Effects of Intercropping with Different Solanum Plants on the Physiological Characteristics and Cadmium Accumulation of Solanum Nigrum

ABSTRACT To improve the ability of hyperaccumulators to take up cadmium (Cd), the effects of the intercropping of various Solanum plants [Solanum diphyllum L., Solanum alatum Moench, and Solanum nigrum Linn. var. humile (Bernh.) C. Y. Wu et S. C. Huang] on the Cd accumulation characteristics of Solanum nigrum L. were studied. The results indicated that the biomasses and Cd contents of all parts of intercropped S. nigrum and S. nigrum var. humile plants increased by varying degrees relative to the levels in the corresponding monocultured plants. However, the biomasses and Cd contents of S. diphyllum and S. alatum decreased in response to intercropping. Additionally, the photosynthetic pigment contents (chlorophyll a, chlorophyll b, and carotenoids) and the antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) activities of the intercropped S. nigrum and S. nigrum var. humile plants tended to increase. Moreover, the intercropping with S. nigrum var. humile significantly increased the amount of extracted Cd in the S. nigrum roots, stems, leaves, and shoots by 136.86%, 133.67%, 177.45%, and 169.40%, respectively, relative to the corresponding amounts in the S. nigrum monocultured plants. The intercropping of S. nigrum with S. nigrum var. humile produced the greatest increase in the amount of extracted Cd per plant. Furthermore, the S. diphyllum monoculture resulted in the highest amount of Cd extracted per pot, which may be useful for improving the ability of hyperaccumulators to decontaminate Cd-polluted environments.