Development of a well-defined monitoring-system to ensure optimized plant production in the DLR Greenhouse Module

Abstract

The goal of this diploma thesis was the analysis and evaluation of environment and growth parameters in the DLR GM, which would have to be monitored continuously to maintain optimal environmental conditions for plant growth and to protocol productivities and growth of plant cultivars. The perspective of evaluation plant growth parameters is focused on parameters which are representative for the whole canopy in a growth chamber or a growth chamber compartment. Indicative parameters should be of such kind that their interpretation can be done independently of the plant species without a deeper insight in plant physiological contexts. The analysis was directed to possible application in projects for space exploration and plant cultivation at terrestrial extreme locations. To achieve the above mentioned goal specific publications were analysed for contents regarding plant cultivation in closed artificial environments in combination with literature on plant ecology, plant nutrition and net photosynthesis. The following conclusions have been drawn finally: (1) Plant productivity in terms of fresh biomass and dry mass can be determined continuously from fluxes of carbon dioxide and water, which have to be detected in any case during operation of a closed habitat. (2) It may be questioned whether a quantitative and qualitative monitoring of volatile organic compounds is necessary, since the continuous and active elimination of these compounds would be a standard obligation for the atmosphere control system in closed habitats and environments. (3) Application of microwave spectroscopy promises to be useful for in vivo-monitoring of shoot growth. (4) The hydroponics can be carried out with the liquid film technique in such a way, that little waste is produced and evaporation from the nutrient solution is small in comparison to transpiration, but in this case monitoring of dissolved organic carbon (DOC) or total organic carbon (TOC) can be informative. It may be proposed for this purpose to apply online techniques which are in use in modern water analysis. It might be checked, whether the flame ionization technique common in gas chromatography is also applicable for DOC quantification. (5) Monitoring of the concentration of all essential nutrients does not seem to be necessary to prevent nutrient deficiency or toxicity. If certain principles for the composition and concentration of the minerals in the nutrient solution are followed, it is sufficient to measure the concentration of pH and the whole nutrient strength.