Influence of physiological growth parameters on duckweed (Lemnaceae) in a re circulating and vertical cultivation system Duckweeds (Lemnaceae) are the fastest growing angiosperms on earth. Five different genera compromising 36 species of these floating freshwater plants are distributed around the world. They are highly interesting for different fields of application due to their fast growth rate and biomass production their high nutritional value and their variability of nutritional composition which can be influenced by cultivation conditions. For industrial purposes large amounts of duckweed with a certain quality are required at any time of the year. Therefore a standardized production process with a focus on plant physiological growth parameters is needed. For this dissertation the effect of the nutrient medium especially the nitrate N to ammonium N ratio and nutrient concentration on the relative growth rates (RGRs) and crude protein contents (CPCs) of two duckweed species (Lemna minor and Wolffiella hyalina) was investigated under non axenic cultivation conditions. Furthermore the effect of different light intensities and spectral distributions on RGR CPC and chlorophyll a content was investigated using a small scale indoor vertical farm under non sterile cultivation conditions. Based on these results and experiences with the previously used cultivation systems a large scale Indoor Vertical Farm was developed. It consists of nine vertically stacked production basins (1.95 x 1.45 x 0.1 m) resulting in a total production area of ca. 25.5 m2. The nutrient solution is re circulating within the system and the nutrients are dosed automatically based on the electrical conductivity. Most abiotic growth parameters are controllable and adjustable. During a 40 day production phase a total of 35.6 kg of fresh L. minor biomass was harvested which corresponds to ca. 900 g per day.