Characterization of Cadmium Binding, Uptake, and Translocation in Intact Seedlings of Bread and Durum Wheat Cultivars

Jonathan J. Hart^*, Ross M. Welch, Wendell A. Norvell, Lori A. Sullivan¹, and Leon V. Kochian

United States Plant, Soil, and Nutrition Laboratory, United States Department of Agriculture, Agricultural Research Service, Cornell University, Ithaca, New York 14853

High Cd content in durum wheat (Triticum turgidum L. var durum) grain grown in the United States and Canada presents potential health and economic problems for consumers and growers. In an effort to understand the biological processes that result in excess Cd accumulation, root Cd uptake and xylem translocation to shoots in seedlings of bread wheat (Triticum aestivum L.) and durum wheat cultivars were studied. Whole-plant Cd accumulation was somewhat greater in the bread wheat cultivar, but this was probably because of increased apoplastic Cd binding. Concentration-dependent ¹⁰⁹Cd²⁺-influx kinetics in both cultivars were characterized by smooth, nonsaturating curves that could be dissected into linear and saturable components. The saturable component likely represented carrier-mediated Cd influx across root-cell plasma membranes (Michaelis constant, 20-40 nm; maximum initial velocity, 26-29 nmol g¹ fresh weight h¹), whereas linear Cd uptake represented cell wall binding of ¹⁰⁹Cd. Cd translocation to shoots was greater in the bread wheat cultivar than in the durum cultivar because a larger proportion of root-absorbed Cd moved to shoots. Our results indicate that excess Cd accumulation in durum wheat grain is not correlated with seedling-root influx rates or root-to-shoot translocation, but may be related to phloem-mediated Cd transport to the grain.

Plant Physiol. (1998) 116: 1413-1420
Copyright Clearance Center:   0032-0889/98/116/1413/08
© 1998 American Society of Plant Physiologists

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