1. Central Radioisotope Laboratory, Medical Faculty 1, Charles University, Na bojišti 3, 121 08 Prague 2, Czech Republic, Isotope Laboratory, Institute of Experimental Botany, Vídeňská 1083, 142 20 Prague 4, Czech Republic, Department of Pathophysiology, Palacký University, 775 15 Olomouc, Czech Republic, CNRS, Station Biologique, 29680 Roscoff, France, Chemistry and Chemical Technology Department, University of Bradford, Richmond Road, Bradford, West Yorkshire BD7 1DP, U.K., and Laboratory of Growth...