nofishing
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#1
Report Thread starter 11 years ago
#1
Hi, I have done a couple of past papers at school which have had questions about the different precautions you need to take when using a potometer in order to get an accurate reading, and I have managed to lose my notes which told me which precautions to take, for example
  • cut shoot at an angle
  • dry the leaves
  • cut shoot underwater
  • etc


but i was wondering if anyone had like a definitive list of the precautions you take, this is OCR AS Biology btw.

Cheers
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LearningMath
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#2
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I'd like to know as well
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nofishing
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#3
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Not really sure if this is the right forum so feel free to move if appropriate
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Tinkerbelle ♥
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Also set the apparatus up under water in a bowl or something to prevent any air bubbles.

When placing the shoot in the potometer make sure you get an air tight seal otherwise it won't work using either a rubber bung or vaseline.

Ensure water resevoir is filled up so you can start again if necessary allowing you to make it a fair test as you won't need to set all the apparatus up again to be able to re-fill the potometer with water
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nofishing
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1 cut (healthy) shoot under water (to stop air entering xylem vessels);
2 cut shoot at a slant (to increase surface area);
3 check apparatus is full of water / is air bubble free / no air locks;
4 insert shoot into apparatus under water / AW;
5 remove potometer from water and ensure , airtight / watertight,
joints around shoot;
6 dry leaves / AW; max 4
7 keep , condition(s) / named condition(s) , constant;
8 allow time for shoot to acclimatise / AW;
9 shut screw clip;
10 keep ruler fixed and record position of air bubble on scale;
R ‘move bubble to end’ ideas
11 start timing and, measure / calculate, distance moved per unit time
/ AW;
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123jess
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#6
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does anybody know why you have to cut the shoot at a slant?
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han28
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#7
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(Original post by 123jess)
does anybody know why you have to cut the shoot at a slant?
you cut it at a slant to increase the surface area for where the water will enter the shoot via osmosis
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swimming1
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#8
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Why do you have to dry the leaves??
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DON pablo11
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#9
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leaves need to be kept dry to prevent water from obstructing the stomata as in wet leaves the water potential gradient between the inside and outside will be reduced so the rate of transpiration will be reduced.
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sonny.jim
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#10
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Why does the shoot need to acclimatise?
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