Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology > Module 5.4 - Plant Responses and Hormones > Flashcards

Module 5.4 - Plant Responses and Hormones Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

How do plants increase their chances of survival, behaviour wise? (3)

A
  • They grown in the direction of light to maximise light absorption for photosynthesis
  • Their roots and shoots grow in accordance to gravity
  • Climbing plants have a sense of touch to help them climb and reach sunlight
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How do plants protect themselves from herbivory? (2)

A
  • Chemical defences
  • Physical defence
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Examples of chemical defences? (3)

A
  • Alkaloids
  • Tannins
  • Pheromones
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Herbivores? (1)

A
  • Animals that eat plants
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Alkaloids? (2)

A
  • Bitter tastes, noxious smells or poisonous characteristics
  • Deter or kill herbivores
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Alkaloids nicotine? (3)

A
  • Tobacco plants
  • Poisonous to many insects
  • Used in response to tissue damage
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Tannins? (3)

A
  • Taste bitter
  • Can bind to proteins in the gut making plant hard to digest
  • Deter animals from eating the plant
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Pheromones? (2)

A
  • Signalling chemicals released into the air in response to herbivore grazing.
  • Cause nearby plants to start making chemical defences
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Example of a pheromone in use? (3)

A
  • When corn plants are being eaten by caterpillars
  • They produce pheromones which attract parasitic wasps
  • These wasps then lay their eggs in the caterpillars which eventually kills them
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Example of a physical defence? (4)

A
  • Plants are able to fold up in response to being touched
  • If a single leaflet of the plant Mimosa pudica is touched, a signal spreads through the whole leaf, causing it to quickly fold up
  • This may knock off any small insects feeding on the plant
  • It may also scare off animals trying to eat it
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Abiotic stress? (2)

A
  • Anything harmful that’s natural but non-living like a drought
  • Some plants respond to extreme cold by producing their own form of antifreeze
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Antifreeze? (2)

A
  • Carrots produce antifreeze proteins at low temperatures
  • The proteins bind to ice crystals and lower the temperature that water freezes at which stops more ice crystals from growing
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Tropism? (2)

A
  • A tropism is the response of a plant to a directional stimulus
  • Plants respond to stimuli by regulating their growth
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Positive tropism? (1)

A
  • Growth towards the stimulus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Negative tropism? (1)

A
  • Growth away from the stimulus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Phototropism? (3)

A
  • Growth of a plant in response to light
  • Shoots are positively phototropic and grow towards light
  • Roots are negatively phototropic and grow away from light
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Geotropism? (3)

A
  • Growth of a plant in response to gravity
  • Shoots are negatively geotropic and grow upwards
  • Roots are positively geotropic and grow downwards
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Hydrotropism? (2)

A
  • Plant growth in response to water
  • Roots are positively hydrotropic
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Thermotropism? (1)

A
  • Plant growth in response to temperature
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Thigmotropism? (1)

A
  • Plant growth in response to contact with an object
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How do plants respond to stimuli? (1)

A
  • By using growth hormones
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Growth hormones? (3)

A
  • Chemicals that speed up or slow down plant growth
  • Produced in the growing regions of the plant and they move to where they’re needed in the other parts of the plant
  • Also called growth substances
23
Q

Types of growth hormones? (2)

A
  • Gibberellin
  • Auxins
24
Q

Gibberellin? (1)

A
  • Gibberellin stimulates seed germination, stem elongation, side shoot formation and flowering
25
Q

Auxins? (2)

A
  • Stimulate the growth of shoots by cell elongation
  • High concentrations of auxins inhibit growth in roots
26
Q

Elongation? (1)

A
  • Cell walls become loose and stretchy, so the cells get longer
27
Q

Indoleacetic Acid (IAA)? (5)

A
  • Auxin produced in the tips of shoots in flowering plants
  • Stimulates cell elongation
  • IAA is moved around the plant to control tropisms
  • This results in different parts of the plants having different amounts of IAA
  • The uneven distribution of IAA means there’s uneven growth of the plant
28
Q

What are the uneven growths of a plant caused by uneven distribution of IAA? (2)

A
  • Phototropism: IAA moves to the more shaded parts of the shoots and roots, so there’s uneven growth
  • Geotropism: IAA moves to the underside of shoots and roots, so there’s uneven growth
29
Q

How do IAA move across a plant? (2)

A
  • Diffusion and active transport over short distances
  • Via the phloem over long distances
30
Q

What are auxins involved in? (2)

A
  • Apical Dominance
  • The growth of the apical bud is dominant over the lateral buds
31
Q

Apical bud? (1)

A
  • The shoot tip at the top of a flowering plant
32
Q

Auxins and apical buds? (2)

A
  • Auxins stimulate growth of apical bud
  • Auxins inhibit growth of side shoots from lateral buds
33
Q

Why is apical dominance important? (3)

A
  • Prevents side shoots from growing
  • This saves energy & prevents side shoots from same plant competing with the shoot tip for light
  • Allows a plant in an area where there are loads of other plants to grow tall very fast to reach the sunlight
34
Q

What happens if you remove the apical bud? (2)

A
  • The plant won’t produce auxins
  • Side shoots will start growing by cell division and cell elongation
35
Q

How can you demonstrate that apical dominance is controlled by auxin? (2)

A
  • Replace the tip with a source of auxin
  • Side shoot development is inhibited
36
Q

What happens to the concentration of auxin as they move away from the apical bud? (2)

A
  • At the bottom of the plant auxins become less concentrated
  • Side shoots will start to grow
37
Q

Gibberellins? (3)

A
  • Produced in young leaves and in seeds
  • Stimulate seed germination, stem elongation, side shoot formation and flowering
  • Don’t inhibit plant growth in any way
38
Q

Role of gibberellins in stem elongation? (2)

A
  • Help plants to grow tall
  • If dwarf variety of plant is treated with gibberellins then it will grow to the height of tall variety
39
Q

How do gibberellins stimulate seed germination? (2)

A
  • By triggering the breakdown of starch into glucose in the seed
  • The plant embryo in the seed then use the glucose to begin respiring and release the energy it needs to grow
40
Q

How can seed germination be prevented? (1)

A
  • Gibberellins are inhibited by the hormone abscisic acid
41
Q

Auxins and gibberellins are synergistic? (2)

A
  • They work together to have a really big effect
  • Auxins and gibberellins work together to help plants grow tall
42
Q

Auxins and gibberellins are antagonistic? (2)

A
  • They oppose each other’s actions
  • Gibberellins stimulate the growth of side shoots but auxins inhibit the growth of side shoots
43
Q

Deciduous plants? (1)

A
  • Plants that lose their leaves in winter
44
Q

Why is losing leaves helpful for deciduous plants? (3)

A
  • Helps plants to conserve water during the cold part of the year
  • Difficult to absorb water from frozen soil
  • There’s less light for photosynthesis
45
Q

Abscission? (2)

A
  • Leaf loss
  • Triggered by the shortening day length in autumn
46
Q

Role of auxins in abscission? (3)

A
  • Inhibit leaf loss
  • Auxins are produced by young leaves
  • As the leaf gets older, less auxin is produced, leading to leaf loss
47
Q

Role of ethene in abscission? (6)

A
  • Stimulates leaf loss
  • Ethene is produced by ageing leaves
  • As the leaves get older, more ethene is produced
  • Abscission layer develops at the bottom of the leaf stalk
  • Ethene stimulates cells in the abscission layer to expand
  • This breaks the cell walls and causing the leaf to fall off
48
Q

How do plants reduce water lost through transpiration? (1)

A
  • Close their stomata using guard cells
49
Q

Role of guard cells in reducing water loss? (3)

A
  • Guard cells found on either side of a stomatal pore
  • When the guard cells are full of water, they are turgid and the pore is open
  • When the guard cells lose water, they are flaccid and the pore closed
50
Q

What hormone is responsible for making the pore close? (1)

A
  • Abscisic acid (ABA) triggers stomatal closure
51
Q

How does ABA work? (7)

A
  • Binds to receptors on the guard cell membranes
  • Causes ion channels to open
  • Ca2+ enters cytosol from vacuole
  • Increased concentration of Ca2+ in cytosol causes other ion channels to open
  • This allows ions to leave the guard cells & raises the water potential of the cells
  • Water then leaves the guard cells by osmosis
  • Guard cells become flaccid and stomata closes
52
Q

Ethene’s use in the fruit industry? (2)

A
  • Stimulates enzymes that breaks down cell walls, chlorophyll and convert starch into sugars
  • Makes the fruit soft, ripe and ready to eat
53
Q

Auxins’ use as a weed killer (herbicides)? (2)

A
  • Make weeds produce long stems instead of lots of leaves
  • Make weeds grow too fast - they can’t get enough water or nutrients so they die
54
Q

Auxins’ use as a rooting hormone? (3)

A
  • Auxins make a cutting grow roots
  • Cutting can be planted and grown into a new plant
  • Cuttings can be taken from one original plant and treated with rooting hormones so lots of the same plant can be grown quickly and cheaply from just one plant

Biology (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions