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alevel biology ocr > chapter 16 plant responses > Flashcards

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

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2
Q

how can chemicals/hormones be transported throughout a plant

A

through the transport vessels and cell to cell

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3
Q

What are plant hormones?

A

Plant hormones are signalling molecules that enable plants to respond to changes in the environment.

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4
Q

plant hormones are produced in one region of a plant and have an effect in….

A

another part of the plant

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5
Q

what can be added to a plant to inhibit the production of gibberellins

A

biosynthesis inibitors

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6
Q

Plant hormones enable plants to…

A

access resources such as light, minerals, and water.
avoid abiotic stress.
avoid being eaten by predators.

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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

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8
Q

ABA is also known as

A

abscisic acid

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9
Q

what does aba do: maintains….. of …. and …

A

maintains dormancy of seeds and buds

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10
Q

what does aba do: stimulates …. ….. responses and eg

A

stimulates cold protective responses eg antifreeze production

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11
Q

what does aba do: stimulates ……. closing

A

stimulates stomatal closing

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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

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13
Q

what does ethene do: causes…

A

causes fruit ripening

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14
Q

what does ethene do: promotes …… in ….. trees

A

promotes abscission in deciduous tress

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15
Q

what is abscission

A

leaf fall

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16
Q

what do auxins do: control …… …..

A

control cell elonglation

by the conc of auxin

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17
Q

what do auxins do: prevent …

A

prevent abscission

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18
Q

what do auxins do: maintain …… dominance

A

maintain apical dominance

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19
Q

what do auxins do: involved in ……

A

involved in tropisms

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20
Q

what do auxins do: stimulate the release of

A

ethene

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21
Q

what do auxins do: involved in fruit

A

ripening

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22
Q

what do gibberellins do: cause stem….

A

elongation

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23
Q

what do gibberellins do: trigger the mobilisation of food stores in ……

A

a seed at germination

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24
Q

what do gibberellins do: stimulate …… …… growth in fertilisation

A

stimulate pollen tube growth in fertilisation

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25
Q

Which plant hormone has a role in stem elongation, stomatal closure, and seed germination?

A

gibberellins

stomatal closure (stimulates it)

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26
Q

the growth and form of a plant are the result of the interaction of many different ……. and …….. factors

A

hormonal and environmental factoes

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27
Q

why are scientists still unsure about the details of many plant responses

A

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

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28
Q

what is the first plant hormone involved in seed germination and how is it activated

A

when the seed absorbs water the embryo is activated and begins to produce GIBBERELLINS

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29
Q

in seed germination what do gibberellins stimulate

A

the production of enzymes that break down the food stores in the seed
(cotyledons in dicot seeds and endosperm in monocot seeds)

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30
Q

in seed germination what happens to the food stores that are broken down

A

the embryo plant uses them to produce atp (to make things) for growth and then break out through the seed coat

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31
Q

evidence suggests that in seed germination gibberellins switch on genes which code for ……

A

amylases and proteases the digestive enzymes required for germination (amylase, maltase)

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32
Q

evidence suggests that in seed germination ABA acts as an ……. to ……. and therefore seed germination is determined by

A

aba acts as an antagonist to gibberellins and that it is the relative levels of both hormones which determine when a seeds will germinate

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33
Q

where is the food store in dicots and monocots

A

dicots: in the cotyledons (seed leaves)
moncots: in the endosperm

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34
Q

eg of an auxin

A

IAA (indoleacetic acid) growth stimulants produced in plants, small amount = big effect

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35
Q

where are auxins synthesised

A

in the tip of roots and shoots and in the meristems

in the zone of cell division

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36
Q

what type of cells are in the meristems

A

undifferentiated (meristematic cells)

they are similar to stem cells in humans

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37
Q

what are the 3 types of meristematic tissues/meristems

A

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)

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38
Q

can auxins move around the plant?

A

they can move down the stem and up the root in transport tissue and from cell to cell

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39
Q

the effect of auxin depends on ………. and ……..

A

its conc and interactions it has with other hormones

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40
Q

evidence suggest auxins affect the ….. of the cell wall- presence =

A

plasticity of the cell wall- presence = cw stretches more easily

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41
Q

how do auxins play a role in the cell wall of a plant cell becoming rigid

A

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

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42
Q

auxins stimulate the growth of ….

A

the main apical shoot

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43
Q

how do auxins stimulate the growth of the main apical shoot (what is the process)

A

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.

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44
Q

high concentrations of auxins supress the growth of ………. which results in

A

lateral shoots resulting in apical dominance

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45
Q

further down the stem the auxin con is ……. so the lateral shoots grow ……

A

auxin conc is lower so lateral shoots grow more strongly

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46
Q

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

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

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47
Q

low conc of auxin promotes …..

A

root growth (and lateral shoot growth)

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48
Q

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?

A

grow

the translocation of auxin to the roots is removed so the growth of roots is reduced

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49
Q

what happens to root growth if the apical shoot is removed

A

the amount of auxin reaching the roots is greatly reduced and so root growth slows and stops

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50
Q

high auxin concentrations also inhibit … elongation but instead enhances…..

A

root
branching root formation

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51
Q

gibberellins affect the length of the … - the regions between the leaves on a stem

A

internodes

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52
Q

plants that have short stems produce many or few gibberellins

A

few or none

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53
Q

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

A

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

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54
Q

what is meant by synergism

A

when plant hormones work together/complementary to produce a greater response then they wouldve individually

magnifying the response

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55
Q

what is meant by antagonism

A

if the substances have opposite effects eg one promotes one inhibits growth

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56
Q

what is thigmotropism

A

spiraling around something eg sweetpeas around a cane wmt they dont have a need for lignin

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57
Q

what is helicotropism

A

diurnal motion of seasonal motion of plant parts in response to the direction of the sun

eg turning of sunflower

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58
Q

why do seasonal changes have a big affect on the amount of photosynthesis possible

A

because light and temperature change with the seasons and they have an affect on photosynthesis

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59
Q

why do deciduous trees lose their leaves and become dormant

A

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

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60
Q

contrast plant and animal hormones on 4 points

A

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.

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61
Q

glucose balance causing leaf loss

A

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

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62
Q

what is photoperiodism and what are the responses plants could take

A

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)

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63
Q

what plant responses are affected by the photoperiod

A

timing of flowering in a plant, when tubers are formed in prep for overwintering, breaking dormancy of leaf buds so they open

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64
Q

what is the light sensitive pigment which exists in the forms Pr and Pfr

A

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

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65
Q

what triggers absiccion and a period of dormancy

A

the lengthening of the dark period

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66
Q

the falling in light levels results in the falling conc of which plant hormone

A

auxin

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67
Q

how do leaves respond to the falling of auxin conc

A

producing ethene

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68
Q

what is the region called at the base of the lead stalk and what is special about it

A

the abscission zone and it is made up of two layers of cells sensitive to ethene

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69
Q

how does ethene affect the cell walls of the cells in the outer layer of the abscission zone/separation layer during abscission

A

ethene initiates gene switching in these cells = production of enzymes which digest and weaken the cells walls

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70
Q

what happens to the vascular bundles in the petioles and fatty material in abscission

A

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

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71
Q

what do cells in the protective layer of the abscission zone make and why

A

suberin and lignin to waterproof and protect the scar when the leaf falls off

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72
Q

how do cells deep in the separation zone respond to hormonal cues during abscission

A

they retain water and swell putting more strain on the outer layer, they burst and make the leaf fall off.

73
Q

how have cells adapted to lower the freezing point of the cell

A

cytoplasm of plant cells and sap in the vacuole contain solutes which lower the freezing point

74
Q

some plants produce ………. which act as antifreeze and what stimulates them to do this

A

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
Q

what changes take place within the plant which make it able to withstand frosty conditions (dna level)

A

genes are suppressed and activated

76
Q

opening stomata allows the plant to …… and water …..

A

allows the plant to cool as water evaporated from the cells in the leaves in transpiration

closing stomata conserves water

77
Q

stomatal control in response to abiotic stresses is largely under control of which hormone and what happens

A

ABA

leaves release ABA under abiotic stress causing stomatal closure

78
Q

how else can ABA cause stomatal closure (hint roots)

A

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
Q

how does aba cause stomatal opening

A

osmosis of water into guard cell as the wp is lowered as k+ go in.

increase in turgor pressure so stomata open

80
Q

in experiments seeds can be grown hydroponically in serial dilutions of different hormones what does this mean

A

in nutrient solution rather than soil

81
Q

when investigating plant hormones why is it important to make serial dilutions

A

to observe the effects of different conc of hormones as they can have differenr effects on growth at different concs

82
Q

how can standard deviation be used when investigating plant hormones

A

the experiments usually involve large numbers of plants, the spread of data from each experimental group should be measured using standard deviation

83
Q

what is herbivory

A

the process by which herbivores eat plants

84
Q

what are some physical defences that plants have in response to herbivory

A

thorns, spiny leaves, fibrous and inedible tissue, stings, hairy leaves, spikes

protect themselves and discourage herbivores from eating them

85
Q

what are the 4 chemical defences that plants have in response to herbivory

A

tannins, alkaloids, terpenoids, pheromones

86
Q

what are tannins and how do they work

A

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
Q

tannins can be found highly in

A

tea and red wine

88
Q

eg of alkaloids

A

caffeine, nicotine, morphine, cocaine

89
Q

how do alkaloids work

A

very bitter tasting, large group of nitrogenous compounds, many act as drugs affecting metabolism of the herbivore and sometimes poisoning them

90
Q

how does caffeine work to protect the plant

A

toxic to fungi and insects, spreads through the soil and prevents germination of other seeds of plants - protects against herbivores and plant rivals

91
Q

how does nicotine work to protect the plant

A

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
Q

What type of chemical makes it harder for herbivores to eat plants?

A

pheromones

93
Q

eg of terpenoids

A

pyrethin, citronella

94
Q

terpenpoids often form ….. but also act as …… to insects and fungi that might attack the plant

A

essential oils, toxins

they are metabolites involved in physiological processes

95
Q

how does pyrethin work

A

produced by chrysanthemums acts as an insect neurotoxin interferring with the nervous system

96
Q

what does citronella do

A

repels insects, it is produced by lemon grass

97
Q

what is a pheromone

A

chemical made by an organism which affects the social behaviour of other members of the same species

98
Q

how do plants use pheromones in response to herbivory eg maple tree

A

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
Q

plants also produce VOCs which work like pheromones they stand for

A

volatile organic compounds

100
Q

how do VOCs work in response to herbivory

A

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
Q

how does mimosa pudica respond to herbivory

A

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
Q

what is pulvinus

A

specialised organ that enable leaf movement

103
Q

what is a tropism

A

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
Q

what is geotropism

A

the response to gravity

105
Q

what is photostopism

A

the response to light which comes from one direction only

106
Q

eg of geotropism

A

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
Q

Explain how plant roots grow in response to gravity.

Auxin accumulates in cells that are on the…

A

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
Q

eg of phototopism

A

shoot grows upwards towards the light source for photosynthesis to take place

109
Q

what does most research into tropisms use

A

seedlings that then germinate
changes happen quicker and more obvious
monocotyledinous rather than di

110
Q

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

A

AUXINS
shoot or root
stronger

111
Q

Explain how plant shoots grow towards a source of light.

Auxin accumulates in cells that are…
In shoot tips, auxin…

A
  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
Q

will plants grow faster and taller or slower and not as tall in even low light than in all round light

A

taller and faster

113
Q

what is etiolation

A

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
Q

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

A

shoots grow towards the light
roots if exposed grow away

115
Q

roots and shoots which is +/- phototrophic

A

roots are negatively phototrophic
shoots are positively phototrophic

116
Q

what is the survival benefit of phototropism for shoots

A

as much all round light as possible allowing the maximum amount of photosynthesis to take place

117
Q

what is the survival benefit of phototropism for roots

A

if the roots should emerge from the soil as they so after particularly heavy rain they will rapidly turn back into the soil

118
Q

what is a clinostat and what can it be used to investigate

A

a device which uses rotation to negate the effects of gravitational pull on plant growth

investigate geotropism

119
Q

what is a coleoptile

A

it is the protective sheath covering the emerging shoot in monocots (dont divide but increase in size as accumulate water)

120
Q

light causes auxins to move laterally across the shoot so there is a greater conc on which side

A

the unilluminated side

121
Q

how does the movement of auxins affect the cell elongation

A

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
Q

once the shoot is growing towards the directly light what happens

A

the unilateral stimulus is removed/the transport of auxin stops and then the shoot continues to grow directly towards the light

123
Q

what happens when seeds are germinated in the dark

A

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
Q

how can geotropism be investigated in a lab

A

by using seedlings and placing them on their side in dark or light conditions

125
Q

are shoots +/- geotropic

A

negatively geotropic (grow away from gravitational pull)

126
Q

are roots +/- geotropic

A

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
Q

geotropisms ar also known as

A

gravitropisms

128
Q

what is a climacteric fruit

A

fruits that continue to ripen after picking eg bananas, tomatoes, mangoes, avocados

129
Q

what is a non climacteric fruit

A

fruits that do not ripen much after picking eg oranges strawbs watermelon

130
Q

what is the ripening of climacteric fruits linked to

A

a peak in ethene production triggering a series of chem reactions eg big increase in resp rate

131
Q

ethene from one ripe ……. fruit can ….. the …… of unripe fruit

A

ethene from one ripe CLIMACTERIC fruit can STIMULATE the RIPENING of unripe fruit

132
Q

do nonclimacteric fruits produce large amounts of ethene

A

no

133
Q

when unripe fruit is ready for sale they can be exposed to ethene, why is ethene used in commercial fruit production

A

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
Q

is auxin is applied to cut shoots it stimulates the production of

A

roots

135
Q

if a plant cutting is dipped in ….. it increases the likelihood of roots forming and a new plant being successful

A

hormone rooting powder

136
Q

plant hormones are essential in micorpropagation because they control the production of the ………… and then the ……… into tiny new plants

A

control the production of the mass of new cells and then the differentiation of the clones into tiny new plants

137
Q

how do weeds interfere with crop plants

A

they compete for light, space, water and minerals

138
Q

many of the worlds staple foods are ….. whereas most weeds are

A

staple: narrow-leaved monocot
weeds: broad-leaved dicot

139
Q

what do farmers use to kill weeds

A

synthetic auxins

140
Q

why are synthetic auxins good

A

simple, cheap to produce, low toxicity to animals, selective

141
Q

how do synthetic auxins effective

A

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
Q

other uses of plant hormones: auxins can be used in the production of ……..

A

seedless fruit

143
Q

other uses of plant hormones: ethene is used to promote ………. in plants such as cotton, walnuts and cherries

A

fruit dropping

144
Q

other uses of plant hormones: cytokinins are used to prevent ……… of ripened fruit and lettuce
and in micropropagation to control ……

A

ageing of ripened fruit and lettuce
control tissue development

145
Q

other uses of plant hormones: gibberellins to delay ……….
improve the …. and…. of fruits
in ……. to speed up the …. process

A

delay ripening and ageing in fruit
improve size and shape of fruit
beer brewing to speed up the malting process

146
Q

What responses are seen in trees in temperate regions to avoid water stress in winter when soil may be frozen? (2)

A

leaf abscission/drop/fall
dormancy

147
Q

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?

A

Photoperiodism (plants respond to the lack of light)

148
Q

What term is used for the separation of part of a plant such as a leaf, fruit or flower causing it to fall?

A

abscission

149
Q

What is the function of the production of solutes in winter to lower the melting point of plant cell cytoplasm?

A

to prevent cells from freezing

150
Q

How do stomata help prevent overheating in plants?

A

they open to increase the rate of transpiration which increases the circulation which cools the plant by evaporation

151
Q

What type of plant defence can involve spikes, thorns, hairs or tough tissues?

A

physical defences

152
Q

Which type of plant defence chemicals have a bitter taste, are toxic to insects and are present in tea and red wine?

A

tannins

153
Q

Which group of plant defence chemicals include caffeine, nicotine and cocaine?

A

alkaloids

154
Q

Which group of plant defence chemicals can affect the behaviour of social insects?

A

plant pherimones

155
Q

Which two environmental stimuli typically bring about tropic responses in plants?

A

gravity and light

156
Q

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?

A

apical dominance

157
Q

Which group of plant hormones have a role in cell elongation, apical dominance and tropisms?

A

auxins

158
Q

Which plant hormone has a role in stem elongation and mobilising food reserves in seedlings?

A

gibberelines

159
Q

Which plant hormone causes fruit ripening?

A

ethene

160
Q

Which plant hormone is involved in keeping seeds and buds dormant?

A

abscisic acid (ABA)

161
Q

Give three commercial uses of plant hormones

A

control of fruit ripening
rooting powders
weed killers

162
Q

Give three examples of physical barriers which help plants prevent the entry of pathogens.

A

Waxy cuticles
Closing stomata
Thick cellulose cell walls

163
Q

Name two methods used by plants to prevent the spread of infection

A

To prevent the spread of infection, plants produce callose or detach the infected part in a process called abscission.

164
Q

Describe how auxin can be used to grow more plants.

A

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
Q

Where is callose deposited to help prevent the spread of a pathogen in a plant?

A

Callose is deposited between the cell surface membrane and the cell wall.

166
Q

Describe how auxin can be used as a weedkiller.

A

Auxin is applied at higher concentrations to the weed.

this causes uncontrolled shoot growth, causing the weed to die

167
Q

Plants produce specific chemicals to act as a defence against pathogens.

How can these chemicals protect plants?

A

By repelling pathogens
By killing pathogens
By preventing the growth of pathogens

168
Q

To defend themselves against herbivory, some plants fold their leaves.

They do this in response to…

A

touch

169
Q

suggest one biotic and abiotic stress that might particularly affect flowers growing on motorway central regions compared to growing in open countryside

A

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
Q

which plant hormones are/thought to be involved in the control of leaf drop

A

auxin
ethene

possibly gibberellin

171
Q

which plant hormone would fix this problem: bananas picked green and shipped in a container are not ripe when the ship arrives

A

ethene

172
Q

which plant hormone would fix this problem: pot plants grown for sale at christmas will not be bought if their leaves drop off

A

auxin

173
Q

which plant hormone would fix this problem: barley grains delivered to a brewery do not contain much maltose for the yeast

A

gibberellins

174
Q

which plant hormone would fix this problem: in plant tissue culture, calluses on plain agar will e too slow in developing shoot buds

A

cytokinins

175
Q

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

A

all are true

176
Q

state the name of the plant hormone expected to affect root growth

A

auxins

177
Q

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

A

soil/water pH
species of plant
age of plant
size of plant
soil type
water availability

178
Q

what can be concluded about how a statocyte controls root growth (2)

statoctye- specialised cell controlling root growth, contains amyloplasts that fall

A

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
Q
A

alevel biology ocr (29 decks)

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