DYNAMICS OF LEAD ACCUMULATION IN MYCORRHIZAL AND NONMYCORRHIZAL NORWAY SPRUCE (PICEA-ABIES (L) KARST)

Twelve-week-old seedlings of Norway spruce (Picea abies (L.) Karst), n on-mycorrhizal or mycorrhizal with Laccaria laccata, Paxillus involutu s or Pisolithus tinctorius were exposed to 5 mu M Pb for either 32 or 42 days in a quartz sand-nutrient solution system. Ultrathin sections of mycorrhizal and non-mycorrhizal short roots were examined by X-ray microanalysis. After 42 days Pb treatment, the Pb content of the corte x cell walls was lower in the non-mycorrhizal short roots and in the P . involutus mycorrhizae than in the mycorrhizae of L. laccata or P. ti nctorius. The Pb content of the cell walls of the hyphal mantle was hi gher in P. involutus than in L. laccata or P. tinctorius. The short te rm experiment over 32 days showed that the Pb content of the cortex ce ll walls strongly increased during the first 16 days in the non-mycorr hizal roots and the L. laccata mycorrhizae, whereas it increased more slowly in the P. involutus mycorrhizae. After 32 days Pb treatment, th e Pb content in the cortex cell walls in the P. involutus mycorrhizae was similar to that in the non-mycorrhizal roots. P. involutus also de creased Pb translocation from the roots to the stems. Mycorrhizal infe ction was not affected by Pb but with P. involutus, the amount of extr amatrical mycelium was reduced by 50% on day 32 compared to day 16. Th e extramatrical mycelium of L. laccata was not reduced by Pb. It is co ncluded that ectomycorrhizal fungi differ in their effect on Pb accumu lation in the roots of Norway spruce. The binding capacity of the extr amatrical mycelium seems to be an important factor.