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A Level Biology OCR > Ch9 Transport in Plants > Flashcards

Ch9 Transport in Plants Flashcards

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1
Q

What are 3 plant processes that occur?

A
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2
Q

What are the 2 transport systems in plants?

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3
Q

How are root hair cells adapted to do their job?

A
  • RHC have specialised exchange surfaces for uptake of H2O and Mineral Ions
  • RHC are approx 200-250 micrometres, visible to naked eye
  • Thousands of RHC on each root- maximise S.A. in contact with soil for optimal uptake.
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4
Q

How do root hair cells absorb water by osmosis?

A
  • When RHC contact soil, water moves in via osmosis
  • Permeable cellulose cell wall
  • PPM (partially permeable membrane)
  • In vacuole of RHC, cell sap contains solutes
  • Osmosis occurs because there is higher concn of solutes in plant than soil
  • Thus creates favourable water potential gradient
  • Lower Ψ in RHC, higher Ψ in soil.
  • Steeper the concn gradient, the quicker the net movement of water molecules = better uptake.
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5
Q

Draw and label the transverse section of the root:

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6
Q

What are the three pathways that water takes to travel in plants?

A

Apoplastic pathway, symplastic pathway, vacuolar pathway

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7
Q

Describe the Apoplastic pathway:

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8
Q

Describe the Symplastic Pathway:

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9
Q

Describe the Vacuolar Pathway:

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10
Q

What is the Casparian Strip and how does water travel through it in a plant?

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11
Q

What is the evidence for Active Transport in Root Pressure?

A
  • Affect of cyanide- cyanide stops mitochondria from working, Root Pressure decreases
  • Affect of temp- root pressure increases as temp increases, and vice versa. Suggests presence of enzyme controlled chemical reaction.
  • Reactant Availability- if O2 level or respiratory substrate level drops, root pressure decreases
  • Guttation- sap + water will move out of cut stems, suggests they are actively pumped out + not drawn up by transpiration.
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12
Q

What structures are involved in transport up the stem, and what directions do they transport in?

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13
Q

What does the Vascular Bundle look like in leaves?

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14
Q

What does Vascular Bundle look like in the stem?

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15
Q

What does Vascular Bundle look like in the root?

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16
Q

What is the structure of Xylem Vessel:

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17
Q

What is structure of Phloem Vessel?

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18
Q

What is transpiration?

A

Transpiration is the evaporation of water from a plants surface- mostly by leaves.

It is the loss of water vapour by evaporation through stomata.

19
Q

What pulls water up the plant?

A
  • Water vapour diffuses from leaves
  • Decreases Ψ of air space inside spongy mesophyll cell.
  • Water moves into air spaces from adjacent cells
  • Water moves out of xylem into cells in leaves
  • Water H-bonds to itself (cohesion)
  • and bond to walls of xylem vessel (tension)
  • resulting in capillary action.
20
Q

What properties of water lead to cohesion, adhesion and capillary action. Describe what each of these mean:

A
21
Q

How do the stomata open and close?

A
22
Q

Describe Capillary Action, a theory of how water travels from root to leaves:

A
23
Q

Describe Root Pressure, a theory of how water travels in a plant:

A
24
Q

Describe Cohesion Tension Theory:

A
25
Q

What is the evidence for Cohesion Tension Theory?

A
26
Q

What Factors affect transpiration and how?

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27
Q

What does a potometer measure?

A

Rate of water uptake of plant

28
Q

How is rate of water uptake calculated using a potometer?

A

volume of water taken up (dont forget πr2h )/ time taken for bubble to move.

29
Q

What are the limitations of the potometer experiment? How to improve?

A
  • not same process- plant draw up water with roots (not representative data)
  • not all water taken up is used for transpiration- some used for photosynthesis and maintaining turgidity
  • potometer only measures rate of water uptake
  • roots have a larger SA than a cut stem
  • no of leaves on shoot maybe not resemble normal plant
  • leaves may not be dried fully
  • whole plant will have a larger water demand- not the same thing!!

THEREFORE- value detained not representative of how real plants function. e.g. wet leaves reduce diffusion gradient so transpiration decreases.

How to improve limitations?

  • standardised test - maintain light intensity, keep conditions constant
  • use healthy shoot
  • cut shoot at a slant (larger SA)
  • use dried leaves
  • acclimatise plant
  • if shoot originally in sunny area, set up potometer in dark area, most stomata still going to be open if set up potometer too quickly
    • let plant adjust to change in environment = make results more specific to conditions of potometer.
30
Q

What is translocation?

A

translocation is the movement of assimilates from sources to sinks. From high conc to low conc.

31
Q

What is a source Vs what is a sink?

A
32
Q

According to Mass Flow Hypothesis, what occurs during mass flow in the phloem ( the SOURCE)

A
33
Q

According to Mass Flow Hypothesis, what occurs during mass flow down the phloem to the SINK and what does this result in?

A
34
Q

Given the nature of sinks, large proportion of sucrose is immediately used in respiration. What happens to the sucrose to prevent this?

A

Sucrose which is left is converted to starch (insoluble) and does not effect sucrose concn/water potential.

35
Q

Describe the process of Active Loading:

A
36
Q

What evidence is there for mass flow?

A
  • Advances in microscopy allow us to see adaptations of companion cells for AT.
  • If mitochondria of companion cell poisoned, translocation stops.
  • Ringing tree causes sugars to collect above ring.
  • An aphid feeds from the phloem using ‘stylet’. Stylet penetrates sieve tube and takes in sugars from phloem.
37
Q

Look at this diagram of the phloem:

A
38
Q

What are mesophytes?

A

Mesophytes are able to take up sufficient water to replace transpiration- includes most plants.

39
Q

What are Hydrophytes?

A

Hydrophytes live either partially or fully submerged in water, therefore have problems with oxygen uptake, water logging (no air spaces in plant).

40
Q

What are Xerophytes?

A

Xerophytes live in areas where water is lost via transpiration is greater than water taken up by roots. They have structural and physiological adaptations enabling them to survive in hot and dry conditions (equally in very cold or icy conditions).

41
Q

What are some adaptations (generally) of plants than limit h2o loss?

A
  • Waxy cuticle
  • stomata on underside of leaf
  • stomata closed at night
  • deciduous plants lose leaves in winter
  • roots that grow down to water in soil.
42
Q

What are some xerophyte adaptations?

A

Xerophyte adaptations, e,g, marram grass, cacti

  1. Thick, waxy cuticle - prevent water loss via cuticle
  2. Sunken Stomata- stomata located in pit, reduced air movement (provides still + humid microclimate)
  3. Less stomata- water loss reduced via transp
  4. Less Leaves (smaller SA)
  5. Hairy Leaves- still + humid microclimate
  6. Succulents (water stores)

A Level Biology OCR (23 decks)

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