LEAD INFLUENCES ROOT-GROWTH AND MINERAL-NUTRITION OF PICEA-ABIES SEEDLINGS

Seedlings of Picea abies (L.) Karst. were grown in nutrient solutions containing a range of Pb concentrations. A 4-week exposure to 0.5-mu-M Pb reduced the growth of primary, secondary and tertiary roots. The initiation of lateral roots appeared to be more sensitive to Pb than the growth of already formed roots. After a 9-week exposure to a range of Pb concentration (0.1-2-mu-M) the levels of Pb in roots increased with increasing Pb supply. The Pb levels in roots were higher than in needles by a factor of 100 - 300. The Pb levels in roots were strongly dependent upon the pH of the nutrient solution and decreased at lower pH. With the exception of decreased levels of Ca, Fe and Zn in root tips (5 mm) exposure to Pb only slightly affected the levels of other mineral elements in the roots. In needles, the Ca and Mn levels decreased after exposure to all Pb concentrations.