Phytotoxicity of compost in various degrees of maturity has been extensively reported. It is usually determined by a seed germination index assay or by plant growth tests. The main deficiency of these tests is the length of time required for their performance. Therefore, we tested new biosensor techniques in this study based on oxygen consumption and fluorescence measurements of isolated freshly suspended or lyophilized chloroplast thylakoids (Vicia faba L.). These methods were compared with traditional phytotoxicity tests. The new systems proved to be suitable for evaluating the function of the photosynthetic electron transport (PET) between photosystem II and photosystem I. When PET was inhibited by phytotoxic substances, fluorescence increased whereas oxygen consumption decreased. Germination index data as well as plant growth bioassay data exhibited high correlations with data obtained from the novel biosensor techniques. Thus, we propose application of these methodologies based on freshly isolated or lyophilized chloroplast membranes, as rapid and sensitive tests for compost phytotoxicity.
Bibliographical noteFunding Information:
This research project was supported to H. S. and Y. C. by the DFG (Deutsche Forschungsgemeinschaft), Bonn, Germany. The authors are thankful to the DFG for this support. Lyophilized thylakoids were prepared by S. Trapmann, Institute for Reference Materials and Measurements, Joint Research Centre, European Commission, Geel, Belgium. The institute is gratefully acknowledged for providing the lyophilization process. G. Jende is gratefully acknowledged for her assistance in working out the extraction procedure.