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Biology Module 3 > 3.3 Transport in Plants > Flashcards

3.3 Transport in Plants Flashcards

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1
Q

why is transport systems needed in plants?

A

Meet high metabolic demand

Ensure nutrients reach all tissue

Overcome small surface area to volume ratio

Allow diffusion across large distances

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2
Q

what are the vascular tissues made up of

A

xylem and phloem

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3
Q

the xylem and phloem are situated in the vascular bundles. What are the 2 bundles called?

A

collenchyma and sclerenchyma

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4
Q

what is a dicotyledonous plant

A

have 2 seed leaves

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5
Q

describe how to dissect a plant to view the distribution of vascular bundles

A

staining, thin slice
view under microscope

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6
Q

explain mass flow hypothesis

A

the movement of water and solutes from an area of high concentration to an area of low concentration due to turgor pressure

due to hydrostatic pressure

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7
Q

describe translocation (6 marks)

A
  1. loading of sucrose into the top of the phloem from the SOURCE
  2. creates a high hydrostatic pressure at the top and a low water potential
  3. water moves in from the xylem by osmosis because of the low water potential
  4. the bottom of the phloem has a low hydrostatic pressure, so creates a hydrostatic pressure gradient
  5. the assimilates move down through the sieve plates
  6. water leaves the bottom of the phloem by osmosis, and is pulled back up to the top of the xylem because of transpiration
  7. assimilates loaded to the SINK
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8
Q

what are the features of the xylem?

A

Dead cells

No cell contents e.g. cytoplasm/nucleus

Lignified

No end walls - continuous flow of H2O

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9
Q

describe the active loading of sucrose from companion cell to sieve tube elements (6marks)

A
  1. H+ is pumped out of companion cell in proton pumps, by active transport
  2. Concentration of H+ outside is higher than inside so H+ moves back in, WITH sucrose, via a co-transporter protein
  3. the concentration of sucrose inside companion cells is higher than the concentration of sucrose in sieve tube elements so diffuse into sieve tube element down a conc. gradient, through PLASMODESMATA
  4. water moves in as well by osmosis generating a turgid pressure for MASS FLOW
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10
Q

what are the features of the phloem?

A

Tube of living elongated cells,

Pores in end walls so assimilates can move through

contain sieve plates, sieve tube elements and companion cells

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11
Q

describe how water enters through the root hair cells

A

The soil has a high water potential and root have a low water potential

Creates a water potential gradient that moves water from the soil to the root hair cells via osmosis

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12
Q

what happens when you remove a ring of material from the outer layer of a tree? Give reasons. 4 marks

A

The area above the missing ring begins to swell.
removes phloem - tree starts to die

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13
Q

describe the apoplast pathway

A

Goes through the cell walls and spaces between them

passive diffusion

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14
Q

describe the symplast pathway

A

Goes through the cytoplasm and plasmodesmata

Water moves through via osmosis

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15
Q

What does the Casparian strip do?

A

Blocks the apoplast pathway, forcing water into the symplast pathway

Symplast pathway is partially permeable, controls what substance can enter and get to the xylem

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16
Q

what is transpiration

A

the process by which plants release water vapour into the atmosphere through their leaves,

17
Q

How is water transported in the xylem ?
(6 marks)

A
  1. TRANSPIRATION
    Water evaporates from the leaves through the mesophyll cells, which creates a negative pressure or tension in the xylem.
  2. COHESION_TENSION THEORY
    Water molecules stick together due to hydrogen bonding, which creates tension.
  3. OSMOSIS
    The tension pulls water up through the xylem, creating an uninterrupted column of water.
  4. WATER MOVEMENT
    The water column moves up the xylem until it evaporates from the leaf’s walls.
18
Q

what is root pressure ?

A

Osmotic pressure in roots, cause sap to rise through stem of leaves

19
Q

what is the cohesion-tension theory? (4 marks)

A
  • COHESION - water molecules stick together because of hydrogen bonding
  • this creates TENSION which pulls the water up the xylem column creating a continuous flow of water
20
Q

what are the main factors affecting transpiration?

A
  1. Light intensity
  2. Temperature
  3. Humidity
  4. Wind
  5. Number of leaves
  6. Waxy cuticle presence
  7. Water availability
21
Q

how does temperature effect transpiration rate ?

A

Plants transpire more rapidly at higher temperatures because water evaporates more rapidly as the temperature rises.

22
Q

how does light intensity effect transpiration rate ?

A

causes more stomata to open, which allows water vapor to escape

rate of transpiration increases

23
Q

how does wind effect transpiration rate ?

A

faster wind = increased rate of transpiration

24
Q

how does humidity effect transpiration rate ?

A

Concentration gradient decreased

More H2O molecules in air than leaves

Rate of transpiration decreases

25
Q

What are xerophytes?

A

plants that are adapted to live in very dry conditions

26
Q

What are some adaptions of xerophytes?

A

Smaller leaves – reduces surface area

Densely packed mesophyll – prevents water loss via evaporation

Thick, waxy cuticles

Close stomata – in response to low water availability

Hair and pits – reduces water vapour potential gradient by trapping moist air

Deep roots or wide-spreading shallow roots

27
Q

what are hydrophytes?

A

Hydrophytes are plants which can live in water

28
Q

what are some adaptations of hydrophtes?

A

Thin or absent waxy cuticle – no need for conserving water supplies

Lots of stomata open constantly – maximises gas exchange by being placed on the upper surfaces

Flat and wide leaves – gives larger surface area to increase light absorption

Air sacs (found in some) – aids in flotation

29
Q

what is a potometer?

A

measures the rate of transpiration by measuring the water uptake of a plant.

30
Q

describe the process of using a potometer

A
  1. cut shoot
  2. insert shoot
  3. check for gaps
  4. dry leaves
  5. test for air bubbles
  6. note readings
  7. record using stopwatch
  8. calculate rate of transpiration
31
Q

when bark is removed from a tree, phloem is also removed, and the tree trunk above the cut starts to sell. Why?

A

assimilates cant move down past the cut

decreases water potential

causes an infection

Biology Module 3 (3 decks)

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