Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 500805487
Project actuator technology
At the Laboratory of Adaptive Lighting Systems and Visual Processing, multi-channel LED luminaires are built using chip-on-board LED technology. A chip-on-board LED contains 9 wavelengths (360 nm, 405 nm, 450 nm, 520 nm, 600 nm, 660 nm, 730 nm, warm white and 900 nm). For this purpose, a special driver is designed for the chip-on-board LEDs. The features of this driver are wide frequency range (100 Hz – 20 Khz), current (100 – 750 mA) and duty cycle (10 – 98%). All LED chips are controlled separately. A human machine interface (HMI) software is also programmed. In addition, the wavelength light lines for the different wavelengths are designed, simulated and implemented. The finished lights will be characterized with a measurement system (U-ball, Peltier module, Thorlab devices, spectrometer). Consequently, the intensities (1200, 600, 300, 200, 100, 50 µmol/ m2s = 6 photon densities), wavelength, clocking and the combinations of the multi-channel LED lights for photosynthesis research are managed. In the Applied Plant Science Laboratory, the suitable plant species are cultivated and researched with the generated light conditions. The research variables are a total of 6 spots x 6 frequencies x 9 radiation spectra x 6 intensities.
Project sensor technology
Leaf temperature is measured with two temperature sensors and infra-red camera. The leaf color is determined by spectral reflectance. A very important work chain is the “Multivariate Fluorescence – based Prediction – Model”. The aim of this work chain is to represent the photosynthetic rate determined by gas exchange analysis as a function of the parameters determined by chlorophyll fluorescence analysis, leaf reflectance and leaf absorption data, and leaf temperature determined by thermography. It is similar to the study by Losciale et al. (), but with a much larger number of input parameters and more focus on the effects of the light factor. The above parameters are measured simultaneously: Photosynthetic rate by gas exchange analysis with a gas exchange system, fluorescence analysis with an imaging PAM system, temperature, reflectance, and absorbance data as described in the paper so cited above. Both the imaging PAM system and the gas exchange system are available in the APS working group. https://doi.org/10.1104/pp.113.225243
Modeling = photosynthesis as light – function
Photosynthesis will be analyzed separately for each plant species. Then, the data at each growth stage will be considered, since it can be assumed that the leaf property (reflection, absorption, leaf thickness, leaf texture) changes with the growth stage. At each point along the time axis of the growth process, exemplary wavelengths (e.g., 450 nm and 660 nm) and two current levels will be used to analyze the photosynthetic rate as a function of frequency and duty cycle. Two possible solutions emerge. If the photosynthesis rate is independent of frequency and duty cycles, the results of all frequencies and duty cycles are combined. If the photosynthetic rates are dependent on frequency or duty cycle after a statistical significance test, the frequencies and duty cycles are considered as independent variables. The data are then grouped into different frequencies and duty cycles. An energy consideration for some desired photosynthetic rates will be performed at this point. From this, a range of preferred frequencies and duty cycles can be determined from an energy and economic perspective. The number of parameters can thus be reduced. What remains are the parameters of leaf temperature, wavelengths, and irradiances for each plant species at each defined growth time.
At each leaf temperature, the photosynthetic rate can be plotted as a function of wavelength and radiation intensity. At different leaf temperatures, there are different functions and at different growth stages, there is a set of functions. Thus, the required photosynthetic rate can be found by entering the vector V = f (leaf temperature, wavelength, radiation intensity, frequency) into the data structure.