Indian mustard, Brassica juncea, is known to take up and hyperaccumulate several toxic heavy metals, including cadmium. This feature makes the species a useful tool for phytoremediation, a technique which uses plants to extract toxic substances from contaminated soil or water. Cadmium uptake by hydroponically-grown specimens fof Indian mustard was studied in solutions with and without calcium ion present in the growth medium. Plants were studied under conditions of (a) no added chelating agents, and (b) with enhancement of uptake by ethylenediaminetetraacetic acid (EDTA) and three other related chelating agents: EGTA, DPTA, and CDTA. The interactive effect of competition or enhancement of uptake on metal accumulation was also investigated and assessed in terms of possible membrane transport mechanisms. Samples were analyzed for calcium and cadmium content using flame atomic absorption spectrophotometry. Of the synthetic chelating agents used, EDTA was most effective at increasing cadmium uptake (by 46% relative to control), compared to 37% for EGTA, 30% for CDTA, and 4.6% for DPTA. In a further study, plants grown in nutrient solution without calcium exhibited decreased cadmium accumulation by 52% compared to controls with calcium but without EDTA. This result was somewhat unexpected and may suggest implications for the role of calcium in active membrane transport channels for cadmium. Additional research investigated the effect of varying levels of calcium on cadmium uptake with and without EDTA, but results were inconclusive. Future experiments will repeat the studies done at varying calcium levels.
Boyd, J. S. (2005). Interactions Between Cadmium and Calcium Ions in the Chelate-mediated Metal Uptake of Indian Mustard, Brassica Juncea (Undergraduate honors thesis, University of Redlands). Retrieved from http://inspire.redlands.edu/cas_honors/119