Submitted to: International Symposium on Biogeochemistry of Trace Elements Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/11/2011
Publication Date: 7/14/2011
Citation: Centofanti, T., Sayers, Z., Cabello-Conejo, M.I., Broadhurst, L.E., Kidd, P.S., Davis, A.P., Sicher Jr, R.C., Chaney, R.L. 2011. Organic acids rather than histidine predominate in Ni chelation in Alyssum hyperaccumulator xylem exudate. International Symposium on Biogeochemistry of Trace Elements Proceedings. On disk. Interpretive Summary: .
Technical Abstract: A better understanding of Ni uptake mechanisms by hyperaccumulator plants is necessary to improve Ni uptake efficiency for phytoremediation technologies i.e. phytomining. It is known that an important aspect of Ni translocation involves Ni chelation with organic ligands. However, it is still not clear which specific ligands are involved. We have collected xylem sap of 100 days old plants of A. corsicum, A. montanum and A. pintodasilvae grown on: a) serpentine soil, b) Promix spiked with six Ni levels, c) nutrient solutions with three Ni levels. Xylem sap was collected using a pressure chamber for 1 hour. Total Ni concentration in xylem sap, shoots and roots and the concentration of 17 amino acids and 9 organic acids in the xylem sap were measured. We have found µM levels of amino acids and Ni in xylem sap which is three orders of magnitude lower than the levels reported in previous studies. In A. corsicum histidine increased with increased Ni level but in A. pintodasilvae it decreased. The increase in Ni concentration did not cause any significant increase in histidine relative to the other amino acids measured. Malate and citrate levels were the highest relative to the other organic acids and their level is similar or higher than histidine. Over the range of Ni treatments in hydroponics, there was a good correlation between Ni and malate in xylem sap of A. corsicum (r=0.7) and a lower correlation between Ni and citrate (r=0.5) whereas there was no correlation between histidine and Ni (r=-0.07). In this study a different approach for xylem sap collection when plants reached a steady-state of Ni uptake was used and the results showed that organic acids rather than histidine predominate in the chelation and xylem transport of Ni.