Cadmium uptake and translocation in seedlings of near isogenic lines of durum wheat that differ in grain cadmium accumulation

Abstract Background Cadmium (Cd) concentrations in durum wheat ( Triticum turgidum L. var durum ) grain grown in North American prairie soils often exceed proposed international trade standards. To understand the physiological processes responsible for elevated Cd accumulation in shoots and grain, Cd uptake and translocation were studied in seedlings of a pair of near-isogenic durum wheat lines, high and low for Cd accumulation in grain. Results In short-term studies (<3 h) using 109 Cd-labelled nutrient solutions, there were no differences between lines in time- or concentration-dependent 109 Cd accumulation by roots. In contrast, rates of 109 Cd translocation from roots to shoots following longer exposure (48–60 h) were 1.8-fold higher in the high Cd-accumulating line, despite equal whole-plant 109 Cd accumulation in the lines. Over the same period, the 109 Cd concentration in root-pressure xylem exudates was 1.7 to 1.9-fold higher in the high Cd-accumulating line. There were no differences between the lines in 65 Zn accumulation or partitioning that could account for the difference between lines in 109 Cd translocation. Conclusion These results suggest that restricted root-to-shoot Cd translocation may limit Cd accumulation in durum wheat grain by directly controlling Cd translocation from roots during grain filling, or by controlling the size of shoot Cd pools that can be remobilised to the grain.