The Geisenheim FACE Experiment

MONITORING-PAM

The FACE (Free Air Carbon Dioxide Enrichment) site of the Hochschule Geisenheim and a similar site of the Justus Liebig-Universität Giessen form the experimental backbone of the LOEWE research cluster “FACE2FACE”. With substantial support from the state of Hessen, researchers strive to understand how elevated CO2 of the earth’s future atmosphere affects life.

Being the outstanding center of German grapevine breeding and research for almost 150 years, the Hochschule Geisenheim naturally includes grapevine plants in their FACE research program. Currently, a white and a red grape variety are investigated: Riesling and Cabernet Sauvignon, respectively.

MONITORING-PAM employed in
FACE experiment

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Led by Dr. Manfred Stoll, the Geisenheim research group records long-term effects on photosynthesis with two MONITORING-PAM systems, each capable of surveying simultaneously four samples. The MONITORING-PAMs determine data of Y(II) which indicate the efficiency of photosystem II to convert absorbed light into chemical energy. Figure 1 shows averages of 14 diurnal measurements of Y(II) carried out in June 2014.

These daytime measurements were accompanied by experiments at night in which the response of Y(II) to increasing light intensities (PAR) from the MONI measuring heads was recorded. From Y(II) and PAR, photosynthetic electron transport rates were calculated and plotted against the respective PAR values (Fig. 2).

Based on these “light response curves”, acclimation state and maximum capacity of photosynthesis can well be assessed. The Geisenheim grapevine researchers crosscheck MONITORING-PAM data by CO2 gas exchange measurements using a GFS-3000 device. Apart from photosynthesis, the project is expected to yield general insights into plant growth, berry development, and wine quality under future climate conditions.

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