Direct effects of soil cadmium on the growth and activity of arbuscular mycorrhizal fungi

A compartment cultivation system was developed to study the effect of cadmium (Cd) in soil on the development of arbuscular mycorrhizal fungi (AMF) under the same host conditions. Fungal compartments consisting of four levels of Cd addition rate (0, 5, 25 and 50 mg kg(-1)) were inserted into each porcelain pot in the greenhouse. Mycorrhizal development by Glaroideoglomus etunicatum and Glaroideoglomus claroideum was determined at three growth stages of Cucumis sativus. Both AMF isolates showed good root colonization during plant growth. Total extraradical mycelium (ERM) length and active ERM length reached a maximum at low Cd addition rate (5 mg kg(-1)) and were inhibited at the higher Cd addition rate (25 and 50 mg kg(-1)). The two AMF isolates showed different responses to Cd addition at the three growth stages and G. claroideum seemed to be more tolerant to Cd toxicity. These results showed a potential to use this technique to study the function of soil-grown AMF hyphae.