Root system responses of hyperaccumulator Solanum nigrum L. to Cd

Though phytoremediation is an important technology for remedying heavy metal-contaminated soils, hyperaccumulation mechanism, especially in root, is still less known. Pot culture experiment was used to explore the tolerance mechanism of a cadmium (Cd) hyperaccumulator Solanum nigrum L. by determining the main root traits compared to the non-hyperaccumulator Solanum melongena L. (cultivar name Liaoqie 3) in the same plant family. The total root lengths, total root surface areas, and total root volumes of S. nigrum were not significantly decreased (p < 0.05) compared to their controls when Cd spikes were lower than 20 mg kg(-1). However, the abovementioned three factors of S. melongena were significantly decreased (p < 0.05) when 20 mg kg(-1) of Cd was spiked. By contrast, S. nigrum showed stronger tolerance to Cd. In addition, S. nigrum showed all Cd hyperaccumulator characteristics, i.e., a Cd hyperaccumulator. S. melongena was a non-Cd hyperaccumulator. These results indicated that root trait can be a factor of hyperaccumulation because of strong tolerance to Cd.