WP4C 6 SAMPLE PREPARATION
6.5 Measuring Plant Samples
The WP4C can be used to measure the water potential of leaves
and plant material. Please refer to the application note: Measure-
ment of Leaf Water Potential Using the WP4, which can be found
at www.metergroup.com.
6.6 Taking a Reading
Once you have prepared your sample, you are ready to take readings.
Follow steps 1 through 5 to take readings.
1. Turn the sample drawer knob to the OPEN/LOAD position
and pull the drawer open.
2. Place your prepared sample in the drawer. Check the top lip
of the cup to make sure it is free from sample residue (remem-
ber, an over-filled sample cup will contaminate the chamber
sensors).
3. Carefully slide the drawer closed, being especially careful if you
have a liquid sample that may splash or spill and contaminate
the chamber.
4. Access the sample temperature menu (press lower right button)
to watch the temperature difference between the sample and
the instrument.
5. Turn the sample drawer knob to the READ position to seal the
sample cup with the chamber. The instrument will beep once,
and the green light will flash once to indicate that the reading
cycle has started. In about 40 seconds, the first measurement
will be displayed.
6.7 How WP4C takes Readings
The WP4C cooled mirror is controlled at the chamber dew point
and its temperature is measured.. When the instrument has finished
its read cycle, the water potential is displayed, accompanied by the
LED flash and beeper (if you have the beeper enabled).
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