Comparison of subcellular distribution and chemical forms of cadmium among four soybean cultivars at young seedlings.

The hydroponic experiment was carried out to investigate the Cd subcellular distribution and chemical forms in roots and shoots among four soybean seedling cultivars with two Cd treatments. HX3 and GC8, two tolerant and low-grain-Cd-accumulating cultivars, had the lowest Cd concentration in roots and high Cd concentration in shoots, while BX10 and ZH24, two sensitive and high-grain-Cd-accumulating cultivars, had the highest Cd concentration in roots and the lowest Cd concentration in shoots at young seedling stage. Furthermore, the sequence of Cd subcellular distribution in roots at two Cd levels was cell wall (53.4-75.5 %) > soluble fraction (15.8-40.4 %) > organelle fraction (2.0-14.7 %), but in shoots, was soluble fraction (39.3-74.8 %) > cell wall (16.0-52.0 %) > organelle (4.8-19.5 %). BX10 and ZH24 had higher Cd concentration in all subcellular fractions in roots, but HX3 and GC8 had higher Cd concentration of soluble fraction in shoots. The sequence of Cd chemical forms in roots was FNacl (64.1-79.5 %) > FHAC (3.4-21.5 %) > Fd-H2O (3.6-13.0 %) > Fethanol (1.4-21.8) > FHCl (0.3-1.6 %) > Fother (0.2-1.4 %) at two Cd levels but, in shoots, was FNacl (19.7-51.4 %) ≥ FHAC (10.2-31.4 %) ≥ Fd-H2O (8.8-28.2 %) ≥ Fethanol (8.9-38.6 %) > FHCl (0.2-9.6 %) > Fother (2.5-11.2 %). BX10 and ZH24 had higher Cd concentrations in each extracted solutions from roots, but from shoots for GC8 and HX3. Taken together, the results uncover that root cell walls and leaf vacuoles might play important roles in Cd detoxification and limiting the symplastic movement of Cd.