TRANSLOCATION OF COPPER IONS IN PLANTS

IN Nature of December 26, 1936 (p. 1099)1, a method is described by A. C. Léeman for destroying Dichapetalum, a noxious weed of the Transvaal, by plastering a mixture of copper sulphate, calcium chloride and ordinary soil upon a short length of underground stem from which the 'bark' had been removed. Within twenty-four hours, leaves 15 ft. from the main stem were practically dead or dying, the downward movement being much slower (the ratios of the rates calculated from Léeman's figures being about 30: I). The movement of the copper ions was followed by placing freshly cut sections in a solution of potassium ferrocyanide, when a more or less deep red-brown colour could be seen where the copper arrived or accumulated. It was found that the movement took place "essentially" in the phloem, and it was suggested that the method could be used for the study of the translocation of solutes as such, the advantage being that the copper enters the intact sieve-tubes laterally by diffusion.