[Plant-education] Re: Pressure Bomb Lab

David R. Hershey via plant-ed%40net.bio.net (by dh321 At excite.com)
Fri Jan 19 18:43:06 EST 2007


For a pressure bomb lab, Ross (1974) and Reiss (1994) recommended
comparing well-watered with water-deprived plants. Reiss (1994)
recommended using Xanthium strumarium leaves. Perhaps the students
could be asked to use the pressure bomb to determine which of two
groups of plants need irrigation. Some commercial growers use pressure
bombs to determine when irrigation is required (Reiter 2004, Sanden
Undated).

As a prelude to a pressure bomb experiment, Ross (1974) placed a shoot
horizontally in a solution of methylene blue or safranin and cut it
while the stem was submerged in the dye solution. Students sectioned
the stem into 0.5 cm sections above and below the cut to determine how
far the dye was drawn into the stem. Consumers are told to recut the
stems of cut flowers under water to remove air embolisms, which slow
water uptake by the stems. There are even special underwater flower
cutters sold to recut flower stems under water.

Here's a novel use for a pressure bomb that makes a dramatic
demonstration:

1. Place the cut end of each of two wilted herbaceous shoot cuttings in
separate small beakers of water.
2. Keep one cutting and beaker as the control.
3. Place the other cutting and beaker inside the pressure bomb (not the
usual way the pressure bomb is used).
4. Pressurize briefly, then release the pressure and remove the cutting
and beaker.
5. Ask students to explain why the cutting in the pressure bomb was
instantly "unwilted."


David R. Hershey


References

Reiss, C. 1994. Experiments in Plant Physiology. Englewood Cliffs, NJ:
Prentice Hall.

Reiter, C. 2004. Growers get help of 'bomb' Merced Sun-Star April 4.
http://www.agresearch.nu/merceed_april_04.htm

Ross, C.W. 1974. Plant Physiology Laboratory Manual. Belmont, CA:
Wadsworth.

Sanden, B. Undated. Bomb your cotton for maximum profit!! University of
California Cooperative Extension
http://pmsinstrument.com/sanden.htm



Sustainable Rider wrote:
> At the last minute, I'm trying to devise a lab that allows students to
> use a pressure bomb to ask an interesting plant water potential question
> (this is my intro botany class I can't stop fiddling with).  I've got
> two pressure bombs and have to run this lab in late February.  I usually
> do this outdoors in a fall ecology class but that's not really an
> option  at this point. Anyone have any tried and trues they'd care to share?
> 
> Laura Hyatt
> Rider University



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