Abstract
BackgroundCadmium (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.ResultsIn short-term studies (<3 h) using 109Cd-labelled nutrient solutions, there were no differences between lines in time- or concentration-dependent 109Cd accumulation by roots. In contrast, rates of 109Cd 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 109Cd accumulation in the lines. Over the same period, the 109Cd 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 65Zn accumulation or partitioning that could account for the difference between lines in 109Cd translocation.ConclusionThese 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.
Highlights
Cadmium (Cd) concentrations in durum wheat (Triticum turgidum L. var durum) grain grown in North American prairie soils often exceed proposed international trade standards
The results of our current study show that genotypic variation in rootto-shoot Cd translocation alone accounts for the difference between isolines in shoot Cd accumulation
There were no differences between isolines in Cd uptake by roots (Figure 1, 2, 3) or whole-plants (Figure 6B) that could account for the difference in root-to-shoot Cd translocation
Summary
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. Cadmium (Cd) tends to accumulate in grain crops grown in North American prairie soils with naturally elevated Cd availability [1,2]. Cadmium accumulation in grain of high- and low-accumulating near-isogenic lines was correlated with Cd accumulation in the leaves of the seedlings under field conditions [2]. This suggests that differences in Cd accumulation in the vegetative phase may be important determinants of Cd accumulation in grain, or at least be indicative of Cd transport to grain (page number not for citation purposes)
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