CADMIUM UPTAKE IN NORWAY SPRUCE (PICEA-ABIES (L) KARST) SEEDLINGS

Root elongation of Norway spruce (Picea abies (L.) Karst.) seedlings was inhibited in the presence of 5-mu-M Cd but was unaffected by a Cd concentration at 0.05-mu-M. Nutrient solutions labeled with Cd-109 were used to investigate the influence of pH, cations and the metabolic inhibitor 2,4-dinitrophenol (DNP) on the uptake of Cd by roots of intact spruce seedlings. Extracellular Cd was removed by washing the roots, and the relative amounts of Cd in the root apoplast and symplast estimated. In the presence of DNP, Cd uptake was reduced at 0.05-mu-M (non-toxic) but not at 5-mu-M Cd (toxic). At 0.05-mu-M Cd, the uptake of Cd into both the apoplast and symplast was dependent on the pH of the nutrient solution. Lower pH decreased Cd accumulation. Aluminum supplied at 100 or 500-mu-M lowered the Cd concentrations of both the apoplast and symplast. An increase in Ca or Mg supply reduced the Cd concentration of the apoplast but not of the symplast. In the presence of 5-mu-M Mn, the concentration of Cd in the symplast decreased by 44% compared to the control (1-mu-M Mn). High concentrations of Zn or Hg did not affect the Cd concentration of the roots.