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Biology 1 > Regulatory mechanisms in Plants > Flashcards

Regulatory mechanisms in Plants Flashcards

1
Q

In plants, what is the primary organ of photosynthesis?

A

Plant leaves

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2
Q

What is the purpose of pores in plants?

A

They allow CO2 in and O2 out (air movement for gas exchange)

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3
Q

What is another name of pores?

A

Stomata

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4
Q

What is the problem with stomata being open?

A

Allows water vapour to escape

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5
Q

What is the loss of water vapour called?

A

Transpiration

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6
Q

How do plants minimise water losses?

A

By using guard cells to open and close stomata at certain times of the day

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7
Q

What do stems in plants do?

A

Supports leaves and transports organic materials (sugars), ions and water between the root and the leaves

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8
Q

What is at the top of each stem?

A

Terminal bud

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9
Q

What is at the axis of each new leaf?

A

Axillary bud

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10
Q

Where does mitosis occur in plants?

A

The terminal bud and axillary bud

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11
Q

What is the definition of stomata?

A

The pores through which gas exchange occurs

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12
Q

Where is the stomata usually found?

A

The epidermis (outer most layer of plants) of the leaf

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13
Q

What does each stoma consist of?

A

Two elongated guard cells

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14
Q

What causes a change in the stomata being open or closed?

A

Change in turgor pressure of the guard cells

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15
Q

What is the status of the stoma when then guard cells are turgid?

A

Pores open

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16
Q

What is the status of the stoma when then guard cells are flaccid?

A

Pores closed

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17
Q

When are stomata usually open?

A

During the day

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18
Q

When are stomata usually closed?

A

During the night

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19
Q

What is the environment of a saguaro cactus?

A

Harsh desert

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20
Q

What are the skin adaptations of the saguaro cactus?

A

Skin is covered with a thick, wavy coating that is waterproof, thus reducing water loss via transpiration

Skin is covered with hard spines and flexible bristles, which defend the water stored inside

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21
Q

How do plants replace water losses through transpiration?

A

Transporting water from the roots to the leaves

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22
Q

What does the root system provide?

A

Huge surface area to take in water

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23
Q

What are the three forces water in plants is under in xylem tubes?

A
  1. A pulling force by transpiration in leaves
  2. A pushing force exerted by osmosis and entry of water into root hair cells
  3. Adhesion and cohesion forces of water molecules (work against gravity)
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24
Q

What is the transpiration stream?

A

A unbroken water of water travelling from roots to leaves in xylem tubes, generated by the three forces

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25
Q

How is osmosis involved in the process of transporting water?

A

The water from the soil osmoses into the roots, which starts the whole process. The root system creates a massive surface area in which the plants draw in essential ions and water. This high SA is created by root hairs, extensions of epidermal cells that are short lived

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26
Q

What allows the water to transport under tension?

A

The cohesive property of water and the structure of xylem vessels

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27
Q

What is a xylem vessel?

A

A long, hollow tube composed of xylem cells

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28
Q

What the features of xylem cells?

A

Dead at functional maturity.
No cellular components (cytoplasm, membranes, etc)/

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29
Q

What are the types of processes that create the flow of water along xylem vessels?

A

Passive processes

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30
Q

What is the difference in pressure between inside xylem vessels and the atmosphere?

A

The pressure inside xylem vessels is usually much lower than atmospheric pressure

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31
Q

What are the features of the walls of xylem vessels?

A

They are thickened and contain the polymer lignin, which strengthens the walls (so they can withstand very low pressures without collapsing inwards)

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32
Q

Are water molecules polar or non-polar?

A

Polar

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33
Q

Why do water molecules exhibit cohesion between each other?

A

Hydrogen bonding

34
Q

When do water molecules exhibit adhesion?

A

To hydrophilic cellulose fibres in xylem walls (due to hydrogen bonding)

35
Q

What occurs as a result of connections between water molecules, and between water and the xylem vessels?

A

Water can be pulled up in a continuous stream

36
Q

What is the size of xylem tubes?

A

Very thin, microspoic

37
Q

What is the effect of the xylem tubes being small?

A

A very small amount of water can move a long distance within it

38
Q

What generates tension forces in leaf cell walls?

A

Adhesive property of water and evaporation

39
Q

What happens when water evaporates from the surface of a cell wall in a leaf?

A

Adhesion causes the water to be drawn through the cell wall to replace the transpiraton. The nearest available source is xylem vessels in leaf veins

40
Q

How does water move betweeen cells?

A

osmosis

41
Q

What is a transpiration pull?

A

A force generated by a low internal pressure of xylem vessels. It is transmitted through the water in the xylem vessels down the stem and to the ends of the xylem in the roots

42
Q

What causes a low internal pressure of xylem vessels?

A

Evaporation of water from leaves and the resulting movement of water out of the xylem

43
Q

What is the only energy required to drive the transpiration process?

A

Heat change that causes evaporation and leads to transpiration

44
Q

What are the two pathways water can take to reach the xylem?

A

Cytoplasmic/symplastic pathway + extracellular/apoplastic pathway via cell walls

45
Q

How can mineral ions enter the plants’ systems?

A

Can be absorbed by active transport or when they dissolve into water and diffuse

46
Q

How does light affect transpiration?

A

It is essential for water vapour to be lost through evaporation

47
Q

What does an increase in light lead to?

A

An increase in transpiration

48
Q

What does an increase in temperature lead to?

A

An increase in transpiration

49
Q

How does temperature affect transpiration?

A

Causes the evaporation of water molecules

50
Q

How does wind affect transpiration?

A

Moves water molecules away from stomata, increasing water concentration gradient

51
Q

What does increased wind lead to?

A

Increase transpiration

52
Q

How does humid air affect transpiration?

A

Decreases water vapour gradient

53
Q

What does high humidity lead to?

A

Decreased transpiration

54
Q

What are xerophytes?

A

Organisms that live in environments characterized by water scarcity and shortage

55
Q

Which plants are highly adapted to water scarcity and shortage?

A

Desert plants

56
Q

What is water in plants needed for?

A

Support, photosynthesis, transport, cooling, enzyme action

57
Q

What are the adaptations of xerophytes focused on?

A

Increased rate of water uptake from soil + reducing the rate of water loss by transpiration

58
Q

Why do some xerophytes have short reproductive cycles?

A

To take advantage of what short periods of rain there might be

59
Q

What is translocation?

A

The movement of manufactured food (sugars, amino acids, etc)

60
Q

Where does translocation occur?

A

In the phloem tissue of vascular bundles

61
Q

Where does translocation first go to?

A

Areas of new growth. As the plant ages, it is increasingly transported to sites of storage

62
Q

Where are amino acids mainly made?

A

In the roots

63
Q

Where are amino acids transported to?

A

Sites of protein synthesis

64
Q

What does phloem tissue have a relatively high rate of during transport?

A

Aerobic respiration, as translocation is an active process

65
Q

Where do water and solutes travel?

A

Down the hydrostatic gradient to the sink (root cell) where pressure is low.

66
Q

Why do root cells (the sink) have low pressure?

A

Active unloading of sucrose: thus loss of water via osmosis

67
Q

Why do plants have long roots?

A

Long roots help anchor plant to the sandy desert, preventing it from being rooted out by the wind. Also helps with osmosis and water uptake

68
Q

What is the survival advantage of having extremely reduced leaves becoming spines?

A

Reduced leaf area for transpiration and protection against animals

69
Q

What is the survival advantage of green stems (due to photosynthetic cells in stem tissue)?

A

Cells carry out photosynthesis to compensate for the reduced leaf size and area

70
Q

What is the survival advantage of pleats in the stem?

A

Allows expansion when water storage tissue expands

71
Q

What is the survival advantage of stems that contain water storage tissue?

A

Stores water during rainfall to keep plants alive during periods of dryness

72
Q

What is the survival advantage of having a thick waxy cuticle?

A

Prevent movement of water out of epidermis

73
Q

What is the survival advantage of stomata in plant stems (through more widely-spaced than in leaves)?

A

Allows movement of gases necessary for photosynthesis and respiration

74
Q

What is the survival advantage of having stomata open at night?

A

Transpiration occurs more slowly in cooler temperatures

75
Q

What is the survival advantage of CO2 being absorbed at night (then stored as malic acid - a four-carbon compound)?

A

CO2 can be released from malic acid during the day, so stomata can remain closed

76
Q

What is an adaptation specific to Marram grass?

A

Their leaves roll up to limit water loss, which deals with the drying effects of the wind and tolerating the poor water retention of the soil

77
Q

How is the stomata put into an enclosed space with Marram grass?

A

The thick, waxy epidermis extends all the way around as the leaf rolls ups. This prevents the stomata from being near the wind

78
Q

Where are the stomata located in Marram grass?

A

They are in pits which allows boundary layers of humidity to build up, reducing water loss by evaporation

79
Q

What is the effect of having hairs on the inner surface (Marram grass)?

A

Allows water vapour to be retained, reducing water loss through pores

80
Q

What does the groove formed by the rolled leaf (Marram grass) do?

A

Acts as a channel for rainwater to drain directly to the specific root of the grass stem

81
Q

Where do the sugars of translocation move to?

A

Flow down the hydrostatic gradient to the sink where the pressure is relatively low.

Biology 1 (10 decks)

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