Soil contamination with phenanthrene induces maize mycorrhiza growth suppression

Abstract

Soil pollution with polycyclic aromatic hydrocarbons (PAH) such as phenanthrene is extremely detrimental to the environment and to all living organisms, which is why appropriate remediation techniques are required. Here we tested single and combination effects of the arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis BEG 87 and a soil amendment that results from the fermentation of organic matter through the activity of efficient microorganisms (Bokashi) on maize (Zea mays L.) growth performance, when exposed to phenanthrene. Main results showed that phenanthrene reduced total maize dry biomass, though only in mycorrhizal plants. The AMF root colonization respectively increased and decreased with Bokashi and phenanthrene. Growth suppressions in maize with AMF are common, but to our knowledge this has not been shown in combination with PAH. Possible mechanisms involved in this growth suppression could be related with increased phenanthrene uptake and hence increased plant toxicity or that phenanthrene impaired possible benefits from AMF in terms of nutrient acquisition, which could have resulted in the imbalance of the cost-benefit of the mycorrhizal association leading to growth suppression. However, the underlying mechanisms for this observed negative mycorrhiza growth response in maize when exposed to phenanthrene remains to be identified.