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The detection of phytotoxic compounds, such as herbicides, environmental substances, polyphenols, xenobiotics, phytohormones is based on inhibition of photosynthetic electron transfer between PSII and PSI using chloroplast thylakoids from Vicia faba freshly isolated or lyophilized. The lyophilization of the biological unit ensures long-term stability and allows continuous supply without permanent cooling for more than one year. Within a few minutes the inhibition of photosynthetic electron flow by phytotoxic compounds is measured flurometrically. The increase of fluorescence induced by herbicides is shown to be correlated with a reduction inlight-dependent oxygen consumption. The site of inhibition by herbicides or other toxic compounds is indicated as the QB-binding site of the D1 protein inhibiting the plastochinon reduction. Another group of herbicides is anchored at cytochrom-b6/f-complex blocking the plastohydrochinon-oxidation. A third group of phytotoxins is able to perform redox interactions with photosystem-1 transferring them to oxygen which is consumed.

Fluorescence measurements using thylakoids offer all requirements as a preliminary screening tool for phytotoxic contamination. The biosensor is a very effective early warning system because of its low detection limit of 0.2-0.3 ug/L and the ability to indicate every photosynthetic active substance. .

Additional information

Authors: SCHNABL H, University of Bonn, Institute of Agricultural Botany (DE);TRAPMANN S, IRMM, JRC-Geel (BE)
Bibliographic Reference: Article: Bioeffects - Related Analytics - Coupling of Biorecognition to Chemical Identification, (1999)
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