Plant responses

Question 1

what is herbivory ?

Answer 1

plant being eaten by animals / insects

Question 2

state ways plants respond to herbivory

Answer 2

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

Question 3

what are alkaloids and how do they help against herbivory ?

Answer 3

• chemicals w/ bitter tastes / noxious smells / poisons

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

Question 4

what are tannins and how do they help against herbivory ?

Answer 4

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

Question 5

how do pheromones help against herbivory ?

Answer 5

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

Question 6

describe how carrots respond to cold conditions

Answer 6

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

Question 7

state what a tropism is

Answer 7

response of a plant to a directional stimulus

Question 8

what are the meanings of positive / negative tropisms ?

Answer 8

positive - growth towards stimulus

negative - growth away from stimulus

Question 9

state the 5 different tropisms

Answer 9

phototropism / geotropism / hydrotropism / thermotropism / thigmotropism

Question 10

what is phototropism ?

Answer 10

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

Question 11

what is geotropism ?

Answer 11

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

Question 12

what is hydrotropism ?

Answer 12

plant growth in response to water

roots +ve as grow towards water

Question 13

what is thermotropism ?

Answer 13

plant growth in response to temperature

Question 14

what is thigmotropism ?

Answer 14

plant growth in response to contact with an object

Question 15

what are the two growth hormones ?

Answer 15

gibberellin and auxins

Question 16

what does gibberellin do ?

Answer 16

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

Question 17

what do auxins do ?

Answer 17

stimulate growth of shoots and roots by cell elongation

Question 18

state the name of the main auxin

Answer 18

Indoleacetic acid (IAA)

Question 19

how does IAA affect shoots for phototropism ?

Answer 19

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

Question 20

how does IAA affect roots for phototropism ?

Answer 20

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

Question 21

how does IAA affect shoots for geotropism ?

Answer 21

• moves to underside of shoot
• cells elongate
• shoot grows upwards

Question 22

how does IAA affect roots for geotropism ?

Answer 22

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

Question 23

outline the process of testing phototropism

Answer 23

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

Question 24

state the variables to be controlled for phototropism test

Answer 24

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

Question 25

outline the process of testing geotropism

Answer 25

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

Question 26

what is apical dominance ?

Answer 26

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

Question 27

what is the apical bud and lateral buds ?

Answer 27

apical bud - shoot tip at top of flowering plant | lateral buds - bud where side shoots grow from

Question 28

what is the point in apical dominance ?

Answer 28

- energy used to grow tall faster to reach sun light | - also prevents side shoots from competing with shoot tip for light

Question 29

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

Answer 29

side shoots grow by cell division and cell elongation

Question 30

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

Answer 30

- auxins become less conc as apical bud moves further away | - bottom parts have lower auxin conc, so side shoots grow

Question 31

how do you investigate apical dominance ?

Answer 31

- 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

Question 32

how do gibberellins stimulate seed germination ?

Answer 32

- Gib stimulate production of protease enzymes - protease hydrolyses storage proteins to aas - Gib stimulates prod. of amylase - amylase hydrolyses starch to maltose

Question 33

what is the molecule that inhibits gibberellins ?

Answer 33

abscisic acid

Question 34

why would seed germination be inhibited ?

Answer 34

- so seed develops fully first | - dispersed away from parent plant

Question 35

what is seed dormancy ?

Answer 35

term for inhibition of seed germination

Question 36

how do you investigate role of gibberellins in stem elongation ?

Answer 36

- several plants left as control - several plants watered w/ dilute Gib solution - those w/ Gib sol. will have grown taller

Question 37

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

Answer 37

synergistic | work together to make plant tall

Question 38

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

Answer 38

antagonistic | Gib stimulate side shoot growth, auxins inhibit side shoot growth

Question 39

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

Answer 39

deciduous plant

Question 40

what is the term for leaf loss ?

Answer 40

abscission

Question 41

what is the point in abscission ?

Answer 41

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

Question 42

what is abscission triggered by ?

Answer 42

shortening day length in autumn

Question 43

outline how abscission is carried out

Answer 43

- 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

Question 44

what inhibits abscission ?

Answer 44

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

Question 45

state the state of guard cells for open stomata

Answer 45

turgid

Question 46

state the state of guard cells for closed stomata

Answer 46

flaccid

Question 47

what controls opening/closing of stomata ?

Answer 47

abscisic acid (ABA)

Question 48

outline process of how stomata close

Answer 48

- 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

Question 49

state how plant hormone ethene is used commercially

Answer 49

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

Question 50

state how plant hormone auxin is used commercially as weed killers

Answer 50

- make weeds produce long stems w/out leaves | - weed grows too fast and dies

Question 51

state how plant hormone auxin is used commercially as rooting hormones

Answer 51

make cuttings grow roots