Physiological Responses of Solanum nigrum L. Seedlings to Cadmium Stress

Physiological responses and cadmium (Cd)accumulation in Solanum nigrum L. seedlings under Cd stress were investigated by nutrient solution culture method. The results showed that Cd could affect the growth of Solanum nigrum L. seedlings, and had concentrationdependent and time-dependent effects. Cd stress also led to the decrease of leaf pigments contents. Average contents of Chlorophyll a(Chla), Chlorophyll b(Chlb)and carotenoid(Car)decreased 55.5%, 63.9% and 43.3% when Solanum nigrum L. seedlings subjected to high concentration of Cd(150 μmol·L-1). Furthermore, low Cd(25 μmol·L-1)improved root activities of Solanum nigrum L. seedlings significantly, and increased 10.4% compared to the control plants; Under high concentration of Cd, root activities of Solanum nigrum L. seedlings increased firstly and decreased, the submit was found after 10 d of Cd treatment. The relative elective conductivities, malondialdehyde(MDA)contents, soluble sugar contents and proline contents increased with increasing Cd concentration in the solution and along with treatment time; Compared to the control plants, they increased 17.7%, 117.7%, 5.6% and 95.3% under low Cd stress, and increased 39.0%, 194.6%, 56.3% and 758.0% under high Cd stress. Cd mainly accumulated in the shoot of Solanum nigrum L. seedlings, and Cd concentration in the plant tissues could be drawn as followed:leafstemroot, the maximum were detected after 20 d of high Cd stress, 1 287.25, 1 718.14 and 2 385.27 μg·L-1 DW of Cd concentrations in the root, stem and leaf, respectively.