Potometers

We use the EISCO potometer with a few adaptations:
1. permanently fix the clips with screws and glue (instead of the pathetic two sided tape)
This makes everything more robust
2. Remove the 5ml syringe and replace with a 100ml reservoir

This improves the machine by allowing you to feed the plant off the reservoir and I have set it up and left it all weekend - still works on the Monday morning (all be it a bit slower due to the stem getting blocked by infection).
3. Everything fixed on one clamp stand

Kit taped down, top clamp gently holding the plant second clamp holding the reservoir. The whole set up then can be easily transported to different locations.
Use the tap to control what you are doing . - in line for running, top and right to feed off reservoir, right and bottom to zero the capillary tube (using the liquid from the reservoir with care)

The good thing about the EISCO is you can remove the tube connector and fix it on the stem under water without any Vaseline or vacuum grease just cut it at an angle, push on to one end then seal with several twists of elastic band. Join up to machine under water. I use laurel because the stems are the right size are woody so they push into the tube easily and are evergreen so you do this at any time of year


 
Hi,

A teacher has asked me to set one up... I have never used one before and i dont know how it works, I have the same one as you. Please can you tell me what I do with it (new to this role) so i can explain to her what she needs to do. how far in advance do i need to set it up to do what it should do...whatever that is?? so confused. many thanks Allison.
 
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Peter Sigsworth

COMMITTEE
Hi,

A teacher has asked me to set one up... I have never used one before and i dont know hoe it works, I have the same one as you. Please can you tell me what I do with it (new to this role) so i can explain to her what she needs to do. how far in advance do i need to ste it up to do what it shoul...whatever that is?? so confused. many thanks Allison.
Have a go yourself first - follow my guide then ask me any questions about problems you came across. Start by cutting a branch of Laurel with a stem slightly wider than the tube. Take a flask of water with you so you can put the cut stem straight into the water (reduces any air bubbles in the xylem). When inserting the stem into the tube do it under water (in the sink) and cut off the first 3 cms or so before you insert (that should give you clean stem full of water and no air bubbles).
 
Have a go yourself first - follow my guide then ask me any questions about problems you came across. Start by cutting a branch of Laurel with a stem slightly wider than the tube. Take a flask of water with you so you can put the cut stem straight into the water (reduces any air bubbles in the xylem). When inserting the stem into the tube do it under water (in the sink) and cut off the first 3 cms or so before you insert (that should give you clean stem full of water and no air bubbles).
Ok thank you, does it have to be laurel or will a geranium work? what is supposed to happen?
 

Peter Sigsworth

COMMITTEE
Ok thank you, does it have to be laurel or will a geranium work? what is supposed to happen?
You can use geranium but you need a faily woody stem so you can make an air tight seal with the tube - Laurel grows all year round. Look at my setup and you'll see what laurel looks like - Privet should work also. The cut shoot will draw water from the apparatus as it losses it to the air through transpiration. The capillary tube has a small amount of food colouring in it so the student can see/measure the water being drawn up by the plant. Use the tap/valve to control where the plant draws the water from and also use it to zero the capillary tube for another run (att)
 

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  • potometer valve setting 1 .docx
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I do think teachers are a bit defeatist with this practical. I was called the other day, the usual, " Jaaaaaaaane, heeeeelp, it's not working"! cry.
It was.... :rolleyes:
Really not sure what they expect to see, I mean it's never going to be dramatic!
 

Peter Sigsworth

COMMITTEE
I do think teachers are a bit defeatist with this practical. I was called the other day, the usual, " Jaaaaaaaane, heeeeelp, it's not working"! cry.
It was.... :rolleyes:
Really not sure what they expect to see, I mean it's never going to be dramatic!
Here is an update on the Eisco potometer adaptation.
Set 5 up last week (day before) three classes used them all day with only one failure and that was because they left it running too long so air got into the stem attachment
Two attached files and a video I made (sorry about the background noise)
(47) EISCO potometer - YouTube
 

Attachments

  • Adapting and setting up an EISCO potometer.pdf
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  • potometer valve setting 1 .docx
    71.7 KB · Views: 7
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