1. P. E. Tiku, A. Y. Gracey, A. I. Macartney, A. R. Cossins, Environmental Physiology Research Group, Department of Environmental and Evolutionary Biology, University of Liverpool, Liverpool L69 3BX, UK.
2. R. J. Beynon, Department of Applied Biochemistry and Molecular Biology, University of Manchester Institute of Science and Technology, Manchester M60 1QD, UK.