plant transport Flashcards

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1
Q

what do phloem vessels do?

A

transport food materials (mainly sucrose & amino acids) made by the plant from photosynthesising leaves to non-photosynthesising regions in the roots and stem
—> this means that movement can be in any direction around the plant

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2
Q

differences between xylem & phloem?

A

phloem:
- cells are living cells and not hollow
- substances move from cell to cell through pores in the end walls of each cell

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3
Q

information about the xylem?

A
  • roots, stem and leaves form plant organ system for transport of substances around the plant
  • plants also possess 2 specialist transport vessels called xylem and phloem
  • xylem and phloem arranged throughout the root, stem and leaves in groups called vascular bundles
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4
Q

structure and function of the xylem

A
  • xylem vessels transport water and minerals from roots to stem and leaves

key structural features:
- composed of dead cells which form hollow tubes
- xylem cells strengthened by lignin - so adapted for transport of water in transpiration stream

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5
Q

what are root hair cells for?

A

they’re adapted for the efficient uptake of water (by osmosis) and mineral ions (by active transport) into the roots

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6
Q

how are root hair cells adapted?

A
  • they’re single celled extensions of epidermis cells in the root
  • grow between soil particles and absorb water & minerals from soil
  • increase surface area to volume ratio significantly —> this increases the rate of the absorption of mineral ions by active transport
  • high proportion of dissolved minerals and sugars in cytoplasm (of root hair cell) give it low water potential (less watery) —> water moves into root hair cell by osmosis
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7
Q

what’s the stuff from the diagram of the xylem that i can’t put on here say??

A
  • no cell contents just a continuous column of water
  • original cell wall between cells has broken down
  • walls thickened with lignin
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8
Q

what are the organelles in root hair cells?

A
  • ribosomes
  • mitochondria
  • nucleus
  • cytoplasm
  • cell membrane
  • cell wall
  • root hair
  • vacuole
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9
Q

what’s the route of water through the plant?

A

the structure of a root specifically allows it to maximise absorption of water by osmosis and mineral ions by active transport

  • water moves, by osmosis, into root hair cells, through root cortex & into the xylem vessels:
  • once the water gets into the xylem, it’s carried up to leaves where it enters mesophyll cells in leaves

so pathway is:
root hair cell —> root cortex cells —> xylem —> leaf mesophyll cells

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10
Q

2.56B transpiration definition

A

the loss of water vapour from the parts of the plant that are above ground (leaves, stem, flowers)

(the evaporation of water from the surface of a plant)

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11
Q

how does transpiration work?

A
  • loss of water occurs through evaporation of water at surfaces of spongy mesophyll cells followed by diffusion of water vapour through the stomata
  • the many interconnecting air spaces between the mesophyll cells and the stomata creates a large surface area
  • this means evaporation can happen rapidly when stomata are open
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12
Q

the effect of transpiration

A
  • water moves through xylem vessels in a continuous transpiration stream from roots to leaves via the stem to replace the water that’s been lost due to transpiration
  • due to cohesion, water in xylem creates a continuous unbroken column (each individual molecule ‘pulls’ on the one below it)
  • transpiration produces tension or ‘pulls’ on water in xylem vessels
  • if rate of transpiration from leaves increases, water molecules pulled up the xylem vessels quicker
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13
Q

the function of transpiration

A
  • transporting mineral ions
  • providing water to keep cells turgid in order to support structure of plant
  • providing water to leaf cells for photosynthesis
  • keeping leaves cool, the conversion of water (liquid) into water vapour (gas) as it leaves the cells & enters airspace requires heat energy. use of heat to convert water into water vapour helps cool plant down
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14
Q

2.57B factors that affect rate of transpiration

A

air movement/wind speed, humidity, light intensity, temperature

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15
Q

2.57B how does air movement effect the rate of transpiration?

A

more transpiration:
- good airflow removes water vapour from air surrounding leaf
- sets up concentration gradient between leaf and air
- increasing water loss

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16
Q

2.57B how does humidity effect rate of transpiration?

A

less transpiration:
- humidity is measure of moisture (water vapour) in air
- when air saturated with water vapour concentration gradient is weaker
- so less water is lost

17
Q

2.57B how does light intensity effect the rate of transpiration?

A

more transpiration:
- guard cells responsive to light intensity
- when it’s high they’re turgid & stomata open allowing water to be lost

18
Q

2.57B how does temperature effect rate of transpiration?

A

more transpiration:
- at higher temperatures, particles have more kinetic energy
- so transpiration occurs at faster rate as water molecules evaporate from mesophyll and diffuse away faster than at lower temperatures

19
Q

what are the 2 types of potometer

A
  • mass potometer measures change in mass of a plant as a measure of amount of water that’s evaporated from leaves & stem
  • bubble potometer measures uptake of water by a stem as a measure of the amount of water that’s being lost by evaporation, consequently pulling water up through stem to replace it
20
Q

2.58B what apparatus do you need to investigate the effect of environmental conditions on transpiration?

A

apparatus:
- potometer (mass or bubble)
- timer
- lamp
- ruler
- plant

21
Q

2.58B what’s the method for investigating the effect of environmental conditions on transpiration (bubble potometer)?

A
  • cut a shoot underwater —> to prevent air entering xylem and place in tube
  • set up apparatus and make sure it’s airtight, use vaseline to seal gaps
  • dry leaves of shoot (wet leaves affect results)
  • remove capillary tube from beaker of water to allow single air bubble to form & place tube back into water
  • set up lamp 10cm from leaf
  • allow plant to adapt to new environment for 5 mins
  • record starting location of air bubble
  • leave for 30 mins
  • record end location of air bubble
  • change light intensity
  • reset bubble by opening tap below reservoir
  • repeat experiment
  • calculate rate of transpiration —> further bubble travels in same time period, greater the rate of transpiration
22
Q

what’s the equation for rate of transpiration?

A

rate of transpiration = distance moved by air bubble (m) / time (min)