j.hoddinott at unsw.edu.au
Thu Jun 11 18:34:30 EST 1998
I did my PhD with Paul Gorham on phloem translocation and learned steam
girdling from him. The system you describe does work but the hose from the
boiling water flask in Paul's lab ended in a Pasteur pipette to direct the
steam. He wrapped string around the pipette to make it safe to hold.
I subsequently went on to do a post-doc with Carole Swanson and he had a
different approach. Carole had some bent wire attached to electrodes. With
a rheostat he could increase the voltage accross the wire until it started
to glow red. He then held the bent wire at the point on the stem or
petiole that needed girdling.
I thought both proceedures effective and inherently dangerous. When I set
up my own lab I used what I consider to be a superior method. Get a cheap,
basic, Radio Shack (Tandy) soldering iron. Bend the tip into a C-shape.
Place the plant part in the 'C' of the hot soldering iron for as long as
necessary. I found 30 s a side quite adequate. You can clamp the
soldering iron and simply twist the plant around if the plant is not too
large. There was no major loss of turgor during the process but support is
needed very soon afterwards.
>Has anyone had experience with steam girdling to kill phloem without
>mechanically injuring a plant stem? I'm working on a high school biology
>text and would like to include an activity to stress the difference
>between transport in dead xylem vesels and live phloem.
>I'm picturing a 250 mL flask of boiling water with a one-hole stopper
>and a piece of wide rubber tubing slit lengthwise near the end to insert
>the stem and close with a pinchcock or screwcock clamp. But will this
>work? Will the steam cool and condense too much before reaching the
>stem? Or will it jet out and scald the kids? Any thoughts or hints for
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