Copper mobility within the phloem is not clearly understood, due mainly to contradictory results (see Loneragan, 1981). Studies on the leaf Cu content of various plant species, however, have demonstrated substantial. There was a 40% decrease in the Cu content of leaves of onion during bulb development (Carolus, 1962). Loneragan et al. (1980) demonstrated large losses of Cu from leaves, in parallel with gains in Cu by the grain, for wheat grown at three levels of Cu supply