MYCORRHIZAL COLONIZATION AND LEAD DISTRIBUTION IN ROOT TISSUES OF NORWAY SPRUCE SEEDLINGS

Non-inoculated spruce seedlings (Picea abies Karst.) and spruce seedli ngs colonized with Lactarius rufus Fr., Pisolithus tinctorius Coker & Couch or Paxillus involutus Fr. were grown for 35 or 37 weeks in a sys tem on two types of natural forest humus differing in Pb content. Usin g X-ray microanalysis, the distribution and content of Pb in the tissu es of mycorrhizal and non-mycorrhizal root tips were compared. No sign ificant difference in the Pb contents of root cortex cell walls of non -mycorrhizal and seedlings colonized by Lactarius rufus, Pisolithus, o r indigenous mycorrhizal fungi (mainly Tylospara sp.) was found. Howev er, in root tips of seedlings colonized by Paxillus involutus, due to a higher binding capacity for cations, the Pb content in cell walls of the root cortex were higher than in non-mycorrhizal roots. Pb content s in cell walls of the cortex of mycorrhizal and non-mycorrhizal roots were 3 times higher in plants growing in humus with a high Pb content than in plants growing in humus with a low Pb content. It is conclude d that increasing contents of Pb in the organic matter may lead to an increased loading of the apoplast with Pb. The mycobionts tested in th is investigation did not exclude Pb from root tissues.