Role of the Ca-pectates on the accumulation of heavy metals in the root apoplasm.
In order to better understand the processes that regulate the accumulation in the apoplasm of heavy metals and their mobilization by the plant metabolites it is essential to study the mechanisms that regulate the interactions between metal ions and pectins. In such a context, the sorption of Cd(II), Zn(II), Cu(II) and Pb(II) from single and multi-metal solutions, by a Ca-polygalacturonate gel with a degree of esterification of 18.0 (PGAM(1)) and 65.5% (PGAM(2)) was studied in the 3.0-6.0 pH range in the presence of CaCl(2) 2.5mM. The sorption of Cr(III) from single metal solution was also considered. The results show that the amount of each metal ion sorbed increases with increasing the initial metal ion concentration and pH. The data from the single metal solution tests show that at pH 6.0 the affinity of the metal ions towards the PGAM(1) matrix follows the order: Cr(III)>Cu(II)≅Pb(II)≫Zn(II)≅Cd(II). The simultaneous sorption of the bivalent metal ions by the PGAM(1) gels indicates that Pb(II) is selectively sorbed. The FT-IR spectra show that the carboxylate groups are mainly responsible for the metal ion coordination. The ability of PGAM(2) to accumulate Cr(III), Cu(II), and Pb(II) was lower than that found in the PGAM(1) systems whereas the sorption of Zn(II) and Cd(II) was negligible.
Castaldi
Paola
P
Dipartimento di Scienze Ambientali Agrarie e Biotecnologie Agroalimentari, Università di Sassari, V.le Italia 39, 07100 Sassari, Italy.
Lauro
Giampaolo
G
Senette
Caterina
C
Deiana
Salvatore
S
D002118:Calcium / Q000378:metabolism; D002412:Cations / Q000493:pharmacokinetics; D005782:Gels; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000493:pharmacokinetics*; D010368:Pectins / Q000378:metabolism / Q000493:pharmacokinetics*; D018517:Plant Roots / Q000737:chemistry / Q000378:metabolism*; D012996:Solutions
D002412:Cations; D005782:Gels; D019216:Metals, Heavy; D012996:Solutions; D010368:Pectins; D002118:Calcium; C003181:polygalacturonic acid