Fig. 2. Change in Cu speciation of Davis Minimal Medium (DMM) soil extract test medium as determined by the percentage of total copper concentration ([Cu]_tot) present as Cu–citrate (circles) and Cu–ligand (squares) complexes. (A) The effect of concentration of ligand (L) at fixed [Cu]_tot = 0.5 µM and fixed log K(Cu–L) = 5. (B) The effect of log K(Cu–L) value at fixed [L] = 0.2 mM and fixed [Cu]_tot = 0.5 µM.