Biochemical and physiological changes in jack bean under mycorrhizal symbiosis growing in soil with increasing Cu concentrations

The influence of jack bean [Canavalia ensiformis (L.) D.C.] mycorrhization, by the arbuscular mycorrhizal (AM) fungus Glomus etunicatum, in response to increasing Cu concentrations in soil (0, 50, 150 and 450 mg dm−3) was studied. In the highest Cu dose, mycorrhiza decreased Cu concentrations in plant organs and promoted biomass accumulation. In addition, mycorrhizal colonization was not affected by Cu suggesting certain tolerance of the inoculated AM fungus to this metal. Cu-induced proline accumulation and an increase in soluble amino acid contents in leaves, with higher proline contents in AM plants. Marked differences in foliar soluble amino acid composition were also observed in response to Cu in the soil. The activity of key antioxidant enzymes increased mainly in the leaves of non-AM plants, indicating increased production of reactive oxygen species. However, changes in malondialdehyde content were not observed suggesting an effective antioxidant system. Independent of mycorrhization, glutathione content in leaves decreased as Cu increased in the soil. Phytochelatins were detected in the leaves of both Cu treated and untreated plants, and quantitative and qualitative differences were observed due to mycorrhization. In summary, the AM fungus was able to maintain an efficient symbiosis with jack bean plants in soil containing high Cu concentrations. A combination of physiological and nutritional changes caused by the symbiotic association that might be of interest for phytoremediation strategies in Cu-contaminated soils.