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Biology Module 5 > 5.5 Plant Resposes > Flashcards

5.5 Plant Resposes Flashcards

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1
Q

What do plants respond to?

A

external stimulus’ that are biotic (living) or abiotic (non living)

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2
Q

Do plants have sense organs?

A

No, instead they’re able to detect changes then produce relevant changes as a response.

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3
Q

Physical defences of plants

A

Cellulose cell wall, waxy cuticle, guard cells, callose

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4
Q

Cellulose cell wall

A

Physical barrier.
Lignin thickening of cell walls - waterproof and indigestible

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5
Q

Waxy cuticle

A

Prevents water from collecting on the surface (pathogens need water)

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6
Q

Guard cells

A

Can close the stomata

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7
Q

Callose

A

Large polysaccharide that is deposited in sieve tubes at the end of the growing season. Blocks the flow so that pathogens can’t spread.

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8
Q

Chemical signals of plants when they’re in danger

A

Tannins, alkaloids, pheromones

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9
Q

Tannins

A

chemical released in leaves that make the leaves taste bad and they’re toxic to microbes so it prevents the entry of pathogens.

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10
Q

Alkaloids

A

Chemical released in leaves that make the leaves taste bitter

Poison and affect the metabolism of insects which ingest them.

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11
Q

Pheromones

A

chemicals released by one plant that tells the nearby plants if there’s danger or limiting resources etc

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12
Q

Directional responses

A

Aka tropism

grows towards or away from that stimulus

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13
Q

Types of tropism

A

Phototropism
Geotropism
Chemotropism
Thigmotropism

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14
Q

Phototropism

A

plant grows towards the light if positively and grows away from light if negatively phototropic

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15
Q

Geotropism

A

roots of the plant grows towards gravity if positively and grows away from gravity if negatively geotropic

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16
Q

Chemotropism

A

plant grows towards the chemicals if positively and grows away from chemicals if negatively chemotropic

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17
Q

Chemotropism example

A

fertilisation in a plant, the embryonic sac of the plant releases chemical which promotes the growth of the pollen towards it

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18
Q

Thigmotropism + example

A

grows towards support e.g. shoots wind around other plants or solid structures to gain support

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19
Q

Another name for non directional responses

A

Nastic responses

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20
Q

Example of nastic response

A

some plants e.g. mimosa pudica have leaves and when you touch them the leaves close = thigmonastic response = caused by local bio electrical signals (not plant hormones)

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21
Q

Do plants have glands

A

No

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22
Q

Neurotoxin

A

a chemical that interferes with the ability of neurones to conduct nerve impulses

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23
Q

Cytokinins effects

A

Promote cell division
Delay leaf senescence
Overcome apical dominance
Promote cell expansion
Promote growth of side shoots

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24
Q

Abscisic acid effects

A

Inhibits seed germination and growth
Causes stomatal closure when the plant is stressed by low water availability

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25
Q

Auxins
e.g. IAA (indole-3-acetic acid) effects

A

Promote cell elongation
Inhibit growth of side-shoots
Inhibit leaf abscission (leaf fall)

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26
Q

Gibberellins effects

A

Promote seed germination and stem elongation
Prevents leaf abscission
Promotoe fruit development

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27
Q

Ethene effects

A

Promotes fruit ripening

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28
Q

Senescence

A

Aging

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29
Q

Apical dominance

A

when the apical bud keeps on growing upwards

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30
Q

What happens to the lateral buds when there’s less auxin

A

They grow

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31
Q

When do apical buds grow?

A

When there’s high to normal auxin levels

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32
Q

How to make the plant grow sideways

A

Apical bud can be cut = auxin from the apical bud prevented lateral buds from growing = when shoot is cut, auxin levels drop and the buds grow.

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33
Q

Growth from lateral buds

A

Grows sideways

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34
Q

Where are the apical buds located

A

At the top of the plant

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35
Q

What do auxins promote

A

Apical dominance = The auxins that are produced at the growing tip at the apex (i.e. the top) of a plant stem cause the stem to grow upwards and also stop lateral (side) buds from growing

36
Q

What does cytokinins do the opposite of?

A

Auxins

37
Q

What does Abscisic acid inhibit

A

Seed germination

38
Q

Where is auxin produced

A

In the apical bud

39
Q

Abscisic acid in terms of growth

A

high auxin keeps abscisic acid levels high. When auxin is removed, abscisic acid levels drop and buds start to grow.

40
Q

Cytokinins in terms of growth

A

high levels of auxin cause cytokinins to move to the shoot apex. When apex is removed, cytokinin spreads evenly around the plant and causes bud growth.

41
Q

Similarity and difference in the way humans and plants secrete hormones

A
  • both work in same way in terms of complementary receptors
  • humans = endocrine glands and
    plants = Cells in different tissues release the hormone = most are peptide hormones which is why they look for a target receptor
42
Q

Difference in way hormone reaches destination in humans and plants

A

Humans = travels through blood via diffusion
Plants = active transport, mass flow, diffusion

43
Q

How did scientists find out that gibberellins promote growth?

A
  • found a dwarf plant and a normal plant and compared the genes and realised one had the genes to make gibberellin and one didn’t
  • The one that didn’t have the genes when given gibberelinic acid it grew taller which shows that gibberelinic acid is the cause for stem elongation
  • The allele was responsible for producing an enzyme that converts GA20 to GA1
  • If you find a way to synthetically add that enzyme you can recreate that condition
44
Q

How do gibberellins cause seed germination

A
  • When a seed absorbs water the embryo releases gibberellin which allows the production of the enzyme amylase (breaks down starch into glucose)
  • Glucose acts as a substrate for respiration and it can be used for protein synthesis = enables growth
45
Q

Germination

A

mobilisation of food reserve and promotion of growth

46
Q

Dormancy

A

stage in which a seed will not germinate.

47
Q

What is needed to produce gibberellins

A

Abiotic factors e.g. water, temperature and light stimulates seeds to produce gibberellins

48
Q

What causes seeds to germinate?

A

Gibberellins will allow seeds to come out of dormancy

49
Q

What causes seeds to be dormant

A

Abscisic acid helps to maintain seed dormancy by inhibiting the production of amylase

50
Q

Do auxins stimulate growth in early germination

A

Yes but high concentration will inhibit germination

51
Q

Auxin experiment control

A

when there’s light the plant is growing towards the light

52
Q

Auxin experiment when the tip was cut

A

No directional growth

53
Q

Auxin experiment When tip was covered by an opaque cap

A

No directional growth

54
Q

Auxin experiment When there’s a transparent cap

A

Growing towards light

55
Q

Auxin experiment When bottom of stem was covered by opaque shield

A

Plant was still growing towards the light = base doesn’t have something that promotes phototropism

56
Q

Auxin experiment When tip was separated by gelatin block (permeable)

A

Phototropism still occurs

57
Q

Auxin experiment When tip is separated by mica block (impermeable)

A

No directional growth = movement was important

58
Q

Conclusion of auxin experiment

A
  • Something produced at the tip is involved in phototropism
  • if you shine light to auxin it always moves towards the shaded side + promotes growth and other side doesn’t grow as much so it bends towards the light
59
Q

How does auxin promote the stretchiness of the cell wall

A
  • Promotes active transport of hydrogen ions from the plasma membrane into the cell wall
  • This lowers the pH of the cell wall where it becomes the optimum pH for the enzyme expansins to work
  • Expansin works by breaking the bonds in cellulose
  • Hydrogen ions disrupt the hydrogen bonds within cellulose so the cell wall becomes less rigid and takes on more water = stretchy + can expand
60
Q

What’s responsible for moving auxins to the shaded side

A

Phototropin 1 and 2 (enzymes)

61
Q

Auxin’s role in geotropism in the roots

A
  • In the roots auxin accumulates on the lower side + inhibits cell elongation so the upper side starts growing more + bends downwards
62
Q

Auxin concentration to promote growth in the roots and shoots

A

Low to promote growth in roots and high in shoots

63
Q

Creating serial dilutions

A
  • start with a stock solution and take 1 cm^3 and add 9 cm^3 of water which makes it 1/10 diluted
  • Then take 1cm^3 this solution and add 9cm^3 water to this which makes it 1/100 diluted and repeat
64
Q

Auxin as rooting powder

A

before planting it encourages root growth

65
Q

IRL uses of auxins

A

As rooting powder
Promotes growth of seedless fruit
Used as a herbicide

66
Q

Auxin as a herbicide

A

causes weeds to grow so fast that they can’t handle it + die

67
Q

IRL use of cytokinins

A
  • Delay aging and prevent the yellowing of lettuce leaves
68
Q

Gibberellins IRL uses

A
    • delay aging if citrus fruits = can be in shops for longer
  • Can work with cytokinins to improve the shape of apples
  • Makes grapes bigger + less compact
  • Can be used in brewing and sugar production
  • sugar production
  • plant breeding
69
Q

Gibberellins in brewing and sugar production

A

it produces amylase that breaks down starch into maltose

Promotes growth of sugar canes

70
Q

Gibberellins in plant breeding

A

speed up process of seed formation + use this knowledge to create giberrelin inhibitors to keep flowers short or delay germination

71
Q

Irl uses of ethene

A
  • promotes ripening of apples, tomatoes and citrus fruit
  • Promotes fruit drop in cotton, cherry and walnut
  • Promotes female sex expression in cucumbers
  • Promote lateral growth in some plants
72
Q

Ethene in promoting female sec expression in cucumbers

A

more likely to be pollinated + decreases the chance of self pollination

73
Q

How do plants respond to drought

A
  • by shutting stomata or dropping their leaves
  • When there’s low water availability for the plant the hormone Abscisic acid is released + promotes Stomatal closure.
74
Q

How do plants respond to freezing

A
  • by producing an antifreeze chemical in their cells that decreases the formation of ice crystals that can destroy plant cells if allowed to form within them
75
Q
A

A

76
Q
A

B

77
Q
A
78
Q

Why does light increase stem and root growth

A

More carbs produced during photosynthesis
Light may trigger growth and germination

79
Q

Phototropism in stems and roots

A

Positive in stems, negative in roots

80
Q

In the investigation, the students controlled light, temperature and mineral concentration.
State one other factor that the students should have controlled in this investigation.

When looking at phototropism

A

Water Availability, soil pH, size of plant

81
Q
A

Amyloplasts are heavy
Binding of amyloplasts with ER releases Ca2+
Ca2+ stimulates growth
Root grows to side of Ca2+ release

82
Q

Auxin and gibberellins given to trees and effects observed:
- shorter roots
- grew taller
- all began to grow within two days of eachother
- had fewer and shorter side branches
- retained their fruit and leaves for longer

Explain each observation

A
83
Q
A
84
Q

Why’s gibberellins classed as a plant hormone

A
  • chemical messenger produced in one part of plant but has effects in another part
  • affects activity of target cells
  • long lasting effects
85
Q
A

1 = light intensity = diff light intensities could lead to variation in phototropism = use same distance from lamp every time

2 = no repeats = can’t calculate mean/do statistical tests = repeat at least twice

Biology Module 5 (8 decks)

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