Effects of heavy metal (Pb) on arbuscular mycorrhizal fungi in vitro

The responses of Ri-TDNA-transformed roots and arbuscular mycorrhizal fungi established on Ri-TDNA-transformed roots to lead-amended media was investigated in vitro. At exposure to increasing concentrations of lead (2-10 mg/l[ppm]), three Ri-TDNA-transformed root clones viz., Swa, Swb and Swc, exhibited profuse growth. At exposure to increasing concentrations of lead (0.1-5 ppm), the dual cultures of Ri-TDNA-transformed roots and arbuscular mycorrhizal fungi., Glomus lamellosum/Swa, Glomus intraradices/Swb and Glomus proliferum/Swc, exhibited tolerance to 5 ppm of lead. When subjected to one physiological stress, either exposure to Pb or inoculation with AM fungi, Ri-TDNA-transformed root clones exuded more phenols in the growth medium than retained in the roots. When subjected to dual physiological stress, mycorrhizal Ri-TDNA-transformed roots growing on Pb-enriched medium, the total phenol content increased in the roots and exudation into the medium decreased. © 2008 Springer Science+Business Media B.V.