THE EFFECT OF PAXILLUS-INVOLUTUS FR ON ALUMINUM SENSITIVITY OF NORWAYSPRUCE SEEDLINGS

Non-mycorrhizal Norway spruce seedlings (Picea abies Karst.) and Norwa y spruce seedlings colonized with Paxillus involutus Fr. were grown in an axenic silica sand culture system. After successful mycorrhizal co lonization, the seedlings were exposed to 200 or 800 muM AlCl3 for 10 weeks. In both non-mycorrhizal and mycorrhizal seedlings, exposure to Al significantly reduced root growth and the uptake of Mg and Ca. Afte r 5 weeks of exposure to 800 muM Al, the mycorrhizal seedlings had sig nificantly higher chlorophyll concentrations than the non-mycorrhizal seedlings, although no difference in Mg nutrition was apparent. After 10 weeks of exposure to Al, both non-mycorrhizal and mycorrhizal seedl ings exhibited needle chlorosis and reduced photosynthetic activity. H owever, the aluminum-induced reduction in shoot growth was largely ame liorated by colonization with P. involutus. We conclude that mycorrhiz al colonization modifies the phytotoxic effects of Al in Norway spruce seedlings. However, differences in physiological responses to Al betw een mycorrhizal and non-mycorrhizal seedlings may be largely reduced i n the long term as a result of impaired mineral nutrient uptake.