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Green > 3.1.3: Transport in plants > Flashcards

3.1.3: Transport in plants Flashcards

1
Q

What are the 3 reasons for the need for transport systems in multicellular plants ?

A
  • Size
  • Metabolic rate
  • SA:VR
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2
Q

How does size mean a plant needs a transport system ?

A

Need to move substances from root to tip and from areas which photosynthesize to areas that don’t by also overcoming limitations of diffusion over large distances

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3
Q

How does metabolic rate mean a plant needs a transport system ?

A
  • Increases levels of activity compared to singlecellular so system needed to trans[port products of photosynthesis and remove waste products
  • Higher demand for O2 and nutrients
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4
Q

How does SA:VR mean a multicellular plants needs a transport system ?

A

Smaller SA:VR to take in whats needed for photosynthesis and respiration

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5
Q

What does dicot mean ?

A

2 leaves

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6
Q

What does monocot mean ?

A

1 leaf

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7
Q

Where are vascular systems found ?

A

Roots, stems and leaves of herbaceous dicotyledonous plants

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8
Q

What are the 3 components of vascular systems ?

A
  • Xylem
  • Sieve tube element
  • Companion cell
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9
Q

Give features of a xylem

A
  • Thick lignified and waterproof wall
  • No organelles
  • Continuous hollow tube
  • Made from dead elongated cells
  • Bordered pits are non lignified and allow water to pass into adjacent vessels
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10
Q

What is the function of the xylem ?

A

Transport water and mineral ions from the roots to the shoots and leaves

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11
Q

What 2 types of tissue are xylem made from ?

A

Xylem parenchyma - thick walled and pack around xylem to store food and contain tannin which is a bitter chemical to protect plant tissue from herbivore attack

Lignin - mechanical strength under transpiration pull to prevent collapse and waterproofing

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12
Q

Give features of a sieve tube element

A
  • Living cell
  • No nucleus
  • Few organelles
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13
Q

Give features of a phloem

A
  • Non lignified
  • Sieve tube
  • Sieve plates
  • Sieve tube element
  • Companion cell
  • Plasmodesmata
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14
Q

What is the function of a phloem ?

A

Transports assimilates such as sucrose and amino acids up and down the plant ( both directions)

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15
Q

What are sieve plates ?

A

Areas between cells where the walls become perforated

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16
Q

What are plasmodesmata ?

A

Gaps between sieve tube elements and companion cells

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17
Q

Why are there few organelles in phloem

A

As large pores appear in cells wall , the tonoplast, nucleus and organelles break down so phloem fills with sap

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18
Q

What is a feature of mature phloem ?

A

No nucleus

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19
Q

Give a feature of companion cells

A

Maintain their nucleus and organelles to provide ATP for active transport of organic substances

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20
Q

What are the 2 types of phloem supportive tissue ?

A
  • Parenchyma - contains fibres and schlereids with a thick cell wall for support
  • Sclerenchyma - mechanical strength and structrural support
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21
Q

Where is the position of vascular bundles in a stem ?

A

Around edge for structural support

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22
Q

What is the midrib in a leaf ?

A

The main vein carrying vascular tissue and supports leaf structure

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23
Q

Where is the position of vascular bundles in a root ?

A

In the middle to help plant withstand tugging strains resulting from stems and leaves blowing in wind

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24
Q

What is the cambium ?

A

Stem cells between the xylem and phloem

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25
Q

What does a potometer do ?

A

Measures transpiration rate by measuring water uptake

26
Q

What does a potometer assume ?

A

Water uptake = water loss by transpiration

27
Q

What is transpiration a consequence of ?

A

Gas exchange

28
Q

Define transpiration

A

The loss of water by evaporation from the leaves of a plant

29
Q

Give 5 steps that need to be carried out when setting up a potometer and why

A
  • Set up underwater ( no air is drawn up capillary tube)
  • Ensure shoot is healthy ( no damaged tissue that won’t respire)
  • Cut stem underwater ( constant transpiration stream isn’t disrupted and air isn’t sucked up the stem and trap and air bubble in xylem)
  • Dry leaves ( concentration gradient exists between leaves and outside environment)
  • Seal potometer with vaseline ( air tight so water can’t leak out and it is a closed system)
30
Q

Give the 5 factors that affect transpiration rate

A
  • Light
  • Humidity
  • Temperature
  • Air movement
  • Soil water availability
31
Q

How does light affect transpiration rate ?

A

In light, stomata open for gas exchange so by increasing light intensity, more stomata open which increases rate of evaporation and therefore transpiration

32
Q

How does soil water availability affect transpiration rate ?

A

If dry, plant is under water stress which decreases the rate of transpiration

33
Q

How does humidity affect transpiration rate ?

A

High humidity lowers rate of transpiration as there is a lower water potential gradient between inside leaf and outside air

34
Q

Define humidity

A

Measure of the amount of water vapour in air compared to total concentration of water air can hold

35
Q

How can temperature affect transpiration rate ?

A

An increased temperature increases kinetic energy of water molecules which increases evaporation rate from spongy mesophyll cells into air spaces of leaves which increases transpiration rate. Also increases the concentration of water vapour that the external air can hold which decreases the humidity and water potential of plant but increases rate of transpiration

36
Q

How does air movement affect rate of transpiration ?

A

More wind will increase the rate as less still air will be trapped by hairs and accumulate close to leaf. Water vapour potential around stomata won’t increase and diffusion gradient is maintained for transpiration

37
Q

How does water enter the roots of a plant ?

A

Diffuses by osmosis into root hair cell down a water potential gradient ( soil has a low concentration of dissolved minerals so has a high water potential)

38
Q

How does water cross the root to the xylem ?

A

Symplast or apoplast pathway

39
Q

Describe the symplast pathway

A

Water moves through the cytoplasm of root hair cells which are connected through plasmodesmata
- Water moves by osmosis as each successive cell has a lower water potential as water diffusing in from the soil dilutes the cytoplasm
- Steep water potential gradient maintained as when water leaves the root hair cell, the water potential of the cytoplasm falls

40
Q

Describe the apoplast pathway

A

Water moves through the space between open network of fibres in cell walls
- Due to cohesive forces between water molecules as hydrogen bonds form creating a continuous stream
- Transports faster than symplast as little resistance to water in the cell wall

41
Q

What happens part way through the apoplast pathway ?

A

It is blocked by the casparian strip which is made of waxy suberin. Water is forced into cytoplasm through cell surface membrane to join the symplast pathway

42
Q

Summarise how water moves up the xylem

A

By mass flow down a hydrostatic pressure gradient

43
Q

Describe cohesion/transpiration pull

A

Water molecules hydrogen bond with eachother meaning water forms a continuous

44
Q

Describe capillary action / adhesion

A

Water molecules form hydrogen bonds with carbohydrates in xylem vessels meaning they can rise up the stem against gravity to replace water lost by transpiration

45
Q

Describe cohesion tension theory

A

Transpiration pull and adhesion results in tension in the xylem which moves water across roots from soil

46
Q

Define transpiration pull

A

Water vapour moves into external air through stomata along diffusion gradient through the plant

47
Q

Describe root pressure

A

Active pumping of minerals into xylem produces movements to push water up xylem

48
Q

What are the 4 main mechanisms of movement of water through a plant

A
  • Cohesion
  • Adhesion
  • Cohesion tension theory
    -Root pressure
49
Q

Give 2 examples of xerophytes

A

Cacti ( reduced leaves)
Marram grass ( long vertical roots, sunken stomata, curled leaves)

50
Q

Give 3 adaptations of xerophytes

A
  • Reduced stomata
  • Thick waxy cuticle
  • Hairy leaves
51
Q

Give an example of a hydrophyte

A

Water lilies ( many open stomata on upper surface, wide and flat leaves)

52
Q

Give 3 adaptations of hydrophytes

A
  • Many open stomata on upper surface
  • Wide, flat leaves
  • Air sacs
53
Q

What are 3 normal adaptations of plants to limit water loss ?

A
  • Waxy cuticle
  • Stomata on underside of leaf
  • Roots that grow down towards soil
54
Q

What is translocation ?

A

An energy requiring process to transport assimilates such as sucrose in the phloem between sources such as leaves to sinks such as roots and the meristem

55
Q

What is the source of a plant ?

A

The part of the plant which releases sucrose into the phloem

56
Q

What is the sink of a plant ?

A

Part of the plant which removes sucrose from the phloem

57
Q

What is the casparian strip made from ?

A

Suberin

58
Q

State 2 differences between the STRUCTURE of xylem and phloem

A
  • Xylem contains lignin whereas phloem doesn’t
  • Phloem has companion cells whereas xylem does not
59
Q

Give 2 similarities between the STRUCTURE of the vascular tissues xylem and phloem

A
  • Both made up of cells joined end to end
  • Xylem vessels and phloem sieve tube elements both lack nuclei and organelles
60
Q

How is water moved up the xylem from roots to leaves?

A

-Moved via the transpiration stream as water is under tension and due to adhesive properties of xylem allowing capillary action against gravity
- Water moves up xylem by mass flow down hydrostatic pressure gradient

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