pressure bomb

This video is a visual 10 step instruction manual how to use a pressure bomb for measuring water pressure in the xylem of transpiring leaves. It is an entry for the www.ChloroFilms.org video competition.
Water in the xylem is under negative pressure. This tension can be measured by a pressure bomb. Tension pressure in a non-transpiring leaf is equivalent to water potential of cells surrounding the xylem (mesophyll cells), because the xylems osmotic potential is negligible.
A single leaf is sealed in the pressure chamber with the cut surface protruding through a rubber stopper. Pressure is applied to the shoot from a tank of compressed air (or nitrogen) until xylem sap appears at the cut ends of the xylem. The hydrostatic pressure inside the xylem elements is then identical to the applied external pressure. The amount of pressure that must be applied to force water out of the leaf cells into the xylem is regarded as equal to the xylem tension when the leaf was cut from the plant.

Category:

Education

Tags:

• ChloroFilms
• Plant physiology
• water pressure
• xylem
• leaf
• osmosis
• draught
• hydrostatic
• transpiration

[singingwaterboy]

NICE! much better than the ones we have at uni where you have to pump them for ages. But you should have put the leaves in a silver bad as soon as they came off the tree to stop them photosynthesising.

[Macwillacko]

idg

[monkeyfarman]

wtf?