Effects of Soil Cadmium on Growth and Physiological Characteristics of Solanum nigrum L. Plants

Solanum nigrum L. has been discovered to be a Cd hyperaccumulating species, and is therefore used for phytomining and phytoextracting Cd contaminated soils. In this work, the effects of cadmium on nutrients [nitrogen(N), Phosphorus(P)and potassium(K)] absorption and plasma membrane ATP activity in S. nigrum were investigated in a soil culture experiment. Results showed that lower Cd treatments(≤40 mg·kg- 1) enhanced plant growth and biomass accumulation, whereas higher Cd(40 mg·kg- 1) inhibited plant growth. Leaf chlorophyll a(Chla), chlorophyll b(Chlb)and total chlorophyll(Chl)contents were increased by 10 mg Cd·kg-1, but decreased at higher Cd doses. With increasing Cd rates, the contents of N, P and K in roots, stems, leaves and fruits firstly increased and then decreased, except P in the stem, while the Cd accumulation in root, stem, leaf and fruit kept increasing, with leafstemrootfruit. In addition, the content of malondialdehyde(MDA)and the activities of catalase(CAT)and superoxide dismutase(SOD)increased with increasing Cd doses, while peroxidase(POD)activity showed a upside downVtrend. However, shoot(leaf plus stem)and root H+-ATPase activities and root Ca2+-ATPase activity decreased, but the activity of shoot Ca2+-ATPase firstly increased and then decreased as Cd rates increased. Results obtained in this study suggest that S. nigrum plants may tolerate high Cd(≥40 mg·kg-1)through accelerating the accumulation of Cd ions in root, improving antioxidant enzymes(CAT and SOD) activity, decreasing POD and plasma membrane ATP activity, and enhancing N, P, and K absorption.