Differential accumulation of Cd in durum wheat cultivars: uptake and retranslocation as sources of variation

Abstract

Durum wheat (Triticum turgidum L. var. durum) accumulates Cd from the soil depending on various factors. When grown in hydroponic solution containing Cd (20 microg l(-1)), roots had higher tissue Cd concentrations than shoots or heads. Kyle (the higher grain-Cd accumulating cultivar) had lower root-Cd, and greater shoot-Cd and head-Cd concentrations than Arcola (the lower grain-Cd accumulating cultivar). These cultivar differences were greater at flowering and ripening than at tillering. Much of the root-Cd was lost between the flowering and ripening stages of development. Distribution of (106)Cd among plant parts, after a single 24 h feeding, demonstrated that root-to-shoot transfer of Cd in Arcola was similar to that of Kyle at tillering, but it had ceased at flowering in Arcola but not Kyle. None of the Cd in wheat heads at ripening originated from (106)Cd exposure in the previous 24 h, suggesting that grain-Cd is a function of total shoot accumulation. Both cultivars demonstrated basipetal translocation of Cd; Arcola at tillering translocated more Cd from shoots to roots than Kyle. The proportion of Cd(2+)/Cd(total) in the nutrient solution decreased with time, suggesting that plant activity altered the solution chemistry. The alteration probably resulted from either preferential depletion of solution Cd(2+) and/or addition of root exudates. Lower grain-Cd accumulation in Arcola possibly resulted from a combination of reduced root-to-shoot transfer of Cd at flowering, as well as enhanced shoot-to-root retranslocation of Cd, at least in younger plants. Plant-mediated changes in solution-Cd speciation did not play a role.

Production of organic acids and adsorption of Cd on roots of durum wheat (Triticum turgidum L. var. durum)

“…Hart et al (1998) and Chan and Hale (2004) also speculated that most of the root-Cd in durum wheat cultivars is restricted to the apoplast, and Cd was mostly associated with the cell wall in roots of N. tabacum and T.…”

“…The yet to be identified gene responsible for differential Cd-accumulation in durum wheat appears to code for a trait that affects retention of Cd in the root (Berkelaar and Hale 2000) and/or root to shoot translocation of Cd (Chan andHale 2004, Harris andTaylor 2004) as opposed to uptake of Cd into the root. While we know the trait for low Cd-accumulation in the grain is dominant (Clarke et al 1997b), and the gene is located on chromosome 5B (Knox et al 2009), the function of this gene is not known.…”

Effects of Ammonium Chloride Fertilizer and its Application Stage on Cadmium Concentrations in Wheat (Triticum aestivumL.) Grain

“…Thus, it is possible that Cl enhances the transfer of Cd from the root/shoot to the grain, in addition to increasing the solubility of soil Cd. Cd translocation from roots to shoots is considered to be important for the accumulation of Cd in wheat grain (Chan and Hale, 2004;Greger and Löfstedt, 2004;Harris and Taylor, 2004). Further studies are required to elucidate the mechanisms underlying the effects of Cl on grain Cd accumulation.…”

It takes an individual plant to raise a community: TRFLP analysis of the rhizosphere microbial community of two pairs of high- and low-metal-accumulating plants

“…The distribution of Cd in two cultivars (cv) of durum wheat (Triticum durum Desf. ), Arcola and Kyle, confirmed Kyle as a high-accumulator and Arcola as a low-accumulator (Chan and Hale, 2004). Similarly, Brassica juncea is an established metal high-accumulator, while B. napus is a low-accumulator (McGrath et al, 2001).…”

“…All pots were kept in a growth chamber maintained at 21°C and 60% RH with The relative Cd-accumulating ability of each plant species was confirmed following the modified US EPA (2000) method described in Akhter and Macfie (2012). The tissue Cd concentrations were consistent with the relative metal-accumulating abilities of these plants (Chan and Hale, 2004;McGrath et al, 2001). …”