Mycorrhizae
Arbuscular mycorrhizial fungi
(AM) has been found in association with plant roots all over the world.
A clear symbiotic relationship has been demonstrated whereby plants exude
photosynthates for the fungus to metabolize, in return, the fungus scavenges
for essential elements that may be rare in a particular soil. There is
some evidence that AM facilitates Cd uptake, but this varies with soil
conditions like Cd concentration and pH. Guo (1996) showed that AM increased
Cd uptake 37% in bean and 41% in maize. However, El-Kherbawy et al. (1989)
showed that AM increased Cd uptake in alfalfa at pH = 7.2, but reduced
Cd uptake at pH = 6.0, 6.7, pHs where Cd should have been more bioavailable.
Another study by Heggo et al. (1990) found AM increased Cd uptake in soybean
when the soil concentration of Cd was low, but reduced Cd uptake when the
soil Cd concentration was high. The mechanisms behind these phenomena are
not worked out, but clearly AM offers some potential to boost phytoextraction.
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