|Hacisalihoglu, Gokhan - CORNELL UNIVERSITY|
|Hart, Jonathan - CORNELL UNIVERSITY|
Submitted to: Plant Physiology
Publication Type: Abstract Only
Publication Acceptance Date: June 23, 2000
Publication Date: N/A
Technical Abstract: Zn deficiency is a serious agricultural problem that causes dramatic reductions in crop yield and quality on as much as 30% of the world's arable lands. Plant genotypes differ in their tolerance to Zn deficiency stress, and this trait is known as zinc efficiency (ZE). Although mechanisms of zinc efficiency have not been clearly elucidated, numerous factors could contribute to ZE including Zn uptake, compartmentalization and utilization efficiency. In this study, the concentration-dependent kinetics of root Zn uptake were investigated in two wheat (Triticum aestivum L.) genotypes differing in zinc efficiency: Dagdas (efficient) and BDME (inefficient). Plants were grown hydroponically for 10 d in chelate-buffered solutions where the Zn2+ activity was controlled at Zn deficient (0.05 pM) or sufficient (147 pM) levels. Subsequently, roots of the intact seedlings were used for determination of unidirectional 65Zn2+ influx over a range of Zn2+ activities that spanned the high affinity (1 - 200 nM) and lower affinity (0 - 80 mM) uptake ranges. Analysis of the concentration dependent kinetics for root Zn2+ influx showed that both genotypes had similar rates of root Zn uptake and root and shoot tissue Zn concentrations. These findings indicate there is no correlation between root Zn uptake and zinc efficiency. Further kinetic analysis revealed the existence of two separate transport systems for root Zn uptake: a high-affinity system operating at low Zn activities (Km 0.1 - 3.9 nM) and a low-affinity system operating at higher Zn activities (Km 0.9 - 7.5 mM). The importance of these transporters to Zn acquisition will be discussed, as well as speculation on other possible mechanisms contributing to Zn efficiency.