GFPIII operation manual
Opti-Sciences, Inc.
Measurement overview:
This technology shows a strong linear correlation to chemical chlorophyll content tests between
41 mg m
-2
and 675 mg m
-2
. It is ideal for precise measurements of chlorophyll content in this range.
Direct read out of Chlorophyll content in mg m
-2
is possible using the Gitelson equation included on the
instrument or the fluorescence ratio F735/F700 can be used .
Today, chlorophyll content is usually measured by destructive chemical methods or estimated by
nondestructive absorption techniques. While time and time again absorption instruments have been
proven to work well as a non-destructive test on many types of samples, they do have some limitations.
Absorption instrument limitations:
•
They require full coverage of the instrument measuring aperture by a leaf without holes,
•
They must be thin enough to allow transmission of red and infrared light,
•
The surface must be relatively flat and uniform
•
Variable fluorescence (or the Kautsky effect) caused by the red wavelength of absorption
instruments, limits the repeatability of measurements.
•
Selection of the measuring area, on smaller leaves, can cause measurement variations due to
leaf structure variation. Veins and midribs can cause significant variation.
•
The two wavelengths used in absorption methods, by the two major manufactures of this type of
instrument, limit linear correlation to chemical chlorophyll content methods
to values below 300 mg m
-2
.
As a result, absorption instruments do not work with conifer needles, turf grasses, Arabidopsis leaves,
moss, most CAM plants such as prickly pear cactus, and Agave, fruit, stems, petioles, lichens, and algae
on rocks. Furthermore, it is difficult to get reliable readings on very small leaf plants such as immature
rice and wheat.
For these reasons, Opti-Sciences decided that it was time to engineer an affordable solution for these
difficult applications. This section provides an overview of this technology.
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