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[Plant-biology] how to remove the sap from a plant and then measure the sugar content

Tony Travis ajt at rri.sari.ac.uk
Fri Oct 14 07:10:25 EST 2005

> I am a high school student doing a science project on plant sap
> production. I need to grow a plant, remove the sap and then measure the
> sugar content.  Does anyone have a suggestion on how to remove the sap
> and then measure the sugar content.  

Hello, Jen.

One way to do this on a living plant is to use an aphid. These insects 
puncture stems with their mouth-parts and find the phloem: Then, you cut 
the aphid's body off its head, leaving the mouth-parts still in the 
phloem of the plant stem.

I know - it sounds gruesome...

Drops of the solution from the phloem can be collected from the aphid 
'head' with a pipette. This also happens from the holes left in stems 
and leaves when aphids feed naturally, and it makes them sticky.

The technique is called Aphid 'stylectomy':


Another possibility is to make very fine micro-pipettes by heating glass 
tubing in a Bunsen burner flame and then pulling it apart very quickly 
when it starts to melt (BE CAREFUL! and DON'T try this without proper 
supervision). You then have to do what the aphid does, but make sure 
nobody tries to use the aphid trick on you once you find the phloem...

This is MUCH harder than it sounds, because you really need to use a 
micro-manipulator to insert a glass micro-pipette into the phloem.

There are commercially available micro-pipette 'pullers':


Good luck!

Dr. A.J.Travis,                     |  mailto:ajt at rri.sari.ac.uk
Rowett Research Institute,          |    http://www.rri.sari.ac.uk/~ajt
Greenburn Road, Bucksburn,          |   phone:+44 (0)1224 712751
Aberdeen AB21 9SB, Scotland, UK.    |     fax:+44 (0)1224 716687

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