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A Level Biology OCR > 5.5 Plant Responses > Flashcards

5.5 Plant Responses Flashcards

1
Q

What do tannins do?

A
  • Make leaves taste bad

- Make roots less easy for pathogens to enter

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2
Q

What is the difference between biotic and abiotic environmental components?

A

Biotic=Living

Abiotic=Non-living

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3
Q

Why must plants respond to their environment?

A

It may help them live long enough to reproduce

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4
Q

What are alkaloids?

A

Nitrogenous bases that have physiological effects on animals e.g. nicotine

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5
Q

What is a pheromone?

A

A signalling chemical that can produce a response in another organism.

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6
Q

What is a tropism?

A

A directional growth response in which the direction of the response is determined by the direction of the external stimulus

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7
Q

What is phototropism and why is it needed?

A

Plant shoots grow towards light, enabling them to photosynthesise

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8
Q

What is geotropism and why is it needed?

A

Roots grow towards gravity’s pull, allowing them to be anchored to the soil and take up water and minerals

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9
Q

What is thigmotropism and why is it useful?

A

Shoots climbing plants, such as ivy, wind around other plants or structures for support

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10
Q

What is a nastic

response?

A

Non directional response to external stimuli

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11
Q

What is a negative tropic response?

A

A plant responding away from a stimulus

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12
Q

What are plant hormones?

A

Chemical messengers that can be transported away from where they are made to act in other parts of the plant.

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13
Q

How can you ensure that hormones only act upon the correct tissues?

A

Specific hormones bind to specific receptors with complementary shapes on the membranes of particular cells

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14
Q

What are the effects of cytokinins?

A
  • Promote cell growth
  • Delay leaf ageing
  • Overcome apical dominance
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15
Q

What are the effects of abscisic acid?

A
  • Inhibits seed germination and growth

- Causes stomatal closure

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16
Q

What are the effects of auxins?

A
  • Promote cell elongation
  • Promote apical dominance
  • Inhibit leaf abscission (fall)
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17
Q

What are the effects of gibberellins?

A
  • Promote seed germination

- Stem elongation

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18
Q

What is the effect of ethene?

A

Promotes fruit ripening

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19
Q

How do hormones move long distances around the plant?

A

Mass flow in phloem or xylem

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20
Q

What is apical dominance?

A

Inhibition of lateral bud growth by auxins.

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21
Q

What does rooting powder do?

A

Encourage root growth

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22
Q

What does rooting powder contain?

A

Auxins and talcum powder

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23
Q

What would happen to the plant if there wasn’t any apical dominance?

A

The plant would grow in all directions, becoming bushy, and photosynthesis wouldn’t be efficient enough.

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24
Q

Why can’t plant cells divide as readily as animal cells?

A

They are limited by the cellulose cell wall

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25
Q

What are meristems?

A

A particular place in the plant where there are still groups of immature cells capable of dividing

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26
Q

Which plant hormone causes stomatal closure at times of water stress?

A

Abscisic acid

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27
Q

What hormone causes seed germination?

A

Gibberellins

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28
Q

What hormone effects leaf loss?

A

Auxins

29
Q

What are expansins?

A

Cellulose cell wall loosening enzymes

30
Q

What pH is optimum for expansins?

A

Acidic (low pH)

31
Q

What plant hormone causes cell elongation?

A

Auxins

32
Q

What plant hormone causes stem elongation?

A

Gibberellin

33
Q

How does gibberellin stimulate cell elongation?

A

By loosening cell walls

34
Q

How does gibberellin stimulate cell division?

A

By stimulating production of a protein that controls the cell cycle

35
Q

What is the difference between Auxin and Gibberellin in their growth effects?

A
  • Auxin controls tropic growth from nodes and buds

- Gibberellin controls stem elongation (growth in internodes)

36
Q

What does a DELLA protein do?

A

Binds to transcription factors, making them useless. It effectively stops protein synthesis and growth

37
Q

What are transcription factors?

A

Proteins that initiate gene transcription for protein synthesis

38
Q

How does cutting the tip of a shoot allow lateral growth?

A

When the tip with high auxin concentration is cut abscisic acid levels drop and growth is allowed in lateral buds.
(High abscisic acid=lateral growth inhibition)

39
Q

How does mimosa pudica respond to touch?

A

A signal is spread from the touched leaf causing it to quickly fold up to prevent mimosa pudica from being eaten.

40
Q

What is the function of IAA (Indoleacetic acid) ?

A

It moves around the plant to control tropisms, by stimulating cell elongation. It has an uneven distribution so that plant can grow unevenly.

41
Q

How does IAA (Indoleacetic acid) move around the plant for long distances?

A

Phloem tubes

42
Q

How does IAA help phototropism?

A

IAA moves to shaded parts of the shoots, making the cells on that side elongate and the shoot bends towards the light.

43
Q

How does IAA help geotropism?

A

IAA moves to the underside of shoots, making cells elongate and the shoot grows upwards.

44
Q

Why does covering the tip of a shoot make it grow straight upwards rather then towards the light?

A

The tip is most sensitive to light and because the tip is covered it’s not in contact with light so grows straight up

45
Q

When investigating geotropism, why must you insure your shoots are covered?

A

Because if light reaches the shoots this will effect your results due to phototropism.

46
Q

How do you investigate geotropism?

A

Have planted shoots and place them at different angles

47
Q

Why is it that in a tall plant, side shoots grow near the bottom?

A

The auxin concentration near the bottom is low so it’s effect of inhibiting side shoot growth is not effective

48
Q

Why do you need a control experiment?

A

You need something untreated so that you can compare and see if the effect from the independent variable is not from any other factor.

49
Q

How to gibberellins stimulate seed germination?

A

They trigger the breakdown of starch into glucose, which the seed embryo can use to respire and make energy to grow.

50
Q

Why does abscisic acid prevent seed germination?

A

Because it inibits gibberellin action

51
Q

What does synergistic mean?

A

When 2 things can work together to have a big effect e.g. auxin and gibberellins can work together to make a plant really tall

52
Q

What does antagonistic mean?

A

When 2 things oppose eachothers actions e.g. when gibberellins stimulate side shoots growth and auxins inhibit side shoots growth

53
Q

What is leaf abscission?

A

Leaf loss

54
Q

Why do deciduous plants lose leaves in the winter?

A

Helps to conserve water lost from their leaves during water stress- soil water may be frozen

55
Q

What triggers leaf loss?

A

Shortening day length in autumn

56
Q

How do auxins effect leaf loss?

A

They inhibit leaf loss

57
Q

How does ethene effect leaf loss?

A

Ethene promotes leaf loss

58
Q

What is the process of stomatal closure?

A

It opens ion channels which let the water potential inside the cell rise, so water leaves the cell by osmosis- this makes it flaccid closing the stomata.

59
Q

What is the process for fruit ripening?

A

Ethene stimulates enzymes which break down cell walls, chlorophyll, and starch into glucose.

60
Q

How can auxins be used in weed killers?

A

They make weeds grow long stems and grow too fast which they can’t supply so they die.

61
Q

What are the advantages of taking cuttings?

A

It’s quick, cheap and easy to keep taking cuttings from the same plant

62
Q

What is a coleoptile?

A

A seedling a few days after germination

63
Q

Where is the zone of max cell elongation?

A

Just below the tip

64
Q

How does auxin increase stretchiness of the plant cell wall?

A

By promoting active transport of H+ ions into the cell wall

65
Q

How do H+ loosen the plant cell wall?

A

They decrease the pH allowing expansin enzymes to work at their optimum

66
Q

How do expansins stretch cell walls?

A

They break bonds within the cellulose fibres, making the cell wall less rigid

67
Q

What are phototropins?

A

Proteins that act as receptors for blue light, found in meristematic cells

68
Q

Phototropins become _________ when hit by blue light.

A

Phosphorylated

69
Q

What is in a vascular bundle from inside outwards?

A

Xylem
Cambium
Phloem

A Level Biology OCR (28 decks)

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