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IB Biology > 9.3 Growth in plants > Flashcards

9.3 Growth in plants Flashcards

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1
Q

What are meristems?

A

Meristems are tissues in a plant consisting of undifferentiated cells capable of indeterminate growth

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2
Q

Why are meristems different to totipotent stem cells?

A

They have specific regions of growth and development

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3
Q

What can meristematic tissue cause?

A

Plants to regrow structures or even form new plants

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4
Q

What are the two types of meristems?

A

Apical meristems and Lateral meristems

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5
Q

Where do apical meristems occur?

A

At shoot and root tips

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6
Q

What are apical meristems responsible for?

A

Primary growth (plant lengthening)

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7
Q

Where do lateral meristems occur?

A

At the cambium

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8
Q

What are lateral meristems responsible for?

A

Secondary growth (plant thickening/ widening)

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9
Q

What do apical meristems produce?

A

New leaves and flowers

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10
Q

What do lateral meristems produce?

A

Bark

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11
Q

What causes the growth of apical meristems at the tips of the roots and shoots?

A

A combination of mitosis and cytokinesis

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12
Q

What does differentiation of the dividing meristem cause?

A

A variety of stem tissues and structures like leaves and flowers

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13
Q

Where does growth occur in the the stem?

A

In the nodes

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14
Q

What happens to the remaining meristem tissue?

A

They form an inactive axillary bud

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15
Q

What do lateral axillary buds have the potential to do?

A

Form new branching shoots, compete with leaves and flowers

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16
Q

What controls the growth of the stem and formation of new nodes?

A

Plant hormones

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17
Q

Where are the plant hormones released from?

A

The shoot apex

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18
Q

What are auxins?

A

One of the main groups of plant hormones involved in shoot and root growth

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19
Q

What happens when auxins are produced by the shoot apical meristem?

A

It promotes growth in the shoot apex via cell elongation and division

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20
Q

What does the production of auxin prevent?

A

Apical dominance - growth in lateral axillary buds

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21
Q

What does apical dominance do?

A

Makes sure that a plant uses its energy to grow up towards the light in order to outcompete other plants

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22
Q

What happens when the distance between the terminal bud and axillary bud increases?

A

The inhibition of the axillary bud by auxin diminishes

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23
Q

What will different species of plants show?

A

Different levels of apical dominance

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24
Q

What can auxin efflux pumps set up?

A

Concentration gradients within tissues which change the distribution of auxin within the plant

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25
Q

What can auxin efflux pumps control and how?

A

The direction of plant growth by determining which regions of plant tissue have high auxin levels

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26
Q

Why can auxin efflux pumps do?

A

Change position within the membrane due to fluidity

Be activated by different factors

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27
Q

In shoots what does auxin do to cell elongation?

A

Stimulates it

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28
Q

What does high concentration of auxin in shoots do?

A

Promotes growth

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29
Q

In roots what does auxin do to cell elongation?

A

Inhibit it

30
Q

What does high concentration of auxin in roots do?

A

Limit growth

31
Q

How does auxin influence cell growth rates?

A

By changing the pattern of gene expression within a plants cells

32
Q

Why are auxins mechanism of action different in shoots and roots?

A

As different gene pathways are activated in each tissue

33
Q

In shoots how does auxin promote plant growth via cell elongation?

A

By increasing the flexibility of the cell wall

34
Q

What does auxin activate in the plasma membrane?

A

A proton pump which causes the secretion of H+ ions into the cell wall

35
Q

What does the decrease in pH caused by auxin result in?

A

Cellulose fibres within the cell wall to loosen by breaking the bonds between them

36
Q

What does auxin upregulate?

A

The expression of expansins which increase cell wall elasticity

37
Q

As the cell wall is more flexible what does that cause?

A

An influx of water causing the cell to increase

38
Q

What is tropisms?

A

The growth or turning movement of a plant in response to a directional external stimulus

39
Q

What is phototropism?

A

A growth movement in response to a unidirectional light source

40
Q

What is geotropism/gravitropism?

A

A growth movement in response to gravitational forces

41
Q

What is hydrotropism?

A

A growth movement in response to a water gradient

42
Q

What is thigmotorpism?

A

A growth movement in response to a tactile stimulus

43
Q

What are both phototropism and geotropism controlled by?

A

The distribution of auxin in the plant cells

44
Q

Where will auxin accumulate in geotropism and why?

A

On the lower side of the plant in response to the force of gravity

45
Q

What triggers auxin in phototropism?

A

Light receptors called phototropins

46
Q

What do phototropins trigger?

A

The redistribution of auxin to the dark side of the plant

47
Q

What happens on the dark side of the shoot in phototropism?

A

The dark side of the shoot elongates and shoots grow towards the light

48
Q

What happens on the lower side of the shoot and the roots in phototropism?

A

The lower side of the shoot elongates and roots grow away from the ground

49
Q

What happens on the dark side of the root in phototropism?

A

The dark side of the root becomes shorter and the roots grow away from the light

50
Q

What happens on the light side of the root in phototropism?

A

The lower side of the root becomes shorter and the roots turn downwards into the earth

51
Q

Where does negative phototropism occur?

A

The roots

52
Q

Where does positive phototropism occur?

A

The shoots

53
Q

What is micropropagation?

A

A technique used to produce large numbers of identical plants

54
Q

Why can plants reproduce asexually from meristems?

A

Because they are undifferentiated cells capable of indeterminate growth

55
Q

What is vegetative propagation?

A

When a plant cutting is used to reproduce asexually in the native environment

56
Q

What is it called when plant tissues are cultured in the laboratory in order to reproduce asexually?

A

Micropropagation

57
Q

What is selected during the micropropagation?

A

Specific plant tissue from a stock plant which is then sterilised

58
Q

What is the explant?

A

The tissue sample

59
Q

Where is the tissue sample during micropropagation grown?

A

On a sterile nutrient agar gel

60
Q

What is the explant treated with and why?

A

It is treated with growth hormones to stimulate shoot and root development

61
Q

What happens to the growing shoots in micropropagation?

A

They can be continuously divided and separated to form new samples

62
Q

During micropropagation, what happens once the root and shoot developed?

A

The cloned plant can be transferred to soil

63
Q

Why is micropropagation used?

A

To rapidly produce large numbers of cloned plants under controlled conditions

64
Q

What are the three reasons to use micropropagation?

A

Rapid bulking
Virus free strains
Propagation of rare species

65
Q

Why are desirable stock plants cloned via micropropagation?

A

To conserve the fidelity of the selected characteristics

66
Q

Why is micropropagation more reliable than selective breeding?

A

Because new plants created are genetically identical to the stock plant

67
Q

How do plant viruses spread through infected plants?

A

Via the vascular tissue

68
Q

How can propagating plants prevent viruses?

A

Propagating plants from non infected meristems allows for the rapid reproduction of virus free plant strains

69
Q

What does micropropagation do for rare species?

A

Increases the number of them

70
Q

Why does micropropagation help orchids?

A

Because they are difficult to breed sexually

71
Q

What helps increase numbers of species commercially in demand?

A

Micropropagation

IB Biology (57 decks)

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