Identification of nickel chelators in three hyperaccumulating plants: An X-ray spectroscopic study

• Published in: Phytochemistry (Oxford) Vol. 69; no. 8; pp. 1695 - 1709
• Main Authors: Montargès-Pelletier, Emmanuelle, Chardot, Vanessa, Echevarria, Guillaume, Michot, Laurent J., Bauer, Allan, Morel, Jean-Louis
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 01.05.2008; Elsevier
• Subjects: Alyssum murale; analysis; Biological and medical sciences; Brassicaceae; Brassicaceae - chemistry; Brassicaceae - metabolism; carboxylic acids; chelating agents; Chelating Agents - chemistry; Chelating Agents - metabolism; Chelation; Chemical constitution; chemistry; Citrate; citric acid; Citric Acid - analysis; Citric Acid - chemistry; Fundamental and applied biological sciences. Psychology; Glutamic Acid; Glutamic Acid - analysis; Glutamic Acid - chemistry; heavy metals; Hyperaccumulating plants; hyperaccumulators; Leptoplax emarginata; Life Sciences; Ligands; Malate; Malates; Malates - analysis; Malates - chemistry; malic acid; Metabolism; Metabolism. Physicochemical requirements; Molecular Structure; Nickel; Nickel - chemistry; Nickel - metabolism; Noccaea caerulescens; Phytopathology and phytopharmacy; phytoremediation; Plant physiology and development; soil pollution; spectral analysis; Spectrophotometry; Storage; Thlaspi; Thlaspi - chemistry; Thlaspi - metabolism; Thlaspi caerulescens; Vegetal Biology; X-Rays; Storage; Hyperaccumulating plants; Malate; Leptoplax emarginata; Alyssum murale; Chelation; Citrate; Thlaspi caerulescens; Nickel; Molecular structure; Organic acids; Stem; Absorption; Histidine; Cruciferae; Carboxylic acid; Dicotyledones; Angiospermae; Speciation; Thlaspi; Root; Plant leaf; Complexes; Spermatophyta; Aqueous solution; nickel; thlaspi caerulescens; malate; citrate; chelation; hyperaccumulating plants; leptolax emarginata; storage; alyssum murale
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/j.phytochem.2008.02.009

Hyperaccumulators Thlaspi caerulescens, Alyssum murale and Leptoplax emarginata were grown in rhizoboxes, on soil enriched with nickel bearing smectite. A direct investigation method demonstrated that nickel cations were majoritarily stored within leaves as Ni(malate) complexes whereas Ni(citrate) complexes could be revealed within stems of L. emarginata. We have investigated the accumulation of nickel in a hyperaccumulating plant from the Brassicacae family Leptoplax emarginata (Boiss.) O.E. Schulz. Two supplementary hyperaccumulating plants, which have been the subject of a high number of publications, Alyssum murale Waldst. & Kit and Thlaspi caerulescens J.&C. Presl, and a nonaccumulating species Aurinia saxatilis were also studied for reference. The plants were grown during 4 months in specific rhizoboxes with Ni-bearing minerals as a source of nickel. Nickel speciation was analyzed through X-ray absorption spectroscopy at Ni K-edge (X-ray absorption near edge spectroscopy and extended X-ray absorption fine structure spectroscopy) in the different parts of the plants (leaves, stems and roots) and compared with aqueous solutions containing different organo-Ni(II) complexes. Carboxylic acids (citrate, malate) appeared as the main ligands responsible of nickel transfer within those plants. Citrate was found as the predominant ligand for Ni in stems of Leptoplax and Alyssum, whereas in leaves of the three plants, malate appeared as the chelating organic acid of accumulated metal. Histidine could not be detected either in leaves, stems nor roots of any studied plant sample.