Zn pollution counteracts Cd toxicity in metal-tolerant ectomycorrhizal fungi and their host plant, Pinus sylvestris

Authors

  • Erik Krznaric,

    1. Hasselt University, Centre for Environmental Sciences, Environmental Biology Group, Agoralaan, Gebouw D, 3590 Diepenbeek, Belgium.
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  • Jan H. L. Wevers,

    1. Hasselt University, Centre for Environmental Sciences, Environmental Biology Group, Agoralaan, Gebouw D, 3590 Diepenbeek, Belgium.
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  • Christophe Cloquet,

    1. Ghent University, Department of Analytical Chemistry, Krijgslaan 281 – S12, 9000 Ghent, Belgium.
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    • Present address: CRPG, Centre de Recherches Pétrologiques et Géochimiques, 15 rue Notre Dame des Pauvres, 54501 Vandoeuvre lès Nancy, France.

  • Jaco Vangronsveld,

    1. Hasselt University, Centre for Environmental Sciences, Environmental Biology Group, Agoralaan, Gebouw D, 3590 Diepenbeek, Belgium.
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  • Frank Vanhaecke,

    1. Ghent University, Department of Analytical Chemistry, Krijgslaan 281 – S12, 9000 Ghent, Belgium.
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  • Jan V. Colpaert

    1. Hasselt University, Centre for Environmental Sciences, Environmental Biology Group, Agoralaan, Gebouw D, 3590 Diepenbeek, Belgium.
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E-mail jan.colpaert@uhasselt.be; Tel. (+32) 11 268304; Fax (+32) 11 268301.

Summary

Adaptive Zn and Cd tolerance have evolved in populations of the ectomycorrhizal fungus Suillus luteus. When exposed to high concentrations of both metals in vitro, a one-sided antagonism was apparent in the Zn- and Cd-tolerant isolates. Addition of high Zn concentrations restored growth of Cd-stressed isolates, but not vice versa. The antagonistic effect was not detected in a S. luteus isolate from non-contaminated land and in Paxillus involutus. The fungi were inoculated on pine seedlings and subsequently exposed to ecologically relevant Zn and Cd concentrations in single and mixed treatments. The applied doses severely reduced nutrient acquisition of non-mycorrhizal pines and pines inoculated with metal-sensitive S. luteus. Highest translocation of Zn and Cd to shoots occurred in the same plants. Seedlings inoculated with fungi collected from the polluted site reduced metal transfer to their host and maintained nutrient acquisition under high metal exposure. The isolate showing highest tolerance in vitro also offered best protection in symbiosis. The antagonistic effect of high Zn on Cd toxicity was confirmed in the plant experiment. The results indicate that a Zn- and Cd-polluted soil has selected ectomycorrhizal fungi that are able to survive and protect their phytobiont from nutrient starvation and excessive metal uptake.

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