Affiliation: | Biotechnology Unit, Toxic Substances Division, Department of the Environment, Romney House, 43 Marsham Street, London SW1P 3PY;AFRC Institute of Arable Crops Research, Rothamsted Experimental Station, Harpenden, Herts. AL5 2JQ;Natural Environment Research Council, Polaris House, North Star Avenue, Swindon, Wilts. SN2 1EU |