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A level Biology > Plant responses > Flashcards

Plant responses Flashcards

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1
Q

what is herbivory ?

A

plant being eaten by animals / insects

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2
Q

state ways plants respond to herbivory

A
  • release toxic chemicals like tannins and alkaloids
  • release pheromones
  • fold up (knock off insects / scares off animal)
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3
Q

what are alkaloids and how do they help against herbivory ?

A
  • chemicals w/ bitter tastes / noxious smells / poisons

e. g. tobacco produces nicotine which is poisonous to insects

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4
Q

what are tannins and how do they help against herbivory ?

A
  • bitter tasting chemicals
  • bind to proteins in gut, making hard to digest plant
    (deterrence)
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5
Q

how do pheromones help against herbivory ?

A
  • alarm pheromones causes nearby plants to produce chemicals like tannin
  • may attract other organisms which will kill herbivore (attract wasps to kill caterpillars)
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6
Q

describe how carrots respond to cold conditions

A
  • produce antifreeze proteins
  • proteins bind to ice crystals and lowers the freezing point
  • stops more ice crystals from forming
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7
Q

state what a tropism is

A

response of a plant to a directional stimulus

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8
Q

what are the meanings of positive / negative tropisms ?

A

positive - growth towards stimulus

negative - growth away from stimulus

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9
Q

state the 5 different tropisms

A

phototropism / geotropism / hydrotropism / thermotropism / thigmotropism

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10
Q

what is phototropism ?

A

plant growth in response to light
(shoots +ve as grown towards light)
(roots -ve as grow away from light)

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11
Q

what is geotropism ?

A

plant growth in response to gravity
(shoots -ve as grow away from gravity)
(roots +ve as grow towards gravity)

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12
Q

what is hydrotropism ?

A

plant growth in response to water

roots +ve as grow towards water

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13
Q

what is thermotropism ?

A

plant growth in response to temperature

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14
Q

what is thigmotropism ?

A

plant growth in response to contact with an object

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15
Q

what are the two growth hormones ?

A

gibberellin and auxins

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16
Q

what does gibberellin do ?

A

stimulates seed germination, stem elongation, side shoot formation and flowering

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17
Q

what do auxins do ?

A

stimulate growth of shoots and roots by cell elongation

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18
Q

state the name of the main auxin

A

Indoleacetic acid (IAA)

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19
Q

how does IAA affect shoots for phototropism ?

A
  • moves to more shaded side
  • cells elongate on this side
  • shoot bends towards light
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20
Q

how does IAA affect roots for phototropism ?

A
  • moves to more shaded side
  • growth is inhibited on this side
  • root bends away from light
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21
Q

how does IAA affect shoots for geotropism ?

A
  • moves to underside of shoot
  • cells elongate
  • shoot grows upwards
22
Q

how does IAA affect roots for geotropism ?

A
  • moves to underside of root
  • cell growth inhibited
  • roots grows downwards
23
Q

outline the process of testing phototropism

A
  1. 9 wheat shoots planted in separate pots
  2. cover tip of 3 w/ foil cap, wrap base of 3 with foil and leave 3 exposed
  3. set up in front of light source
  4. after two days, record amount of growth (mm) and direction of growth
24
Q

state the variables to be controlled for phototropism test

A

length of shoots, soil type, distance from light source, light intensity, temp, moisture …

25
Q

outline the process of testing geotropism

A
  1. three petri dishes with 10 cress seeds
  2. tape lid and wrap foil around each
  3. chose location with warm and constant conditions
  4. leave dishes, one at 90 degrees, 45 and flat for 4 days
  5. measure amount of growth of shoots and roots and angle of growth
26
Q

what is apical dominance ?

A

growth of apical bud stimulated by auxins - growth of side shoots from lateral buds inhibited

27
Q

what is the apical bud and lateral buds ?

A

apical bud - shoot tip at top of flowering plant

lateral buds - bud where side shoots grow from

28
Q

what is the point in apical dominance ?

A
  • energy used to grow tall faster to reach sun light

- also prevents side shoots from competing with shoot tip for light

29
Q

what happens, in terms of apical dominance, if the apical buds is removed ?

A

side shoots grow by cell division and cell elongation

30
Q

why do tall plants show more side shoots at bottom of plant ?

A
  • auxins become less conc as apical bud moves further away

- bottom parts have lower auxin conc, so side shoots grow

31
Q

how do you investigate apical dominance ?

A
  • one set of plants w/ tip cut off but w/ auxin paste
  • one set w/ tip cut off
  • one set left as they are
  • leave for few days and then count number of side shoots
32
Q

how do gibberellins stimulate seed germination ?

A
  • Gib stimulate production of protease enzymes
  • protease hydrolyses storage proteins to aas
  • Gib stimulates prod. of amylase
  • amylase hydrolyses starch to maltose
33
Q

what is the molecule that inhibits gibberellins ?

A

abscisic acid

34
Q

why would seed germination be inhibited ?

A
  • so seed develops fully first

- dispersed away from parent plant

35
Q

what is seed dormancy ?

A

term for inhibition of seed germination

36
Q

how do you investigate role of gibberellins in stem elongation ?

A
  • several plants left as control
  • several plants watered w/ dilute Gib solution
  • those w/ Gib sol. will have grown taller
37
Q

what is the term for gibberellins and auxins working together and give an example

A

synergistic

work together to make plant tall

38
Q

what is the term for gibberellins and auxins opposing each other and give an example

A

antagonistic

Gib stimulate side shoot growth, auxins inhibit side shoot growth

39
Q

state the term for a plant that loses all its leave in winter

A

deciduous plant

40
Q

what is the term for leaf loss ?

A

abscission

41
Q

what is the point in abscission ?

A

helps plants conserve water (hard to absorb frozen soil / little sunlight)

42
Q

what is abscission triggered by ?

A

shortening day length in autumn

43
Q

outline how abscission is carried out

A
  • ethene produced by old leaves and builds up
  • abscission layer forms and bottom of leaf stalk
  • ethene stimulates abscission layer to expand
  • cell walls break, leaf falls off
44
Q

what inhibits abscission ?

A

auxins (produced in young leaves, less so in old leaves)

45
Q

state the state of guard cells for open stomata

A

turgid

46
Q

state the state of guard cells for closed stomata

A

flaccid

47
Q

what controls opening/closing of stomata ?

A

abscisic acid (ABA)

48
Q

outline process of how stomata close

A
  • ABA binds to guard cell membrane receptors
  • Ca ions move from vacuole to cytosol (cytoplasm)
  • increase in Ca causes other ion channels to open
  • K ions leave guard cells
  • water pot. increases
  • water leaves, cell becomes flaccid
49
Q

state how plant hormone ethene is used commercially

A
  • ethene stimulates enzymes that break down cells walls and chlorophyll, making fruit softer and riper
  • fruit transported before ripe, then exposed to ethene
50
Q

state how plant hormone auxin is used commercially as weed killers

A
  • make weeds produce long stems w/out leaves

- weed grows too fast and dies

51
Q

state how plant hormone auxin is used commercially as rooting hormones

A

make cuttings grow roots

A level Biology (26 decks)

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