Delta-T Devices AP4, User Manual

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Introduction
Page 6
Introduction
The AP4 cycling porometer is used for measuring the stomatal resistance of plant
leaves. This is a measure of the resistance to loss of water vapour through the stomata
and is an indicator of the physiological state of the plant. Stomata are sensitive to light,
carbon dioxide, pollutants, water stress and pathogens.
The AP4 provides an important tool for unravelling and understanding the intricate
web of mechanisms that control stomatal behaviour. It is also used to compare the
performance of different varieties and breeds of crops in phenotyping trials and in
response to environmental variation and stresses.
It measures how long it takes for a leaf to release enough water vapour to change
the relative humidity in a small chamber by a fixed amount. This is compared with a
calibration plate of known resistance to derive the stomatal resistance or conductance.
The method is well established. It is supported by a good theoretical understanding of a
cycling porometer (Monteith, Campbell & Potter, 1988), backed up by our considerable
manufacturing experience of this type of instrument, and has been in world-wide use
for over thirty years.
The AP4 corrects for changes in temperature. Readings are automatically converted into
units of resistance or conductance, and can be annotated, displayed, saved and
output to a computer or printer. Menu driven software, a 40 character by 8-line liquid
crystal display and dedicated function buttons make the use of the instrument as
intuitive and simple as possible.
A single button on the porometer head permits one-handed use. Consecutive readings
can be taken, evaluated and stored just by pressing this button. Stable readings are
denoted by the sound of a double "beep". Two porometer cup shapes are provided for
different leaf shapes. The head and case are relatively light, and a padded shoulder bag
with a waist-strap is provided.
Beginners can be up and running quickly and experienced users have easy access to the
default settings via the use of a context sensitive SET button. A HELP button displays
context-sensitive help messages.
A Quick Guide is provided.
See the video at
https://youtu.be/kA7yS8JJsLE
Download the AP4 Technical Manual from www.delta-t.co.uk