chapter 16 plant responses Flashcards
1
Q
what are the 2 key limitations of plants
A
they are rooted/not mobile and they do not have rapidly responding nervous systems
2
Q
how can chemicals/hormones be transported throughout a plant
A
through the transport vessels and cell to cell
3
Q
What are plant hormones?
A
Plant hormones are signalling molecules that enable plants to respond to changes in the environment.
4
Q
plant hormones are produced in one region of a plant and have an effect in….
A
another part of the plant
5
Q
what can be added to a plant to inhibit the production of gibberellins
A
biosynthesis inibitors
6
Q
Plant hormones enable plants to…
A
access resources such as light, minerals, and water.
avoid abiotic stress.
avoid being eaten by predators.
7
Q
what type of cells cannot produce gibberellins
A
mutant seeds, they dont germinate unless ga are externally applied
they have nonworking allelsfor the genes that allow gibberellin synthesis
8
Q
ABA is also known as
A
abscisic acid
9
Q
what does aba do: maintains….. of …. and …
A
maintains dormancy of seeds and buds
10
Q
what does aba do: stimulates …. ….. responses and eg
A
stimulates cold protective responses eg antifreeze production
11
Q
what does aba do: stimulates ……. closing
A
stimulates stomatal closing
12
Q
what idoes aba have an inverse relationship with
A
gibberellins
a transcription protein is upregulated by aba and downgraded by ga > regulation loop and balance
13
Q
what does ethene do: causes…
A
causes fruit ripening
14
Q
what does ethene do: promotes …… in ….. trees
A
promotes abscission in deciduous tress
15
Q
what is abscission
A
leaf fall
16
Q
what do auxins do: control …… …..
A
control cell elonglation
by the conc of auxin
17
Q
what do auxins do: prevent …
A
prevent abscission
18
Q
what do auxins do: maintain …… dominance
A
maintain apical dominance
19
Q
what do auxins do: involved in ……
A
involved in tropisms
20
Q
what do auxins do: stimulate the release of
A
ethene
21
Q
what do auxins do: involved in fruit
A
ripening
22
Q
what do gibberellins do: cause stem….
A
elongation
23
Q
what do gibberellins do: trigger the mobilisation of food stores in ……
A
a seed at germination
24
Q
what do gibberellins do: stimulate …… …… growth in fertilisation
A
stimulate pollen tube growth in fertilisation
25
Which plant hormone has a role in stem elongation, stomatal closure, and seed germination?
gibberellins
stomatal closure (stimulates it)
26
the growth and form of a plant are the result of the interaction of many different ....... and ........ factors
hormonal and environmental factoes
27
why are scientists still unsure about the details of many plant responses
plant hormones work at very low concs so isolating and measuring changes in concs is not easy
the multiple interactions between different chemical control systems also makes it difficult to isolate the role of a single chemical in a specific response
28
what is the first plant hormone involved in seed germination and how is it activated
when the seed absorbs water the embryo is activated and begins to produce GIBBERELLINS
29
in seed germination what do gibberellins stimulate
the production of enzymes that break down the food stores in the seed
(cotyledons in dicot seeds and endosperm in monocot seeds)
30
in seed germination what happens to the food stores that are broken down
the embryo plant uses them to produce atp (to make things) for growth and then break out through the seed coat
31
evidence suggests that in seed germination gibberellins switch on genes which code for ......
amylases and proteases the digestive enzymes required for germination (amylase, maltase)
32
evidence suggests that in seed germination ABA acts as an ....... to ....... and therefore seed germination is determined by
aba acts as an antagonist to gibberellins and that it is the relative levels of both hormones which determine when a seeds will germinate
33
where is the food store in dicots and monocots
dicots: in the cotyledons (seed leaves)
moncots: in the endosperm
34
eg of an auxin
IAA (indoleacetic acid) growth stimulants produced in plants, small amount = big effect
35
where are auxins synthesised
in the tip of roots and shoots and in the meristems
in the zone of cell division
36
what type of cells are in the meristems
undifferentiated (meristematic cells)
they are similar to stem cells in humans
37
what are the 3 types of meristematic tissues/meristems
apical (at the tips: roots and shoot)
intercalary (at the middle (only in monocot stems at the base of the nodes and leaf blades
lateral (at the sides)
38
can auxins move around the plant?
they can move down the stem and up the root in transport tissue and from cell to cell
39
the effect of auxin depends on .......... and ........
its conc and interactions it has with other hormones
40
evidence suggest auxins affect the ..... of the cell wall- presence =
plasticity of the cell wall- presence = cw stretches more easily
41
how do auxins play a role in the cell wall of a plant cell becoming rigid
auxin molecules diffuse into zone of cell elongation and bind to specific receptor sites in the plant cell membrane, causing a fall in pH (to 5), this is optimum for enzymes which keep cw flexible and plastic, as cell matures auxin (and moves away from meristem) is DESTROYED, so pH rises again and the enzymes become inactive = rigid cw + fixed in shape and size so no more cell elongation
42
auxins stimulate the growth of ....
the main apical shoot
43
how do auxins stimulate the growth of the main apical shoot (what is the process)
auxins bind to receptors in cell membrane
causes a fall in pH to 5 (opt pH for enzymes that keep cw flexible > growth
however:
cells mature and move away from meristem > auxins destroyed.
pH rises and inhibits enzymes that were keeping cw flexible. cw is inflexible and rigid > cell size is fixed.
44
high concentrations of auxins supress the growth of .......... which results in
lateral shoots resulting in apical dominance
45
further down the stem the auxin con is ....... so the lateral shoots grow ......
auxin conc is lower so lateral shoots grow more strongly
46
explaining apical dominance what happens to the lateral shoots if a) apical shoot is removed b) artificial auxin is applied to a cut surface of an apical meristem
a) auxin producing cells are removed so lateral shoots grow strongly as they are freed from apical dominance
b) apical dominance is reasserted and lateral shoot growth is repressed
47
low conc of auxin promotes .....
root growth (and lateral shoot growth)
48
the more auxin that reaches the roots the more they ..... (up to a certain point)
so if a source of auxin is removed (trim stem) what happens?
grow
the translocation of auxin to the roots is removed so the growth of roots is reduced
49
what happens to root growth if the apical shoot is removed
the amount of auxin reaching the roots is greatly reduced and so root growth slows and stops
50
high auxin concentrations also inhibit ... elongation but instead enhances.....
root
branching root formation
51
gibberellins affect the length of the ... - the regions between the leaves on a stem
internodes
52
plants that have short stems produce many or few gibberellins
few or none
53
without gibberellins the plant stems are ...... this also reduces ..... and makes the plant less vulnerable to
but what is the advantage of this/experimental evidence
without gibberellins the plant stems are much SHORTER (no internodes) , also reduces WASTE and less vulnerable to DAMAGE BY WEATHER AND HARVESTING
semidwarf rice (IR8), you get the same yield so breed the mutated one and you get more crops per year. less stalk means less energy wasted
54
what is meant by synergism
when plant hormones work together/complementary to produce a greater response then they wouldve individually
magnifying the response
55
what is meant by antagonism
if the substances have opposite effects eg one promotes one inhibits growth
56
what is thigmotropism
spiraling around something eg sweetpeas around a cane wmt they dont have a need for lignin
57
what is helicotropism
diurnal motion of seasonal motion of plant parts in response to the direction of the sun
eg turning of sunflower
58
why do seasonal changes have a big affect on the amount of photosynthesis possible
because light and temperature change with the seasons and they have an affect on photosynthesis
59
why do deciduous trees lose their leaves and become dormant
if the trees had leaves on then they would be more likely to be damaged or blown over by winter gales
the rate of photosynthesis is too low, to meet this demand they hibernate and lose their leaves
60
contrast plant and animal hormones on 4 points
Plant hormones can be produced in many plant tissues, while animal hormones are only produced in endocrine and exocrine glands.
Plant hormones are transported from cell to cell, while animal hormones are only transported inside the bloodstream.
Plant hormones act on most cells, while animal hormones only act on specific cells.
The response triggered by plant hormones is slower than the response triggered by animal hormones.
61
glucose balance causing leaf loss
when the amount of glucose REQUIRED for resp to maintain leaves and produce chemicals from chlorophyll to protect against freezing is GREATER than the amount of glucose produced by photosynthesis
62
what is photoperiodism and what are the responses plants could take
the discovery that plants are sensitive to a lack of light in their environment
loss of leaves
breaking of leaf bud dormancy
timing of flowering
tuber formation for overwintering (POTATO)
63
what plant responses are affected by the photoperiod
timing of flowering in a plant, when tubers are formed in prep for overwintering, breaking dormancy of leaf buds so they open
64
what is the light sensitive pigment which exists in the forms Pr and Pfr
phytochrome
each abosrbs a different type of light and the ratio depends of the levels of light, this results in the sensitivity of plants to day length
65
what triggers absiccion and a period of dormancy
the lengthening of the dark period
66
the falling in light levels results in the falling conc of which plant hormone
auxin
67
how do leaves respond to the falling of auxin conc
producing ethene
68
what is the region called at the base of the lead stalk and what is special about it
the abscission zone and it is made up of two layers of cells sensitive to ethene
69
how does ethene affect the cell walls of the cells in the outer layer of the abscission zone/separation layer during abscission
ethene initiates gene switching in these cells = production of enzymes which digest and weaken the cells walls
70
what happens to the vascular bundles in the petioles and fatty material in abscission
they are sealed off and the fatty material is deposited in the cell on the stem side of the separation layer forming a protective/waterproof layer when the leaf falls, preventing the entry of pathogens
71
what do cells in the protective layer of the abscission zone make and why
suberin and lignin to waterproof and protect the scar when the leaf falls off
72
how do cells deep in the separation zone respond to hormonal cues during abscission
they retain water and swell putting more strain on the outer layer, they burst and make the leaf fall off.
73
how have cells adapted to lower the freezing point of the cell
cytoplasm of plant cells and sap in the vacuole contain solutes which lower the freezing point
74
some plants produce .......... which act as antifreeze and what stimulates them to do this
sugars, polysaccharides, amino acids (lower melting point of water and prevent freezing)
genes are switched on due to prolonged fall in temp and reduction in daylight
ice crystals destroy cell membranes > plant death
75
what changes take place within the plant which make it able to withstand frosty conditions (dna level)
genes are suppressed and activated
76
opening stomata allows the plant to ...... and water .....
allows the plant to cool as water evaporated from the cells in the leaves in transpiration
closing stomata conserves water
77
stomatal control in response to abiotic stresses is largely under control of which hormone and what happens
ABA
leaves release ABA under abiotic stress causing stomatal closure
78
how else can ABA cause stomatal closure (hint roots)
low soil water levels/transpiration under threat= roots produce ABA, transported to leaves, binds to receptors on plasma mem of guard cells .
aba activates ionic conc changes of the guard cells reducing wp and turgor (become flaccid) = close stomata
79
how does aba cause stomatal opening
osmosis of water into guard cell as the wp is lowered as k+ go in.
increase in turgor pressure so stomata open
80
in experiments seeds can be grown hydroponically in serial dilutions of different hormones what does this mean
in nutrient solution rather than soil
81
when investigating plant hormones why is it important to make serial dilutions
to observe the effects of different conc of hormones as they can have differenr effects on growth at different concs
82
how can standard deviation be used when investigating plant hormones
the experiments usually involve large numbers of plants, the spread of data from each experimental group should be measured using standard deviation
83
what is herbivory
the process by which herbivores eat plants
84
what are some physical defences that plants have in response to herbivory
thorns, spiny leaves, fibrous and inedible tissue, stings, hairy leaves, spikes
protect themselves and discourage herbivores from eating them
85
what are the 4 chemical defences that plants have in response to herbivory
tannins, alkaloids, terpenoids, pheromones
86
what are tannins and how do they work
make up 50% of the dry weight of the leaves
bitter tasting which puts animals off eating the leaves
toxic to insects, bind to digestive enzymes in saliva and inactivate them
87
tannins can be found highly in
tea and red wine
88
eg of alkaloids
caffeine, nicotine, morphine, cocaine
89
how do alkaloids work
very bitter tasting, large group of nitrogenous compounds, many act as drugs affecting metabolism of the herbivore and sometimes poisoning them
90
how does caffeine work to protect the plant
toxic to fungi and insects, spreads through the soil and prevents germination of other seeds of plants - protects against herbivores and plant rivals
91
how does nicotine work to protect the plant
toxin produced in the roots of tobacco plants, transported to the leaves and stored in vacuoles to be released when the leaf is eaten
its a chemical defence that is toxic and causes leaf-eating herbivores to die.
92
What type of chemical makes it harder for herbivores to eat plants?
pheromones
93
eg of terpenoids
pyrethin, citronella
94
terpenpoids often form ..... but also act as ...... to insects and fungi that might attack the plant
essential oils, toxins
they are metabolites involved in physiological processes
95
how does pyrethin work
produced by chrysanthemums acts as an insect neurotoxin interferring with the nervous system
96
what does citronella do
repels insects, it is produced by lemon grass
97
what is a pheromone
chemical made by an organism which affects the social behaviour of other members of the same species
98
how do plants use pheromones in response to herbivory eg maple tree
if a maple tree is attacked by insects it releases a pheromone which absorbed by leaves on nearby branches making them produce chemicals eg callose to protect them if they are attacked
this response can also occur on nearby plants
callose makes the leaves harder to eat
99
plants also produce VOCs which work like pheromones they stand for
volatile organic compounds
100
how do VOCs work in response to herbivory
they attract the predators of the pest organism and act as a pheromone so that nearby plants can also begin to produce the VOC before they are attacked
101
how does mimosa pudica respond to herbivory
it folds in response to touch to frighten off larger herbivores and dislodge small insects on the leaves
has toxic alkaloid and sharp prickles on the stem
leaf recovers over 10-12 mins as a result of Pions into speciic cells and then water movement
102
what is pulvinus
specialised organ that enable leaf movement
103
what is a tropism
a plant growth response to one stimuli from one direction
Tropism is when part of a plant has a directional growth response to a stimulus.
104
what is geotropism
the response to gravity
105
what is photostopism
the response to light which comes from one direction only
106
eg of geotropism
roots grow downwards into the soil in order to provide support, water and minerals
roots are positively geotropic
statoliths (specialised amyloplasts that synthesize and store starch involved in the perception of gravity). they are denser than cytoplasm so sink due to gravity to the bottom of the cell
107
Explain how plant roots grow in response to gravity.
Auxin accumulates in cells that are on the…
lower side of the root
inhibits cell elongation
This causes the upper side of the root to grow faster than the lower side, causing the root tip to bend downwards.
108
eg of phototopism
shoot grows upwards towards the light source for photosynthesis to take place
109
what does most research into tropisms use
seedlings that then germinate
changes happen quicker and more obvious
monocotyledinous rather than di
110
phototropisms are the result of the movement of ........ across the ..... or .... if it is exposed to light that is ...... on one side than the other
AUXINS
shoot or root
stronger
111
Explain how plant shoots grow towards a source of light.
Auxin accumulates in cells that are...
In shoot tips, auxin…
1. not facing the light
2. stimulates cell elongation
This causes the side not facing the light to grow faster than the side facing the light, causing the shoot tip to bend towards the light.
112
will plants grow faster and taller or slower and not as tall in even low light than in all round light
taller and faster
113
what is etiolation
when the plant is trying to find the light and so these flowering plants have long, weak stems, longer internodes, smaller leaves, pale yellow colour (chlorosis due to lack of chlorophyll)
no cellulose, lignin, suberin
happens when in partial or complete absence of light
114
if plants are exposed to light which is brighter on one side than the other or to unilateral light that only shines from one side then the shoots/roots will grow
shoots grow towards the light
roots if exposed grow away
115
roots and shoots which is +/- phototrophic
roots are negatively phototrophic
shoots are positively phototrophic
116
what is the survival benefit of phototropism for shoots
as much all round light as possible allowing the maximum amount of photosynthesis to take place
117
what is the survival benefit of phototropism for roots
if the roots should emerge from the soil as they so after particularly heavy rain they will rapidly turn back into the soil
118
what is a clinostat and what can it be used to investigate
a device which uses rotation to negate the effects of gravitational pull on plant growth
investigate geotropism
119
what is a coleoptile
it is the protective sheath covering the emerging shoot in monocots (dont divide but increase in size as accumulate water)
120
light causes auxins to move laterally across the shoot so there is a greater conc on which side
the unilluminated side
121
how does the movement of auxins affect the cell elongation
the high conc of auxins on the unilluminated side stimulate cell elongation and growth on the dark side
resulting in observed growth towards the light
122
once the shoot is growing towards the directly light what happens
the unilateral stimulus is removed/the transport of auxin stops and then the shoot continues to grow directly towards the light
123
what happens when seeds are germinated in the dark
the plant grows more rapidly/the first seedlings dont have to compete for light, gibberellins are responsible for the extreme elongation of the internodes so the plant can grow quickly towards the light
124
how can geotropism be investigated in a lab
by using seedlings and placing them on their side in dark or light conditions
125
are shoots +/- geotropic
negatively geotropic (grow away from gravitational pull)
126
are roots +/- geotropic
positively geotropic as they grow towards the gravitational pull this ensures that the roots grow down into the soil and the shoots grow up to the light
127
geotropisms ar also known as
gravitropisms
128
what is a climacteric fruit
fruits that continue to ripen after picking eg bananas, tomatoes, mangoes, avocados
129
what is a non climacteric fruit
fruits that do not ripen much after picking eg oranges strawbs watermelon
130
what is the ripening of climacteric fruits linked to
a peak in ethene production triggering a series of chem reactions eg big increase in resp rate
131
ethene from one ripe ....... fruit can ..... the ...... of unripe fruit
ethene from one ripe CLIMACTERIC fruit can STIMULATE the RIPENING of unripe fruit
132
do nonclimacteric fruits produce large amounts of ethene
no
133
when unripe fruit is ready for sale they can be exposed to ethene, why is ethene used in commercial fruit production
transporting unripe fruit which is hard ensures less damage
ethene exposure is controlled so each batch of fruit ripens at the same rate and are all able to be put on the shelves when needed
prevents lots of food waste during transport and increases the time available for them to be sold
134
is auxin is applied to cut shoots it stimulates the production of
roots
135
if a plant cutting is dipped in ..... it increases the likelihood of roots forming and a new plant being successful
hormone rooting powder
136
plant hormones are essential in micorpropagation because they control the production of the ............ and then the ......... into tiny new plants
control the production of the mass of new cells and then the differentiation of the clones into tiny new plants
137
how do weeds interfere with crop plants
they compete for light, space, water and minerals
138
many of the worlds staple foods are ..... whereas most weeds are
staple: narrow-leaved monocot
weeds: broad-leaved dicot
139
what do farmers use to kill weeds
synthetic auxins
140
why are synthetic auxins good
simple, cheap to produce, low toxicity to animals, selective
141
how do synthetic auxins effective
applied as weedkiller, absorbed by the weeds and affect their metabolism, growth rate increases and becomes unsustainable so they die, the crops are not affected and so continue to grow normally freed from comp
142
other uses of plant hormones: auxins can be used in the production of ........
seedless fruit
143
other uses of plant hormones: ethene is used to promote .......... in plants such as cotton, walnuts and cherries
fruit dropping
144
other uses of plant hormones: cytokinins are used to prevent ......... of ripened fruit and lettuce
and in micropropagation to control ......
ageing of ripened fruit and lettuce
control tissue development
145
other uses of plant hormones: gibberellins to delay ..........
improve the .... and.... of fruits
in ....... to speed up the .... process
delay ripening and ageing in fruit
improve size and shape of fruit
beer brewing to speed up the malting process
146
What responses are seen in trees in temperate regions to avoid water stress in winter when soil may be frozen? (2)
leaf abscission/drop/fall
dormancy
147
What is the term used to describe the sensitivity of plants to the balance of hours of daylight and dark over the course of a day?
Photoperiodism (plants respond to the lack of light)
148
What term is used for the separation of part of a plant such as a leaf, fruit or flower causing it to fall?
abscission
149
What is the function of the production of solutes in winter to lower the melting point of plant cell cytoplasm?
to prevent cells from freezing
150
How do stomata help prevent overheating in plants?
they open to increase the rate of transpiration which increases the circulation which cools the plant by evaporation
151
What type of plant defence can involve spikes, thorns, hairs or tough tissues?
physical defences
152
Which type of plant defence chemicals have a bitter taste, are toxic to insects and are present in tea and red wine?
tannins
153
Which group of plant defence chemicals include caffeine, nicotine and cocaine?
alkaloids
154
Which group of plant defence chemicals can affect the behaviour of social insects?
plant pherimones
155
Which two environmental stimuli typically bring about tropic responses in plants?
gravity and light
156
What is the term for the promotion of main shoot growth in plants caused by suppression of lateral shoot growth?
What is the term for when the tip of a plant’s stem is dominant over its lateral branches?
apical dominance
157
Which group of plant hormones have a role in cell elongation, apical dominance and tropisms?
auxins
158
Which plant hormone has a role in stem elongation and mobilising food reserves in seedlings?
gibberelines
159
Which plant hormone causes fruit ripening?
ethene
160
Which plant hormone is involved in keeping seeds and buds dormant?
abscisic acid (ABA)
161
Give three commercial uses of plant hormones
control of fruit ripening
rooting powders
weed killers
162
Give three examples of physical barriers which help plants prevent the entry of pathogens.
Waxy cuticles
Closing stomata
Thick cellulose cell walls
163
Name two methods used by plants to prevent the spread of infection
To prevent the spread of infection, plants produce callose or detach the infected part in a process called abscission.
164
Describe how auxin can be used to grow more plants.
First, a small piece is cut from a plant’s stem.
This small piece is called a cutting
Then, it is dipped into a rooting powder that contains auxin, before being planted in soil.
165
Where is callose deposited to help prevent the spread of a pathogen in a plant?
Callose is deposited between the cell surface membrane and the cell wall.
166
Describe how auxin can be used as a weedkiller.
Auxin is applied at higher concentrations to the weed.
this causes uncontrolled shoot growth, causing the weed to die
167
Plants produce specific chemicals to act as a defence against pathogens.
How can these chemicals protect plants?
By repelling pathogens
By killing pathogens
By preventing the growth of pathogens
168
To defend themselves against herbivory, some plants fold their leaves.
They do this in response to…
touch
169
suggest one biotic and abiotic stress that might particularly affect flowers growing on motorway central regions compared to growing in open countryside
biotic:
mowing
fewer bees/pollinators/insects
lack of grazers
impoverished soil community
abiotic:
limited space
soil chemistry
wind from vehicle (slipstream)
mud/dust covering leaves
named pollution from vehicles/exhaust gases eg CO, NOx, SOx
170
which plant hormones are/thought to be involved in the control of leaf drop
auxin
ethene
possibly gibberellin
171
which plant hormone would fix this problem: bananas picked green and shipped in a container are not ripe when the ship arrives
ethene
172
which plant hormone would fix this problem: pot plants grown for sale at christmas will not be bought if their leaves drop off
auxin
173
which plant hormone would fix this problem: barley grains delivered to a brewery do not contain much maltose for the yeast
gibberellins
174
which plant hormone would fix this problem: in plant tissue culture, calluses on plain agar will e too slow in developing shoot buds
cytokinins
175
which of these are true relating to phototropism:
the factor causing phototropism moves away from the tip
the factor causing phototropism is not an electrical impulse.
the factor causing phototropism moves away from the light
all are true
176
state the name of the plant hormone expected to affect root growth
auxins
177
in the investigation (effect of plant hormone conc on root growth) the students controlled light, temp and mineral conc. state one other factor that needs controlling
soil/water pH
species of plant
age of plant
size of plant
soil type
water availability
178
what can be concluded about how a statocyte controls root growth (2)
statoctye- specialised cell controlling root growth, contains amyloplasts that fall
amyloplasts are dense/heavy
the root grows to the side of the amyloplasts
binding of amyloplasts with ER releases Ca2+ which is a growth factor (all shown in figure)
179
