
70
why does response to light need to rapid
short term changes in light levels such as sun flecks happen very quickly so if this light is to be used for photosynthesis the plant needs to respond quickly.
71
what are the rapid short term responses to light
non-photochemical quenching
LHCII migration
chloroplast movement
leaf movement
72
what is non-photochemical quenching
depending on the light levels accessory pigments such as zeaxanthin can be in different forms which can each dissipate different amounts of energy as heat so that it cant be used for photosynthesis, therefore preventing photoinhibition.
zeaxanthin is best at dissipating energy whereas antheraxanthin and violaxanthin are less effective.
73
how does LHCII (light harvesting complex II) migration lead to reduction in photoinhibition
D1+D2 proteins are part of the PSII reaction centre protein complex. these are not covalently bound to LHCII, so it can dissociate from the complex and migrate away. when it migrates away this reduces the amount of light delivered to the reaction centre for photosynthesis (and therefore prevents photoinhibition).
74
how does chloroplast movement reduce photoinhibition
in high light intensity, chloroplasts move to the edges of the cells so they shade each other.
75
how do leaf movements reduce photoinhibition
in response to high light intensity, the leaves can fold so that they create their own shade and less surface area is exposed to high light.
76
in what way can a plant acclimate (medium term response) to different light levels
using sun and shade leaves. the leaves on the same plant have different features depending on the amount of light they are exposed to. sun leaves are exposed to most sun and are commonly facing outwards. shade leaves are exposed to less light and are found on the inside of the plant.
77
give the main features of sun leaves
-thicker because light can penetrate further
-lower surface area to prevent photoinhibition
-more RuBISCO for faster photosynthesis
- more xanthophylls for photochemical quenching.
78
what are the features of shade leaves
-thinner (as light cant penetrate as far)
- higher surface area to capture more light
-more chlorophyll so that as mush light is absorbed as possible
79
what is it called when describing the 'extent to which a plant can produce sun and shade leaves'.
plasticity
80
what adaptations (long term response) can a plant have for high light intensity
hairy leaves (white hairs reflect light away from the leaf)
beach grass has curled up leaves and invaginations with hairs to prevent transpiration by thickening the boundary layer. it also has a thick waxy cuticle. high light often comes with high temperatures
81
what adaptations (long term response) can a plant have for low light intensity
red underside of leaves - reflects light back up through the leaf so that it is used for photosynthesis twice.
holes in leaves so that the leaf can extend into a wider range so it is more likely to come into contact with sunflecks.
82
how does a plant respond to drought conditions (water stress)
abscisic acid (ABA) a plant hormone is released which causes stomatal closure to reduce transpiration and conserve water.
83
how are stomata opened and closed
K+ is pumped into guard cells and water moves in by osmosis causing them to become turgid and this opens pore. ABA binds to receptors on guard cells. causes K+ to be pumped back out and inhibits it from being pumped in. that stomata close.
84
where is water stress sensed and where is ABA made
water deficit is sensed in the roots and ABA is made in the roots and then travels in the xylem to the leaves.
85
what is partial root zone drying (PRD) irrigation and why is it useful
you place each half of the roots in a different ditch. each side is alternately watered. the side that is not watered makes ABA that goes around the whole plant to close stomata and prevent transpiration. this makes the water usage more efficient.
86
what causes salt stress and how does it impact the land
over irrigation and poor drainage
causes permanent damage to the land and currently 20% (45 million hectares) of land is suffering from salt stress
87
what is physiological drought
when even if there is water present, due to the high salt content the plant responds as if there is a drought because water moves out of the plants by osmosis
88
what are the toxic effects of salt on the plant
can impact nutrient uptake.
can cause proteins to denature.
89
what is osmotic adjustment and what does it entail
it is the plants response to physiological drought.
in order for water to move into the plant, the osmotic potential of the cells needs to be increased above that of the soil. however inorganic ions cant be accumulated as this denatures proteins so non-charged, soluble, organic macromolecules are used instead which don't interfere with the hydration shell of proteins or with metabolism.
90
what is the hydration shell of a protein
the outer r groups of amino acids of a protein are hydrophilic and attract water molecules to form a shell which stabilises the protein.
91
what adaptations do plants have to cope with high salt conditions and give examples of a plant with these.
mangroves have salt glands which pump salt out of the leaves.
quinoa has salt bladders on the outside of the leaves which salt is pumped into.
92
what are the 2 mechanisms of nutrient acquisition in plants
- nutrient acquisition by bulk flow due to negative pressure from transpiration pulls water with dissolved nutrients into the roots.
- nutrient acquisition by diffusion of nutrients from the soil to the roots
93
what is bulk flow limited by
the concentration of the nutrient in the soil
94
what forms around the root once the nutrient has run out
nutrient depletion zone
95
what does the size of the nutrient depletion zone depend on
the solubility of the nutrient (how far in can travel through the soil to reach the roots)
96
give an example of a nutrient with a small nutrient depletion zone
phosphate due to its low solubility.
97
how is the challenge of nutrient depletion zones resolved
using mycorrhizal associations which extends nutrient harvesting range and the area of nutrient depletion zones.
98
what kind of relationship is a mycorrhizal association
symbiotic/mutualism- the fungi are fed carbon compounds by the plant and the fungi provide the plant with nutrients
99
what are the two types of mycorrhizae and which is more common
ectomycorrhizae 2%
arbuscular mycorrhizae 73%
some plants can switch between but this is unlikely
100
what is arbuscular mycorrhizae
highly branched hyphae that explore the soil (high variation in distances travelled). they penetrate the epidermis of the root and colonise the cortex (do not pass the casparian strip to control what enters the xylem). they form different structures inside the cells but both organisms keep their cell walls intact (cortex cells invaginate around the hyphae). this is to control what is coming into the plant from the environment.
101
what 3 structures can arbuscular mycorrhizae form inside cortical cells
arbuscules
vesicles
hyphal coils
these are the sites of nutrient and sugar exchange.
102
what is ectomycorrhizae
hyphae form a thick mantle that coats the roots. hyphae penetrate between cortical cells to form the hartig net.
103
what is the ratio of root cells to fungi in plants with ectomycorrhizae
mantle is so thick that root hair cells cant be formed, so the mycelium takes over this role. this means fungal biomass is higher than root biomass in most cases.
104
why do orchid seeds need to make mycorrhizal associations to germinate
they are really tiny and light because they are dispersed in the wind. this means that they dont contain any energy stores. they rely on species specific micorrhizal associations to provide them with carbon compounds and nutrients (altruism from fungi as they get nothing in return until the plant starts photosynthesising).
105
what is the impact of agriculture on mycelium
ploughing can destroy mycelial networks which reduces crop yield.
fungi can now be added to the soil to improve yield.
106
why does flooded paddy rice not use mycorrhizae when upland paddy rice does.
anaerobic conditions in water- most fungi are aerobic. additionally it is easier for nutrients in water to diffuse towards the roots than in soil.
107
what is the equation for nitrogen fixation and what enzyme is used
N2 +3H2 -> 2NH3
nitrogenase and ATP
108
where are the enzymes required for nitrogen fixation found
only in bacteria
109
where are nitrogen fixing bacteria found
free living in the soil or in root nodules (in symbiotic association)
110
what is an example of a plant and bacteria symbiotic association
legumes and rhizobium.
plants re provided with nitrogen and bacteria are provided with carbon and a home in the nodules
111
what is the purpose of leghaemoglobins found in root nodules
nodules have anaerobic conditions for nitrogenase activity but enough oxygen for respiration. this is regulated by leghaemoglobins which have a very high affinity for oxygen
112
what are the genes expressed by the legume plant to form nodules
nodulin genes
113
what are the genes expressed by the rhizobium bacteria to form nodules
nodulation (nod) genes
114
how does nodule formation occur
1. in low N2 roots secrete flavenoids into the rhizosphere.
2. this attracts rhizobium and nod genes are switched on
3. nod gene products cause root hairs to curl around clusters of rhizobium and cause cell wall to break down, so they can enter the cells.
4. the golgi fuses into an infection thread that the bacteria travel in (for compartmentalisation).
5. secondary infection threads form throughout the intercellular space of the cortex.
6. rhizobium produce chemicals which stimulate cell division of cortical cells to produce the nodule.
7. once the nodule has developed the bacteria become bacteroids which enter nitrogen fixing phase.
