comparison of photosynthesis measurement systems (LCPro, LI-6400, CIRAS-2)

Uwe Grüters Uwe1.Grueters at t-online.de
Wed Aug 14 15:31:00 EST 2002


Dear colleagues,

for a research proposal I have to make a decision among the latest
commercially available photosynthesis measurement systems.

I intend to do A/Ci-curve at various temperatures and light response curve
measurements on various species from European extensively-managed grassland
(grass and herbaceous species). I aim to parameterize the Farquhar model for
the species under study.This sets the following requirements to the
measurement system: portable, controlled cuvette microclimate with regard to
temperature and VPD, light dosing unit, CO2 supply unit.

I do have several months of experience with A/Ci-curve measurements using
the LI-6400 (LI-COR BioSciences). However, it took us considerable time to
get reliable A/Ci-curves with the LI-6400. We got very competent assistance
from LI-COR with regard to technical problems during that time. Anyhow, we
always favored manual operation of the measurement system over the automatic
operation. Finally, we received a body of reliable and satisfying curves.

However, recently two new systems comparable to the LI-6400 have entered the
market, namely the LCPro (ADC BioScientific) and the CIRAS-2 (PP Systems). I
did an intensive search on the web for a comparison or test of these newly
developed systems, but I was not successful in doing this.

The prices, actually, are quite different, ranging from about ? 20.000,- for
the LCPro to ca. ? 25.000,- for the CIRAS-2 and ca. ? 40.000,- for the
LI-6400, respectively. This suggests, that the LI-COR is the most
sophisticated system.

I compared the technical specifications of the systems.

Unfortunately, so far ADC does provide merely a preliminary specification
for the LCPro. From the data sheet it appears to me that the accuracy of the
H2O-signal is an order of magnitude less than for the other systems. This
might be critical, when taking into account, that calculation of Ci-values
is based and crucially dependent on accurate transpiration measurement.
Further, ADC does not use the IRGA-technique for the H2O-measurement.
Instead, it uses laser-trimmed fast response water vapour sensors (? a not
very concrete information). The preliminary data sheet lacks information
about response times of the system as well. This might play a pivotal role
in regulating the cuvette microclimate.

>From the specificaition of the CIRAS-2 I had difficulties to find out if the
IRGA technique used by the CIRAS is similar to that of the LI-6400. (The
LI-6400 sensor head has two complete, dual path, non-dispersive infrared
analyzers, which both measure absolute concentrations of CO2 and H2O of both
reference and sample cell. However, the CO2/H2O accuracy of the CIRAS seems
slightly better and the response time worse than that of the LI-6400,
respectively. The IRGA seems not to be located in the chamber head. Thus,
this might give rise to the slower response time of the CIRAS.

This is what I found out so far.

Does anyone know of additional technical differences among the systems in
question? Are my interpretations of the dissimilarities correct so far? Are
there any experimental studies in the scientific literature, that compare
these photosysnthesis systems? Are there any tests out concerning the
performance of the measurement systems? Does anybody have experience doing
A/CI-curves with two or more of the systems?

Any comments to the issue would be of great help to me.
Thank you very much in advance, Uwe Grüters

. Dr. rer. nat. Uwe Grters
Institute for Plant Ecology
Justus-Liebig-University Giessen
Heinrich-Buff-Ring 26-32
D-35392 Giessen, Germany
Tel (Institute): ++49-(0)641-99-35333
Fax (Institute): ++49-(0)641-99-35309
Tel (private): ++49-(0)6406-3564
e-mail: Uwe1.Grueters at t-online.de







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