Uptake of zinc from chelate-buffered nutrient solutions by wheat genotypes differing in zinc efficiency

Abstract

Zinc-efficient Triticum aestivum (cv. Warigal) and Zn-inefficient Triticum turgidum conv. durum (cv. Durati) were grown in chelate-buffered, complete nutrient solutions providing either deficient or sufficient Zn supply. When transferred to fresh chelatebuffered nutrient solutions containing a wide range of Zn supplies (0–1.28 μmol m⁻³ Zn²⁺ activity) for 24–48 h, both genotypes increased net Zn uptake linearly with an increase in solution Zn²⁺ activities. Zincefficient Warigal accumulated Zn at a greater rate than Zn-inefficient Durati. The greater rate of net Zn uptake was observed by plants of both genotypes when pretreated at deficient Zn supply. Net loss of Zn to the solution was higher in plants pretreated with sufficient Zn and was inversely related to Zn²⁺ activity in the external solution. When continuously supplied with 40 nmol m⁻³ Zn²⁺, net Zn uptake by Zn-efficient Warigal was significantly greater than that of Zn-inefficient Durati, but the difference diminished with plant age. Shoot concentrations of Fe, Mn and Cu were higher when plants were grown at deficient than at sufficient Zn supply. The Zn-efficient genotype transported less Zn and Fe to shoots and had higher Fe concentrations in roots than the Zn-inefficient genotype, supporting the hypothesis that Zn efficiency may be connected with inefficient transport of Fe from roots to shoots and thus initiation of the Fe-deficiency response resulting in increased release of Zn- and Fe-binding phytosiderophores. It is concluded that differential Zn efficiency of wheat genotypes is at least partly due to a greater ability of efficient genotypes to accumulate Zn.