More Evidence of Mycorrhizal Fungi as Arsenic Beater
By Douglas Barnes
As has been mentioned on this site before (See Beating Arsenic in Bengal and Bangladesh1), arsenic is a serious problem in many parts of the world killing hundreds of thousands of people each year. It can cause cancers in skin, bladder, kidney and lungs, cause gangrene by damaging blood vessels in the legs and feet, is suspected of aggravating or contributing to diabetes, high blood pressure and to fertility problems.
Now new research done in China3 using different species of mycorrhizal fungi finds that the fungi can also protect corn from arsenic contamination. Using Glomus species and Acaulospora species, the team found that the fungi reduced plant uptake of arsenic:
A pot experiment was conducted to examine the roles of indigenous and non-indigenous arbuscular mycorrhizal (AM) fungi in As uptake by maize (Zea mays L.) from original As-polluteded [sic] soil, and their effects on As and P fractions in the rhizosphere. The As-polluted soils with three As levels, were collected from As-polluted arable soil near an As mine. Indigenous AM fungi (M2: including Glomus spp., Acaulospora spp.) isolated from these soils were compared with a non-indigenous AM fungus (M1: Glomus caledonium 90036). The plants were harvested after 10 weeks of growth. Mycorrhizal colonization rate, dry weight (DW) and P, As concentrations in plants, as well as As and P fractions, were determined. Compared to the non-mycorrhizal treatment, at the high soil As level, maize inoculated with AM fungi had higher shoot and root DW and P contents, both M1 and M2 inoculations increased As accumulation in root, though M1 reduced shoot As content, and M2 transported more As from roots to shoots. M1 decreased root and shoot As contents at the low and medium soil As levels. Plants mainly took up non-specifically sorbed As at the high soil As level, but As was taken up from hydrous oxides of Fe and Al at the low and medium soil As levels. All results indicate that indigenous consortia M2 could protect their host plants from the toxicity of excessive As through P nutrition by activating P, though non-indigenous M1 could alleviate As toxicity through stabilizing As and P in the soil.
It is reasonable to expect that other plants that form mycorrhizal associations would also have reduced arsenic uptakes from Glomus species and likely Acaulospora species as well. In arsenic-contaminated regions, it would be a good idea to inoculate soils with Glomus species4 and avoid practices that hinder mycorrhizal growth (ploughing, adding synthetic nitrogenous fertilisers, addition of too much phosphorus).