An X-ray Microanalytical Study of the Distribution of Cadmium in Roots of Zea mays L

X-ray microanalysis of roots of Zea mays L. grown in the presence of cadmium, revealed that the absorbed metal is removed by normal electron microscope preparative procedures. Following pretreatment with either phosphate or sulphide to immobilize cadmium, the metal was detected in the walls of the sieve elements and in the middle lamella separating the endodermis from the pericycle. These findings suggest that cadmium is principally bound to ion exchange sites on pectic residues in the cell wall.