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Biology Year 1 > 3.1.3- Transport in Plants > Flashcards

3.1.3- Transport in Plants Flashcards

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1
Q

why do plants require a transport system?

A

to ensure that all plant cells receive the sufficient amount of nutrients, amount is based on their SA:V ratio.

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2
Q

what 5 chemicals do plants need to transport and what are they used for?

A
  • CO2- reactant of photosynthesis
  • O2-product of photosynthesis, used in cellular respiration
  • organic nutrients- growth, survival + metabolic reactions
  • mineral ions + water- growth + survival
  • hormones- plant responses, growth of leaves/roots
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3
Q

what are the 3 reasons of why plants require a transport system?

A
  • metabolic demands, energy required for reactions/functions
  • size, large plants need to transport long way from roots to leaves
  • small SA:V ratio, transport system allows required substances to be transported and compensates for this
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4
Q

in plants, what is the role of the roots?

A

responsible for the uptake of water and mineral ions, through osmosis (passive process) and active transport (active process).

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5
Q

what is a HERBACEOUS DICOT plant?

A
  • make seeds that contain two cotyledons/seed leaves
  • leaves that have broad blades and petioles/stems
  • tap root with lateral branches, vein networks
  • herbaceous= soft tissue, short life cycle, non-woody tissue
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6
Q

what is the role of the xylem vessel?

A
  • transport of water/mineral ions from the roots to the rest of the plant
  • support
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7
Q

what is the structure of the xylem?

A
  • non-living tissue
  • long, hollow structures made by columns of cells that fuse together end to end
  • xylem fibres, long cells with lignified walls to provide extra mechanical support
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8
Q

what is the function of the phloem tube?

A
  • transports food in form of solute around the plant, from the source to the sink
  • applying the cells with sugars and amino acids
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9
Q

what is the structure of the phloem?

A
  • sieve tube elements
  • sieve plates with pores
  • tonoplast, vacuole membrane
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10
Q

what are the sieve tubes?

A
  • lined up end to end to within the phloem, used to transport sucrose
  • contain cross wall as intervals.
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11
Q

what are the companion cells

A
  • linked to the sieve tubes, in between them
  • carry out metabolic processes using ATP, due the many mitochondria
  • process is used load sucrose into sieve cells
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12
Q

what is TRANSPIRATION?

A

Water loss from plant leaves and stems via diffusion and evaporation.

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13
Q

what are the factors that affect transpiration?

A
  • number of leaves
  • number, size and position of stomata
  • presence of a cuticle
  • light
  • temperature
  • relative humidity
  • air movement/wind
  • water availability
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14
Q

how much of absorbed water evaporates out of the plant?

A

99%

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15
Q

what is the transpiration stream?

A

the movement of water from the roots to the leaves

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16
Q

how does air movement affect transpiration?

A
  • still air decreases rate of transpiration
  • still air= water molecules accumulate outside of leaf, creating a local area of high humidity, lowing conc gradient and the rate.
  • air currents increase rate of transpiration
  • air currents= sweep water molecules away from the leaf surface, which maintains conc gradient, increasing rate
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17
Q

how does temperature affect transpiration?

A
  • increased temp= increased kinetic energy, increasing the rate of transpiration, water is moving out of leaf
  • too high of temp= stomata closes to prevent excess water loss, reducing the rate of transpiration
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18
Q

how does humidity affect transpiration?

A
  • humidity=amount of water vapour in the air
  • high humidity means that there is a large conc of water molecules in the air surrounding leaf
  • high humidity= decreased rate of transpiration, due to the reduced water vapour conc gradient between in and out of leaf
  • certain level of humidity= equlibrium is reached, no net water loss of leaves
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19
Q

how does light/light intensity affect transpiration?

A
  • dark= stomata close, reducing rate of transpiration
  • sufficient light= stomata open, increasing rate of t
  • once stomata are open, light intensity has no effect on the rate
  • too much light, stomata will close to prevent too much water loss.
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20
Q

how does the number of leaves affect transpiration?

A
  • more leaves= bigger surface area

- bigger surface area= more stomata for gas exchange,resulting in more water loss through transpiration

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21
Q

how does number, size and position of stomata affect transpiration?

A
  • more stomata= more pores for transpiration, increasing the rate
  • sunken stomata= decreased rate, as the boundary layer increases
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22
Q

how does the presence of a cuticle affect transpiration?

A
  • thicker the cuticle, the slower the rate

- cuticles are water repellent so water cannot move through as quickly, hence the rate decreases

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23
Q

how does water availability affect transpiration?

A

-the more availabilty in the soil, the more transpiration will take place

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24
Q

what is the vascular system in dicot plants?

A

=a series of transport vessels running through stems, roots and leaves.

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25
Q

what are the 3 organs in a plant?

A
  • leaves
  • roots
  • stems
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26
Q

what is transpiration a consequence of?

A

a consequence of gaseous exchange

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27
Q

what are the 3 advantages of transpiration?

A
  • provides mean of cooling plant through evaporative cooling
  • transpiration stream helpful in nutrients uptake
  • turgor pressure of cells provides support to the leaves and the stem (providing an increased SA of leaf blade)
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28
Q

what causes the movement of water through the xylem?

A
  • evaporation of water vapour from the leaves

- cohesive and adhesive properties of water

29
Q

what is the driving force of water movement being permitted?

A
  • a gradient in water potential

- high water potential in soil, to low water potential in atmosphere, occurs through plant cells

30
Q

what is the rate of transpiration dependent on?

A

the concentration gradient of water vapour between the inside of the leaf and in the surrounding air.
-large conc gradient= faster transpiration rate.

31
Q

why must plants take up a constant supply of water/dissolved minerals?

A
  • to compensate for continuous loss of water

- so that they can photosynthesise + produce proteins.

32
Q

what is the name of the first pathway that water can take to cross the cortex, and give details on it?

A

APOPLASTIC PATHWAY-

  • water travels through spaces running through cellulose cell wall + hollow tubes of xylem
  • water moves by diffusion and can move directly from wall to wall/through intercellular spaces
  • water becomes blocked by the casparian strip, so water begins to take the symplastic route at this point
33
Q

what is the casparian strip?

A

the presence of a thick, waterproof, waxy band of suberin within the cell wall blocks the apoplastic pathway, within the endodermis part of plant.

34
Q

what is the name of the second pathway and give details?

A

SYMPLASTIC PATHWAY

  • little amount of water travels through cytoplasm/plasmodesmata/vacuale of cells
  • osmosis
35
Q

what does the casparian strip help the plant to do?

A

helps the plant to control which mineral ions, dissolved in the water, can move into the xylem vessel.

36
Q

what is the cohesion-tension theory?

A

the movement of water through a plants xylem is largely due to the evaporation of water vapour from the leaves and the cohesive and adhesive properties exhibited by water molecules

37
Q

describe the movement of water through the leaves, 4?

A
  • water vapour loss lowers water potential in air spaces around mesophyll cells.
  • this water evaporates into air spaces, resulting in transpirational pull
  • pull= water moves through mesophyll cell wall/out of cytoplasm
  • pull from water moving results in water leaving xylem vessel through pits, causing water to move up xylem, due to cohesion/adhesion.
38
Q

what is the source in translocation?

A

the regions of a plant where assimilates are produced

39
Q

what are some examples of sources?

A
  • leaves

- storage organs

40
Q

what is the sink in translocation?

A

the region of a plant where assimilates are stored/removed

41
Q

what are some examples of sinks?

A
  • roots
  • meristem
  • fruits
42
Q

what are xerophyte plants?

A

plants that have adapted to live in dry and arid conditions, so their adaptation are to maximise the water intake

43
Q

what are two examples of xerophytes?

A
  • cacti

- marram grass

44
Q

what are some adaptations of cacti and what do they do?

A
  • modified leaves to reduce transpiration, less SA
  • sunken stomata, located in pits to produce an environment of moist air, to reduce water vapour and transpiration
  • hairy leaves/spines
  • succulent, store water in parenchyma tissue in roots and stems, used in times of drought.
  • long tap roots, to gain water from deep down in ground
45
Q

what are some adaptations of marram grass and what do they do?

A
  • sunken stomata, reduces transpiration
  • hairy leaves, rolled leaves, reduce transpiration
  • hinge cells shrink when flaccid, producing humid place in rolled leaf, reduces diffusion of water
  • long vertical roots that penetrate sand, extensive network, enables sand to hold more water
  • stomata only in upper epidermis, open in humid space
46
Q

what are some other adaptations of xerophytes?

A
  • thick waxy cuticle
  • reduced number of stomata
  • reduced leaves
  • leaf loss
  • stomata opens and closes at day and night
47
Q

what are hydrophytes?

A

plants that have adapted to live in fresh water

-adapted to face main challenge of receiving enough CO2 during day and oxygen at night, as water contains less than air

48
Q

what is an example of a hydrophyte?

A

water lily

49
Q

what are the adaptations of water lillies, and what do they do?

A
  • stomata on upper surface of leaf to be near air, where they are open to maximise gaseous exchange
  • wide, flat leaves to gain as much light as possible
50
Q

what are other adaptations of hydrophytes?

A
  • thin waterproff waxy cuticle
  • reduced root system, small roots required, can extract nutrients through tissue
  • reduced veins in leaves, xylem reduced, no need to transport water around plant
  • air sacs help plant float on water
  • large SA of stems and roots to maximise photosynthesis
  • reduced structure
51
Q

what is aerenchyma

A

=specialised packing tissue with large air spaces

  • makes leaves and stem buoyant
  • forms a low-resistant internal pathway for movement of substances, helps plant cope with anoxic conditions
52
Q

what is translocation?

A

the transport of assimulates from source to sink via the phloem, requiring the input of metabolic energy/ATP

53
Q

what are assimulates?

A

substances that will become incorporated into biological tissue.

54
Q

what is an example of a source?

A

leaves, photosynthesis produces glucose which is transported as sucrose, as sucrose has less of an osmotic effect than glucose

55
Q

what are two examples of sinks?

A
  • roots, that are growing and / or actively absorbing mineral ions
  • meristems (apical or lateral) that are actively dividing
56
Q

what are two examples in the way that their has been understanding about translocation?

A
  • using radioactively labelled metabolites (eg. Carbon-14 labelled sugars) which can be traced during translocation
  • Collecting and studying the sap from plants with ‘clotting’ sap, eg- castor oil plants
57
Q

why are carbohydrates transported in plants as sucrose, give two reasons?

A
  • it allows for efficient energy transfer and increased energy storage, sucrose= dissacharide, so more energy
  • it is less reactive than glucose as it is a non-reducing sugar and therefore no intermediate reactions occur as it is being transported
58
Q

what are the steps to the active loading as part of translocation?

A
  • apoplastic pathway (through the cell walls) = active process
  • if the sucrose molecules are taking the apoplastic pathway then transfer cells (modified companion cells) pump hydrogen ions out of the cytoplasm via a proton pump and into their cell walls, requiring ATP
  • the large concentration of hydrogen ions in the cell wall results in the hydrogen ions moving down the concentration gradient back to the cytoplasm of the companion cell.
  • the hydrogen ions move through a cotransporter protein, transporting the hydrogen ions and carrying sucrose molecules into the companion cell against the concentration gradient for sucrose
  • the sucrose molecules then move into the sieve tubes via the plasmodesmata from the companion cells, which have infoldings in their cell surface membrane to increase the available surface area for the active transport of solutes and many mitochondria to provide the energy for the proton pump
59
Q

what does this active loading mechanism permit plants to build up, and how much?

A

permits some plants to build up the sucrose in the phloem to up to three times the concentration of that in the mesophyll

60
Q

what are the steps to the unloading/removal at the sink during translocation?

A

-sucrose actively transported out of the companion cells, then moved out of the phloem tissue via apoplastic or symplastic pathways

61
Q

how is the concentration gradient maintained in the sink tissue?

A

sucrose is converted into other molecules

62
Q

what are the two protein pumps called, which are involved with the loading of sucrose during translocation?

A
  • proton

- cotransporter

63
Q

what is the name of the apparatus used to estimate the transpiration rate of a leafy shoot?

A

potometer

64
Q

what does a potometer do?

A

A simple potometer is a piece of capillary tubing to which a plant has been connected.
The water uptake is measured by recording the time taken for a bubble in the tube to move a set distance.

65
Q

what is the function of a potometer?

A

A device used to measure the rate of water uptake of a plant, and hence the rate of transpiration.

66
Q

as part of the potometer experiment, why must the stem be cut underwater? and why must it be slanted?

A
  • to prevent air bubbles from forming in the vascular bundle

- to increase SA for maximum water uptake

67
Q

outline the procedure for the potometer experiment in 6 steps?

A
  • set up the potometer
  • clamp capillary tube into stand, with bottom of it being in the water
  • smear petroleum jelly around the join to maintain airtight conditions
  • leave for 5 mins for bubble to appear in capillary tube
  • measure the movement of the bubble along tube in certain amount of time
  • repeat and change abiotic variable each time
68
Q

how is rate of transpiration calculated using findings of potometer?

A

-distance bubble travelled and radius of tube
-volume of water using pi r squared
=volume / time

69
Q

what are the limitations of the potometer experiment?

A
  • not all water is transpired, some is used to maintain turgidity, and for photosynthesis
  • plant is dying when stem is cut, so rate of water uptake is therefore slower than normal.

Biology Year 1 (12 decks)

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