Philipp Bokatius, Gudrun Mende, Matthias Rang, Peter Stolz, Jenifer Wohlers

In last year's annual report, we described the successful completion of the “Further Development of Fluorescence Excitation Spectroscopy” project, in which a new facility for fluorescence excitation spectroscopy (Fluoreszenz-Anregungs-Spektroskopie, FAS) was set up. In the meantime, the modernization of Jürgen Strube's original system has also been completed and a follow-up project has been started. This project uses the new measurement technology to address both fundamental and application-specific issues relating to systemic and immaterial influences on the living and developmental conditions of plants, animals, and humans.

Series of Measurements Taken

Suitability for different sample types (leaves, roots, soil, etc.) was investigated this year in ten sample series. The influence of “breeding method” or “cultivation/handling of the plants” was examined for spinach, carrots, wild carrots, lightroot, broccoli (two series), sweet maize, and grain maize. Soil samples were also processed. In chlorophyll-containing (green) sample material, such as spinach or broccoli, the influence of the grower was not so easy to recognize. This may be due to a possible influence on the long-term fluorescence by the light affinity of the chlorophyll. In the root samples (carrot, lightroot) and in the maize samples, breeding influences could be observed by means of the increasing broadband excitability. Phenomenon series about this are planned for the following year. Grapes, which were grown with and without the use of preparations, were examined in a different context and showed a similar effect for the preparations. Two series of samples were carried out with processed products.

Expansion of Measurement Options

In addition to the quality investigations, methodological development is another area of the project. This includes evaluating the applicability to previously unmeasured sample types. For example, blood samples were examined for the first time, partly with the goal of evaluating the most economical use of sample material. A dilution in water of 1:20 gave very good results that were similar to the results of undiluted samples.

Further development of the method included increasing the efficiency of detection in order to be able to measure smaller sample volumes. With small samples, such as apple cores, it is possible to increase the detectable proportion of emitted light by using a concave mirror that focuses the light emitted by the sample from all sides. A concave mirror has been designed and built, and the first test measurements show that the detection sensitivity is increased by a factor of 20 compared to conventional measurements without a mirror.

In particular, we have worked on further developing the newly accessible spectral resolution of fluorescence light, which is achieved using filters. A new set of filters was produced and optimized, which improves the precision of the measurement and gives us greater flexibility. The filters can be used to create different spectral “windows”, i.e. frequency ranges, including narrowband frequency ranges, like with classic bandpass filters, as well as single-sided broadband frequency ranges (longpass filters). Various test measurements were carried out, with more to follow, that investigate the value of this new possibility for the FAS-2 system.

Finally, there were also optimizations in data management, evaluation methods, data export, and the programming of the two systems.

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