PROGRESS IN HERBICIDE DETERMINATION WITH THE THYLAKOID BIOASSAY

Chloroplast thylakoids are used as biological units to determine herbi cides in different kinds of water samples as well as in aqueous extrac ts of compost, soil or food samples. The thylakoid bioassy shows clear ly inhibition of fluorescence yield in the presence of photosystem II specific herbicides. Due to this method the ecotoxicological effect of samples with unknown pollutants can be tested fast and cost effective . It has been proven that all photosynthetic active compounds are reco rded at the same time because only additive interactions occur. Theref ore, the contamination level can be expressed as cumulative parameter for photosystem II active substances. Application was improved clearly by the addition of the radical scavenger sodium ascorbate to the isol ation media and by a higher concentration of the measuring medium. A n ew data evaluation method is described yielding in a lower detection l imit of 0.4 mu g diuron/l. The guidelines for the quality of water for human consumption with an allowable concentration of pesticides in gr oups is 0,5 mu g/l [1,2] and can be controlled with the thylakoid bioa ssay without performing any preconcentration steps.