ARS | Publication request: CADMIUM PARTITIONING AND PHYTOCHELATIN RESPONSE IN NEAR ISOGENIC LINES OF DURUM WHEAT THAT DIFFER IN GRAIN CADMIUM ACCUMULATION

Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 1, 1999
Publication Date: N/A

Technical Abstract: Durum wheat grown in cadmium-containing soils of the North American Great Plains region can accumulate Cd to levels that exceed proposed international trade standards. Understanding the physiological basis for excess Cd accumulation in durum wheat is therefore an important goal. Paired near-isogenic lines of durum wheat that differ two to three-fold in grain Cd accumulation have been developed. These isolines offer an experimental system for examining the physiological effects of a single gene or a small complement of genes. A pair of isolines grown in solution culture in a growth chamber was used to study Cd distribution among plant organs and phytochelatin concentrations in roots. Previous experiments have shown that root Cd uptake kinetics are similar in the two isolines, but that partitioning between root and shoot is different. The low grain Cd-accumulating isoline retained more Cd in the root than the high grain Cd-accumulating isoline, which exhibited higher Cd concentrations in all above-ground parts. Analysis of root homogenates showed that the low Cd-accumulating isoline had higher constitutive levels of phytochelatins, and that phytochelatin concentration increased upon exposure to Cd in nutrient solution. Phytochelatins are known to have a high binding affinity for Cd and the phytochelatin-Cd complex has been shown to be transported across the tonoplast of plant root cells. We propose, therefore, that the low Cd-accumulation trait is related to differential synthesis of phytochelatins and/or sequestration of the phytochelatin-Cd complex in the vacuole of durum.