A FAST BIOASSAY FOR PHYTOTOXICITY MEASUREMENTS USING IMMOBILIZED PHOTOSYNTHETIC MEMBRANES

The potential of thylakoid membranes immobilized in an albumin-glutaraldehyde crosslinked matrix in a fast bioassay for phytotoxicity measurements in aqueous samples is studied. Free and immobilized preparations are compared for their electron transport activity measured as the initial rate of oxygen evolution with 2,5-cichlorobenzoquinone as the artificial electron acceptor. Immobilized thylakoids were much more stable under storage conditions; in the dark, at 4 degrees C, they were fully stable in terms of photosynthetic activity for a period of 200 h. The immobilized membranes were as sensitive as the free thylakoids for the detection of most of the compounds tested (metal cations, sulfite, nitrite, and herbicides), all known as inhibitors of photosynthetic electron transport. In some instances, the immobilized preparations were even more sensitive than the free counterparts. The sensitivity could be further increased by lowering chlorophyll concentration in the assay. The short incubation period required (similar to 10 to 15 min) and the small volume of the assay (3 mt) suggest that this type of material should be useful in the detection of locations or effluents with phytotoxic character. (C) 1994 John Wiley & Sons, Inc.