A newly-discovered Cd-hyperaccumulator Solanum nigrum L.

A systematic investigation was conducted to screen for cadmium-hyperaccumulator from 54 species in 20 weed families using outdoor pot-culture experiment and small-scale field experiment. The results from the outdoor pot-culture experiment showed that Cd concentrations in the stems and leaves of Solanum nigrum L. growing in a soil spiked with 25 mg/kg Cd were up to 103.8 and 124.6 mg/kg (DW), respectively, which was greater than 100 mg/kg, minimum Cd concentration for a Cd-hyperaccumulator. The Cdenrichment factor(EF,concentration ratio in plant to soil) in shoots was as high as 2.68. Moreover, Cd accumulation in shoots was greater than that in roots (TF, concentration ratio in shoots to roots) and the plant biomass growth was not inhibited at the Cd concentrations tested compared with the control. The results of the small-scale field experiment also showed that the characteristics of Cd accumulation in S. nigrum were all consistent with the characteristics of Cd-hyperaccumulators. Thus S. nigrum can be classified as a Cd-hyperaccumulator. This work is important for further research in the areas of hyperaccumulators screening, and plant-tolerance physiology and evolution. It provides a pat- entable new plant species for phytoremediation of Cd-con- taminated soils.

Viola baoshanensis,a plant that hyperaccumulates cadmium

This paper reports upon the finding of Viola baoshanensis, a cadmium (Cd) hyperaccumulator through field survey and greenhouse experiments. Average Cd concentration in the shoots and roots of V. baoshanensis growing on Baoshan lead/zinc mine in Hunan Province, China, was 1168 and 981 mg/kg, respectively, varying from 456 to 2310mg/kg in the shoots, and from 233 to 1846 mg/kg in the roots.The ratio of Cd concentration in shoot to root (DW) and that in plant shoots to total concentration in surface soil was 1.32 and 2.38, respectively. Under nutrient solution culture, biomass (DW) of V. baoshanensis exposed to 0-30 mg/L Cd insolution increased with Cd supply increasing and reached a maximum at 30 mg/L Cd. Further increase of Cd concentration (40, 50 mg/L) in solution significantly reduced biomass.Cd concentration in the shoots was positively correlated with Cd concentration in the culture medium. Cd concentration in the shoots reached 4825 mg/kg at 50 mg/L Cd solution. Theratio of Cd concentration of shoots to roots in V. baoshanensis was greater than 1 at all Cd treatments, with an average of 1.67 (1.14-2.22). The results indicate that V. baoshanensis is a Cd hyperaccumulator plant.

Subcellular distribution and compartmentalization of arsenic in Pteris vittata L.

The subcellular distribution of arsenic (As) in Pteris vittata L., an As-hyperaccumulator, was studied to de- termine As compartmentalization and to explore the mecha- nisms that confer As tolerance. When the plant was grown in a nutrient solution without additional As, most of the accu- mulated As was isolated to the cell wall. However, in plants growing in a nutrient solution containing 0.1 or 0.2 mmol/L As, approximately 78% of the total As accumulated within the pinna. The proportions of As accumulation in the cyto- plasmic supernatant fraction were 78% of that in the pinna and 61% of that in the plant. In either treatment group (0.1 or 0.2 mmol/L As), the fraction containing the lowest level of As was the organelle fraction. These results suggest that As accumulates in the pinna where it is primarily distributed in the cytoplasmic supernatant fraction. The role of As com- partmentalization may be intricately linked with As detoxi- fication in P. vittata L.

Cellular distribution of arsenic and other elements in hyperaccumulator Pteris nervosa and their relations to arsenic accumulation

Synchrotron radiation X-ray fluorescence spectroscopy (SRXRF) was used to study the cellular distri- butions of arsenic and other elements in root, petiole, pinna of a newly discovered arsenic hyperaccumulator, Pteris nervosa. It was shown that there was a trend in P. nervosa to transport arsenic from cortex tissue to vascular tissue in root, and keep arsenic in vascular during transportation in petiole, and transport arsenic from vascular tissue to adaxial cortex tissues in midrib of pinnae. More arsenic was accumulated in mesophyll than in epidermis in pinnae. The distributions of some elements, such as K, Ca, Mn, Fe, Cu, Zn, in petiole, midrib and pinna were similar to that of arsenic, indicating that those cations might cooperate with arsenic in those transportation processes; whereas the distributions of Cl and Br in pinna were the reverse of that of arsenic, indicating that those anions might compete with arsenic in pinna of P. nervosa.