suitable model systems for the investigation of biochemical process in plants, plant-environment interaction : biochemical adaptions; C3-C4 plants; acid metabolism of Crassulaceae, Temperature (high, low, flooding, drought, soil (selenium, heavy metalls), salt (chlorids, sulfates) environmental poisons, plant-animal interactions (pollination-flower colour; damage protection, odorous compounds, pheromones), plant-microorganism ineraction (phytoalexins, pre- and postinfectional compounds), plant-plant interaction