In vitro phytotoxicity screening test using immobilized spinach thylakoids

Several pollutants found in water inhibit the photosynthetic electron trans port chain, and therefore affect the growth of phytoplankton and aquatic pl ants. In this study, thylakoid membranes isolated from spinach leaves were used in a microelectrochemical cell to generate photocurrent. The toxic eff ect of an inhibitor is observed by a decrease in the photocurrent. To impro ve the stability of their biological functions, the thylakoid membranes wer e immobilized in an albumin-glutaraldehyde cross-linked matrix. The develop mental work of this phytotoxicity test was done by using the herbicide atra zine as the reference toxicant. Results on reproducibility were in the rang e generally accepted for standardized bioassays. The phytotoxicity of herbi cides from various chemical classes including photosynthetic and nonphotosy nthetic inhibitors was evaluated. Toxicity responses of the immobilized thy lakoid test to photosynthetic inhibitors compared favorably with literature data for the algal growth inhibition test using Selenastrum capricornutum. The detection capabilities of the photosynthetic microassay for cyanazine, metribuzin, diuron, and propanil met the recommandation for the water qual ity guidelines for raw water. Characteristics of this in vitro approach suc h as rapidity, experimental simplicity, and cost effectiveness are also dis cussed.