Brainscape's Knowledge GenomeTM

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


See full index

Alevel Biology OCR A > 5.1.5 Plant Responses COMPLETE > Flashcards

5.1.5 Plant Responses COMPLETE Flashcards

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

Directional plant growth

A

Known as tropisms and are controlled by plant hormones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Non Directional plant growth

A

Known as Nastic Responses and are not controlled by hormones. They are fast and controlled by temporary changes in the cells such as turgidity.
Examples: Venus Fly Trap

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Responses to Herbivory

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

Chemical Defences

A

ALKALOIDS- Bitter toxic chemicals
TANNINS- Binds to digestive enzymes
TERPENOIDS- Smell may deter insects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Pheromones

A

Chemicals produced by an individual to affect the behaviour of another, damaged plants create them so that other plants build their defences.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Thigmonasty

A

Move quickly in response to touch, sudden folding of leaves may dislodge small insects and scare others.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Responses to Abiotic Stress

A
  • Leaves fall in autumn
  • Antifreeze production, genes are switched on to produce antifreeze proteins which stop crystallisation
  • Stomatal Closure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Tropisms

A

Geotropism
Phototropism
Chemotropism
Thigmotropism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Geotropism

A

Roots show positive and shoots grow away from gravity so is negative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Phototropism

A

Shoots grow towards the light, positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Chemotropism

A

Pollen tubes grow towards chemicals directing them to the ovary.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Thigmotropism

A

Winding around a structure as seen in climbing plants.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Features of plant hormones

A
  • Produced in a variety of tissues
  • Move by active transport, diffusion, mass flow
  • Bind to complimentary receptors
  • Slow
  • Permanent changes
  • Present in small quantities
  • Work antagonistically and synergistically
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Auxins

A

Promote cell elongation
Inhibits the growth of side shoots
Inhibits leaf abscission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Cytokinins

A

Promote cell division

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Gibberellins

A

Causes stem elongation

Promotes seed germination

17
Q

Abscisic Acid

A

Maintains seed and bud dormancy
Stimulates stomatal closure
Stimulates antifreeze

18
Q

Ethene

A

Promotes fruit ripening

Promotes leaf abscission

19
Q

Role of the plant tip

A

Required for growth
Where light is sensed for phototropism
When tip is removed or shaded it doesn’t grow towards light

20
Q

Effect of the addition of a mica sheet

A

Found that auxin does down shaded side of the plant

When the sheet blocks the shaded side the curvature stops but continues if the illuminated side is blocked.

21
Q

Effect of gelatine when inserted in a cut tip

A

Jelly allows normal growth and a repose to light as the auxin can diffuse through it still.

22
Q

Effect of soaking agar in auxin

A

The coleoptile bends even in the dark

The angle increases alongside the concentration of auxin however then begins to decrease again

23
Q

Auxins

A

Made in the meristem near tips

Causes plant elongation

24
Q

How auxins work

A

Bind to receptors on the cell surface membrane and promotes the active transport of H+ ions into the cell walls
Causes a drop in pH making it more acidic
This weakens cellulose bonds and activates enzymes that breaks them down more
As water is taken in by osmosis the cell permanently elongates as cell wall is weakened
As cell matures auxins are destroyed and cell wall becomes rigid again.

25
Q

Auxins and Phototropism

A

Cells in the shoot and tip contain PHOTOTROPINS
When hit by blue light they become phosphorylated causing auxin produced in the shoot to be moved into the shade
So the cell therefore bends/ elongates

26
Q

Different effects of auxins

A

In the stem auxins gather at the bottom and stimulates growth so it bends up
In the root auxin gathers at the bottom and inhibits growth so it bends down

27
Q

Apical Dominance

A

A region near the top of the terminal bud contains the apical meristem
This shows dominance over the lateral buds
The plant therefore grows straight up and can compete for light
If the tip is cut off then the lateral buds start growing and it bushes out

28
Q

Control of apical dominance

A

Auxin is made in the apical bud where it causes cell elongation
It diffuses down to the lateral buds where it inhibits them
Its thought the auxins keeps levels of abscisic acid high in the lateral buds which inhibits growth, when cytokinins applied it’ll override the inhibition

29
Q

Gibberellins Details

A

Produced in young leaves and stems and cause growth of the stem in the internodes
Works by affecting gene expression
Causes cell division and cell elongation
SYNERGISTIC- Plant grows tall
ANTAGONISTIC- Auxin inhibits side shoots

30
Q

Gibberellins and Germination

A

When water is absorbed the embryo releases gibberellin
Travels to the aleurone layer in the endosperm of the seed
This switches on genes which codes for amylases and proteases
Stored starch is hydrolysed into glucose providing a substrate for respiration so the embryo can grow

31
Q

Leaf abscission in Deciduous Plants

A

In winter theres less light and lower temp so less photosynthesis
Water is lost through leaves, exposure to fungal infection and frost damage means its best to lose leaves

32
Q

Abscission explained

A

Reduced light means less auxin and balance shifts to there being more ethene which causes ageing.
This stimulates enzymes to weaken thin walls and the cellulose bonds are broken
A layer of Suberin develops underneath for protection
Vascular bundles are sealed off and the leaf is blown away by the wind

33
Q

Role of Abscisic acid

A

-Plants produce ABA under abiotic stress to close the stomata which helps reduce transpiration

34
Q

Effect of Abscisic acid

A

ABA binds to receptors on the cell surface membrane on the guard cells
Ca2+ enters the cell causing K+ to leave
Water potential in the cell increases
Water leaves by osmosis
Guard cells become flaccid and close the stomata

35
Q

Commercial use of Auxin

A
  • Selective weed killer
  • Used in cuttings to grow roots
  • Seedless fruits
36
Q

Commercial use of Gibberellins

A
  • Improve plant shape
  • Delay fruit ripening
  • Larger grapes
  • Longer sugar canes
37
Q

Commercial use of Cytokinins

A
  • Stops lettuces going yellow once packaged

- Causes shoot growth in tissue culture

38
Q

Commercial use of Ethene

A
  • Causes fruit to drop at a certain time
  • Speeds up the ripening process
  • Promotes female flowers

Alevel Biology OCR A (26 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions