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Biology > 7b. MASS TRANSPORT IN PLANTS > Flashcards

7b. MASS TRANSPORT IN PLANTS Flashcards

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1
Q

Name the two transport vessels in a plant

A

Xylem and Phloem

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2
Q

What is transported through the xylem, and in which direction?

A

Water and ions are transported up the plant

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3
Q

Describe the four structural features of a xylem vessel

A

Long tubes with no end walls
No organelles
Lignin
Bordered pits

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4
Q

Why are xylem long tubes with no end walls?

A

To allow a continuous stream of water to flow

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5
Q

Why do Xylem have no organelles?

A

So as not to obstruct the flow of water

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6
Q

Why are Xylem are surrounded by lignin?

A

To waterproof them

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7
Q

Why do Xylem have bordered pits?

A

To allow lateral movement of water

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8
Q

Name the theory by which water move up the xylem of a plant

A

Cohesion-tension theory

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9
Q

What is transpiration is driven by?

A

Evaporation from the stomata, which is driven by energy from the sun

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10
Q

As water evaporates from the stomata, describe the effect on the water potential of the mesophyll tissue

A

It reduces it

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11
Q

Which force causes water to be drawn up the xylem in one continuous column?

A

Cohesion

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12
Q

Which force draws the walls of the xylem inwards?

A

Tension

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13
Q

The tension in the xylem is caused by evaporation from the stomata, and which two forces acting together?

A

Cohesion and adhesion

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14
Q

Describe the pressure inside the xylem

A

It is more negative than the atmospheric pressure

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15
Q

Describe the relationship between the rate of evaporation from the leaf, and the amount of tension inside the xylem

A

As rate of evaporation increases, tension increases

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16
Q

Describe the relationship between the rate of evaporation and the pressure inside the xylem

A

As rate of evaporation increases, pressure becomes more negative

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17
Q

Name the five factors that affect the rate of transpiration

A

Temperature, humidity, light intensity, wind speed, number of stomata per area

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18
Q

Why does increasing temperature increase the rate of transpiration?

A

It would increase the KE of the particles

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19
Q

Why does increasing light intensity increase the rate of transpiration?

A

It would cause more stomata to open

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20
Q

Why does increasing humidity decrease the rate of transpiration?

A

It would decrease the water potential gradient between the inside and outside of the leaf

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21
Q

Why does increasing wind speed increase the rate of transpiration?

A

It would increase the water potential gradient between the inside and outside of the leaf

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22
Q

Describe the structure of the phloem

A

Sieve tube elements with sieve plates at either end. Attached to companion cells.

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23
Q

Describe the two adaptations of the phloem

A

No organelles, and thick walls.

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24
Q

Explain why the phloem has no organelles

A

To allow easier flow of dissolved sugars.

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25
Q

Explain why the phloem has thick walls

A

To withstand pressure.

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26
Q

How are the companion cells adapted to carry out their function?

A

They contain mitochodria to release energy for the active process of phloem loading.

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27
Q

What is translocation?

A

The movement of dissolved sugars from sources to sinks.

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28
Q

Why is sucrose translocated instead of glucose?

A

To prevent glucose being used in metabolic processes during translocation.

29
Q

Define what a source is

A

Where glucose is produced or stored.

30
Q

Give examples of a source

A

Leaves, tubers, tap roots

31
Q

Define what a sink is

A

Where glucose is used or stored.

32
Q

Give examples of a sink

A

Meristems, seeds, tubers, tap roots.

33
Q

Explain how something can be a source and also a sink

A

When dissolved sugars are translocated to the organ for storage it is acting as a sink. But when glucose is removed for use, it is acting as a source.

34
Q

How do sugars travel from the sources to the companion cells?

A

Diffusion

35
Q

How do sugars move from the companion cells to the phloem?

A

Active transport

36
Q

How does the introduction of sugars into the phloem affect the water potential inside the phloem?

A

It reduces it / makes it more negative

37
Q

What is the effect of the reduction of the water potential inside the phloem?

A

It causes water to move by osmosis from the xylem to the phloem down a water potential gradient

38
Q

How is the hydrostatic pressure inside the phloem increased?

A

More water is introduced into the phloem

39
Q

What is the effect of the increasing hydrostatic pressure inside the phloem?

A

It causes the dissolved sugars to move through the phloem by mass flow

40
Q

Which three gradients do dissolved sugars travel down in the phloem?

A

A hydrostatic pressure gradient, a concentration gradient, a pressure gradient

41
Q

What two things can the sugars be used for at sinks?

A

Respiration and storage

42
Q

Name the entire process by which dissolved sugars move from sources to sinks

A

Mass flow

43
Q

How can a potometer be used to measure the rate of water uptake?

A

As water is taken up into the plant, the bubble in the capillary tube moves. We can measure the distance travelled by the bubble in a time.

44
Q

Potometers can be used to measure the effect of variables on the rate of water uptake. Name these factors.

A

Light intensity, temperature, humidity.

45
Q

If the IV was light intensity, name the CVs.

A

Temperature, humidity, same plant.

46
Q

If the IV was temperature, name the CVs.

A

Light intensity, humidity, same plant.

47
Q

If the IV was humidity, name the CVs.

A

Temperature, light intensity, same plant.

48
Q

Why does using the same plant help make the results reliable?

A

Because the leaves will have the same surface area.

49
Q

Why might the rate of water uptake into a plant not be the same as the rate of transpiration?

A

Because water can be used for turgidity, in photosynthesis, and produced in respiration

50
Q

Which is faster - the speed of water movement through the capillary tube, or the speed of water movement through the plant roots?

A

Through the plant roots is faster

51
Q

Why is the speed of the water movement through plant roots faster in the roots of the plant compared to the potometer?

A

Because the roots have a smaller diamater

52
Q

Name five precautionary measures taken when setting up the potometer

A

Cut the shoots and insert the plant into the potometer underwater, dry the leaf, seal the joints with vaseline, and shut the tap

53
Q

Why should you cut the shoots and insert the plant into the potometer underwater?

A

To prevent bubbles entering the xylem

54
Q

Why should you dry the leaves?

A

Excess water on the leaves would lower the rate of transpiration

55
Q

Why should you seal the joints with vaseline?

A

To prevent bubbles entering the capillary tube

56
Q

Why should you shut the tap?

A

To ensure water isn’t introduced into the capillary tube from the reservoir

57
Q

How would you return the bubble to zero to carry out repeats?

A

By opening the tap to introduce water from the reservoir

58
Q

How would you calculate the distance the bubble travelled during the allocated time?

A

Final length - Initial length

59
Q

How would you calculate the volume of water taken up?

A

πr2h

60
Q

How would you calculate rate of water uptake?

A

volume of water uptake ÷ time

61
Q

How would you calculate the surface area of a leaf?

A

Draw around the leaf onto graph paper. Count the whole and half squares. X2 for both sides.

62
Q

How would you calculate rate of water uptake per surface area?

A

Rate of water uptake ÷ surface area

63
Q

What is a xerophyte?

A

A species of plant that has adaptations tosurvive in an environment with little liquid water, e.g. cactus.

64
Q

Describe five adaptations of xerophytes

A

Sunken stomata
Hairy leaves / hairy stomata
Thick waxy cuticle
Curled leaves
Spines instead of leaves

65
Q

Explain how sunken stomata reduces water loss

A

Water vapour is trapped around the stomata, reducing the water potential gradient

66
Q

Explain how hairy leaves / hairy stomata reduce water loss

A

The hairs trap water vapour around the leaves / stomata, reducing the water potential gradient

67
Q

Explain how a thick waxy cuticle reduces water loss

A

It reduces evaporation

68
Q

Explain how curled leaves reduces water loss

A

It traps water vapour around the leaf, which reduces the water potential gradient

69
Q

Explain how having spines instead of leaves reduces the water loss

A

They reduce the surface area to volume ratio

Biology (26 decks)

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