Tolerant mechanisms of Rorippa globosa (Turcz.) Thell. hyperaccumulating Cd explored from root morphology

Hoagland solution was used to determine the root morphology properties of Rorippa globosa (Turcz.) Thell. and Rorippa palustris (Leyss.) Bess. Under the conditions of Cd spiked at 2.5 and 5 mg kg(-1), R. globosa showed all hyperaccumulative characteristics and was a Cd-hyperaccumulator. In contrast, R. palustris was a non-hyperaccumulator. The total root lengths, total root surface areas and total root volumes of R. globosa were not significantly decreased (p<0.05) compared to the control when 2.5 and 5 mg kg(-1) of Cd added. However, these 3 indexes of R. palustris were all significantly decreased (p<0.05) when 2.5, 5, 10, 20 and 40 mg kg(-1) Cd added compared its control. The average root diameters of R. palustris and R. globosa were not affected by Cd. These results showed that root morphology might be a factor of plant with strong tolerance to Cd.