Fig. 1.

Inoculation and Cd treatment systems of Allium cepa and Gigaspora margarita (A & D), and Lotus japonicus—Rhizophagus irregularis (B & C) arbuscular mycorrhizas. (A) A plastic Petri dish root box system (90 mm diam, 15 mm depth.). From 80 to 86 dai, 50 ppm Cd nitrate in water was added every day until harvest. (B) One-compartment system (C1). A seedling and spores were cultivated in Cd-contaminated soil (200 ppm Cd chloride). (C) Five-compartment system (C5). An acrylic box (14 cm length × 10 cm width × 10 cm depth) was divided into 5 by nylon mesh (37 μm), which only hyphae could pass through. The middle three compartments contained only soil (field soil : river sand = 2:1) and the two outermost compartments contained Cd-contaminated soil (200 ppm Cd chloride, field soil : river sand = 3:1). Seedlings and spores were placed in the center compartment, which was sandwiched between two buffer compartments; therefore, only extraradical hyphae of R. irregularis extended into the outermost compartments and were exposed to Cd. (D) An extraradical hyphal network on a cellulose acetate membrane by establishment of A. cepa—G. margarita arbuscular mycorrhiza. Arrows, auxiliary cells; ns, newly formed spore.