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

Abstract

Durum wheat (Triticum turgidum L. var durum) cultivars exhibit lower Zn efficiency than comparable bread wheat (Triticum aestivum L.) cultivars. To understand the physiological mechanism(s) that confers Zn efficiency, this study used 65 Zn to investigate ionic Zn 2؉ root uptake, binding, and translocation to shoots in seedlings of bread and durum wheat cultivars. Time-dependent Zn 2؉ accumulation during 90 min was greater in roots of the bread wheat cultivar. Zn 2؉ cell wall binding was not different in the two cultivars. In each cultivar, concentration-dependent Zn 2؉ influx was characterized by a smooth, saturating curve, suggesting a carriermediated uptake system. At very low solution Zn 2؉ activities, Zn 2؉ uptake rates were higher in the bread wheat cultivar. As a result, the Michaelis constant for Zn 2؉ uptake was lower in the bread wheat cultivar (2.3 M) than in the durum wheat cultivar (3.9 M). Low temperature decreased the rate of Zn 2؉ influx, suggesting that metabolism plays a role in Zn 2؉ uptake. Ca inhibited Zn 2؉ uptake equally in both cultivars. Translocation of Zn to shoots was greater in the bread wheat cultivar, reflecting the higher root uptake rates. The study suggests that lower root Zn 2؉ uptake rates may contribute to reduced Zn efficiency in durum wheat varieties under Zn-limiting conditions.

Effects of zinc activity in nutrient solution on uptake, translocation, and root export of cadmium and zinc in three wheat genotypes with different zinc efficiencies

“…Our results suggest that the Cd uptake system in Zn-efficient genotypes is different from that in the Zn-inefficient genotypes (Oliver et al 1995;Hart et al 1998). The nature of Cd uptake saturability may be different among wheat genotypes.…”

Differential Capacity for High-Affinity Manganese Uptake Contributes to Differences between Barley Genotypes in Tolerance to Low Manganese Availability

“…Mn to cell walls during the influx experiments was carried out following the procedure used for Zn 21 adsorption by and Hart et al (1998). This procedure is based on subtraction of the linearly increasing part of the influx curve, which may be due to adsorption, from the total uptake curve, reflecting true uptake into the cells, the saturable component (Figs.…”

“…3). Following and Hart et al (1998), the kinetics of root 54 Mn 21 was graphically resolved into saturable and linear components, respectively (Figs. 3,B and C,and 4,B and C), where the latter describes Mn absorbed to cell walls.…”

Diffusion limitation of zinc fluxes into wheat roots, PLM and DGT devices in the presence of organic ligands

“…[12] EDTA is a very strong ligand for Zn, often used as a ligand to buffer Zn 2þ concentrations in solution as its complexes are expected to contribute only a very small extent to Zn uptake. [12][13][14] Interestingly, histidine increased Zn uptake ,3 times more than citrate, although histidine has a higher binding strength for Zn than citrate. An important difference between Zn complexes with citrate and histidine is that citrate complexes are negatively charged at neutral pH, whereas histidine complexes are mainly neutral and to a minor extent even positively charged at pH 7, according to thermodynamic speciation calculations (using MINEQL).…”