Nitrogen source effects on Al toxicity in nonmycorrhizal and mycorrhizal pitch pine (Pinus rigida) seedlings. I. Growth and nutrition

摘要

Previous studies indicated that the association ofPisolithus tinctoriuswith pitch pine (Pinus rigida) seedling roots prevented Al toxicity from developing when seedlings were exposed to 200ensp;mu;M Al in sand culture. The ectomycorrhizal fungus reduced seedling Al uptake and maintained P nutrition when seedlings were cultured on one-quarter strength Johnson's solution containing 3.5 and 0.5ensp;mMand, respectively. To broaden the scope of these findings, nonmycorrhizal and mycorrhizal seedlings were grown on one-quarter strength Johnson's solution modified to contain, NH4NO3, or. Seedlings were exposed to 0 or 200ensp;mu;M Al for 6 weeks. Reductions in seedling height growth rate and final shoot weight in response to Al occurred in nonmycorrhizal seedlings grown with. Root weights were consistently reduced by Al under all N-source combinations. Increasing proportions of, in the nutrient solution increased cation accumulation in roots and shoots and depressed tissue anion concentrations. The coprecipitation of Al and Piin roots of Al-treated seedlings further limited P availability in this treatment. Mycorrhizal infection maintained growth and foliar P levels under Al exposure, suggesting that Al-induced P limitation was a critical factor in nonmycorrhizal seedlings grown on primarily-based nutrient solutions.Key words:Pinus rigida, ectomycorrhizal, aluminium toxicity, nitrogen source.