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A Level Biology - 5.1.5 Plant responses > Control of plant growth > Flashcards

Control of plant growth Flashcards

1
Q

What is the communication pathway in plants?

A

Environment -> Sensory input -> Cell signalling -> Output

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2
Q

Where is plant division limited to?

A

Meristems

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3
Q

What is the main meristem?

A

The shoot apical meristem for primary growth

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4
Q

What is the main meristem found?

A

The top of the stem

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5
Q

What is the main growing root?

A

The root apical meristem for primary growth

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6
Q

Where is the main growing root found?

A

The tip of the roots

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7
Q

What is found in the meristem?

A

A zone of elongation and then division

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8
Q

What is the lateral meristem?

A

Allows with of shoots and roots to increase (cambium) for secondary growth

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9
Q

Where is the lateral meristem?

A

Outside of shoots and roots

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10
Q

What is primary growth?

A

Getting longer

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11
Q

What is secondary growth?

A

Getting wider

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12
Q

What is the intercalary meristem?

A

Increases the distance between leaves

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13
Q

Where is the intercalary meristem?

A

Between nodes

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14
Q

What are the main meristem?

A

Shoot apical, root apical, lateral and intercalary

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15
Q

What controls plant growth?

A

Tropism, apical dominance and stem elongation

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16
Q

What coordinates plant growth?

A

Plant hormones

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17
Q

How do plant hormones move?

A

By active transport, diffusion or phloem/xylem (mass flow)

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18
Q

What is needed for plant hormone to move?

A

Incredibly low concentrations

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19
Q

How are plant hormones produced?

A

By specific cells

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20
Q

What is specific about plant hormones?

A

Their shape

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21
Q

How do plant hormones act?

A

They bind to a receptor on/in the target cell which is complementary to the shape of the hormone

22
Q

What is the effect of plant hormone action?

A

Specific genes that promote growth are turned on

23
Q

What are tropisms?

A

A directional plant growth response to a directional stimuli

24
Q

What is the result of phototropism?

A

Shoot grows up towards light no rots grow down

25
Q

What is phototropism?

A

A growth response to light controlled by auxin

26
Q

What is geotropism?

A

A growth response to gravity controlled by auxin

27
Q

What is the result of geotropism?

A

Roots grow down into soil and shoots grow up

28
Q

What does etiolated mean?

A

Tall and thin

29
Q

Where are auxins found?

A

They are produced a very high concentrations in the shoot tip and are transported down the shoot

30
Q

How does auxin lead to growth?

A
  1. Auxin is made at apex
  2. Auxin diffuses or is actively transported to zone of elongation
  3. Auxin binds to receptors on cells in zone of elongation
  4. This triggers active transport of hydrogen ions into the cell wall.
  5. Leads to high hydrogen ion concentration and low pH in cell wall
  6. High hydrogen ion conc, breaks hydrogen bonds holding cellulose molecules together within fibres
  7. Cell wall is less rigid
  8. Drop in pressure potential
  9. Water enters cell by osmosis and cell elongates
31
Q

What is the coleoptile?

A

A sheath that protects a young shoot tip found in grasses and cereals

32
Q

What did Darwin investigate?

A

The phototropic response when tip isn’t illuminated

33
Q

How does geotropsim work?

A

Auxin is produced at the tip and drops to the bottom due to gravity

34
Q

How do you investigate geotropism?

A

Using a clinostat which removed the effect of gravity as it rotates

35
Q

What is apical dominance?

A

The presence of a main growing shoot

36
Q

What is the result of apical dominance?

A

Less of the plant is shaded

37
Q

What is the effect of apical dominance?

A

The terminal bud contains auxin which inhibits growth of lateral buds

38
Q

What is apical bud decapitation?

A

Removal of the terminal bud via selective pruning

39
Q

What is the effect of apical bud decapitation?

A

The dormant lateral buds develop, producing bushier plants

40
Q

What happens to the auxin when the apical bud is cut off?

A

Auxin levels drop and new branches grow

41
Q

What happens if you put chemicals on the apical bud?

A

Transport can be inhibited and new branches will grow from the lateral and apical bud

42
Q

What does auxin do the abscisic acid?

A

Keep levels high

43
Q

What happens if you add cytokines to the lateral buds?

A

New branches will grow to override effect of auxin

44
Q

What is the effect of gibberellins?

A

Stem elongation at internodes and is structurally based on terpenes

45
Q

Where are gibberellins found?

A

Young and expanding shoots, buds, root tips and seeds

46
Q

How do gibberellins move?

A

Up and down plants through xylem and phloem

47
Q

What do gibberellins stimulate?

A

Mitosis in the intercalary meristem in the internodes so can convert dwarf plants to normal sizes and grow

48
Q

What happens when you apply giberellins?

A

Plants bold and produce flowers in the 1st season with larger internodes

49
Q

What happens when you increase concentration of gibberellins?

A

Increased growth

50
Q

What are uses of auxins?

A

Weed killers and rooting powder

51
Q

How does auxin work as a weed killer?

A

Weeds ar broad leaved plants that absorb a lot of hormone so they grow out of control, use up all nutrients and die

52
Q

How is auxin used as rooting powder?

A

It stimulates cell growth

A Level Biology - 5.1.5 Plant responses (2 decks)

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