Role of AM Fungi in the Uptake and Accumulation of Cd and Ni by Luffa aegyptiaca

Sponge gourd (Luffa aegyptiaca) was grown in pots with and without inoculation with two arbuscular mycorrhizal (AM) fungi, viz., Glomus macrocarpum and Glomus monosporum singly and in combination. Seven-day-old plants were treated with 18.9 μg Cd g⁻¹ soil and 155.4 μg Ni g⁻¹ soil alone and in combination. At 90 days old stage, dry weight of root, shoot, and fruit; uptake of heavy metals in root, stem, leaves, and fruits; percent mycorrhizal root colonization; and spore number in the root zone were determined. When applied singly, the uptake of Cd and Ni in host plants was enhanced more effectively by G. monosporum than G. macrocarpum. The larger proportion of Cd uptake in uninoculated host was retained in the roots but in inoculated plants (with both Glomus sp.), major amounts of the Cd were translocated to the above ground parts including fruits. The leaves were the main sinks of Ni in inoculated plants. The overall tissue burden of both heavy metals in the host was enhanced relatively more effectively on association with G. monosporum as compared with G. macrocarpum. The uptake of Cd was relatively higher in plants treated with both the metals and both the AM fungi. Despite the relatively higher uptake of both the heavy metals in inoculated plants, the host dry weight was significantly higher compared with uninoculated plants. The percent mycorrhizal root colonization of the host by both AM fungi was higher in plants grown without either of the heavy metals. The combined application of both the heavy metals reduced the spore density in the root zone soil of host. The results show that the AM fungi enhanced the uptake of Cd and Ni by the host but alleviated the toxicity by promoting plant growth.