Iron plaque on roots of Aster tripolium L.: interaction with zinc uptake

Abstract

SUMMARY1 he iron plaque on roots of Aster tripolium L. growing in waterlogged salt marsh soil adsorbed appreciable amounts of Zn and Cu,with maximum Zn/Fe and Cu/Fe ratios of 0-1. When concentrations of Zn or Cu adsorbed 'n the iron plaque are expressed as mg metal kg"' FeOOH (assuming that iron plaque consists mainly of I'eOOH), the Zn and Cu concentrations ot the iron plaque was up to 680 and up to 2900 times higher than in the surrounding sediment, respectively. The Zn concentration in red roots (with iron plaque) was higher than in white roots (without iron plaque), Zn concentrations in field sampled roots were correlated with the amount of Zn on "le roots and the Zn concentration in the soil, whereas Cu concentrations in the roots were only significantly correlated to the Cu concentration in the soil. In vitro experiments showed that red roots take up more Zn than •white roots. Measurement of Zn uptake by excised roots showed that the uptake of Zn into the xylem fluid was significantly higher in roots with 500-2000 nmol Fe cm"'' on the root surface compared to roots with less than 500 Or more than 2000 nmol Fe cm"'^ on the root surface. The results indicate that iron plaque enhances uptake of Zn ny the roots but may act as a barrier when large amounts of Fe are deposited on the root surface. The role of the "•on plaque on roots of salt marsh plants growing in soil contaminated with heavy metals is discussed

Copper and nickel uptake, accumulation and tolerance in Typha latifolia with and without iron plaque on the root surface

“…It has not been accepted that iron plaque acts entirely as an external barrier to toxic metals; it might influence tolerance in other ways, such as leading to a higher concentration of 'active iron' within leaves (Greipsson, 1995), as well as absorbing and immobilizing metals. Although the relationship between iron plaque on roots and metal absorption and accumulation by plants has been studied in recent years , 1990Greipsson & Crowder, 1992;Otte et al, 1989Otte et al, , 1991St-Cyr, Fortin & Campbell, 1993;Greipsson, 1994), this relationship is still unclear. Typha latifolia L. is a common and productive wetland plant of world-wide geographical distribution.…”

“…Recently, with reference to the 1994; Smolders & Roelofs, 1996). Field observations oxidation state of Fe in root plaque, Wang & Peverly have also shown that wetland plants capable of (1996) indicated that iron plaque on the roots of surviving in metal-contaminated soils frequently possess iron plaque on their roots (Taylor et al, 1984;Conlin & Crowder, 1989;Otte et al, 1989, * To whom correspondence should be addressed.…”

“…of wetland plants are known to form so-called iron Tolerance of wetland plants to high ferrous iron plaque on their roots by oxidizing Fe^"^ to Fe^"^ concentrations is associated with oxidation in the resulting from the oxidizing activity of the plant rhizosphere (Bartlett, 1961;Green & Ftherington, roots and associated micro-organisms (Chen, Dixon 1977;Johnson-Green & Crowder, 1991;Wang & & Turner, 1980;Mendelssohn & Postek, 1982;Peverly, 1996). Oxidation in the rhizosphere might Taylor, Crowder & Rodden, 1984;McLaughlin, van also diminish the toxicity of other reduced subLoon & Crowder, 1985;Conlin & Crowder, 1989; stances such as Mn^+ and S'^" (Armstrong, 1967;Otte et al, 1989;St-Cyr & Crowder, 1990;Crowder Chen et al, 1980;Armstrong, Brandle & Jackson, & St-Cyr, 1991). Recently, with reference to the 1994; Smolders & Roelofs, 1996).…”

Influence of external zinc and phosphorus supply on Cd uptake by rice (Oryza sativa L.) seedlings with root surface iron plaque

“…Since P and Zn are essential elements for plant growth under our experimental conditions in which P and Zn concentrations were not high but shoot Cd concentrations were high, rice may have evolved mechanisms to increase plant uptake and translocation of Zn and P. For example, Zhang et al (1998) found that phytosiderophores released by Fedeficient plants enhanced Zn uptake by rice plants with iron plaque up to a particular amount of Fe, and enhanced shoot P uptake was assumed to be related to substances other than siderophores released by plants (Zhang et al 1999). The overall role of iron plaque in elemental uptake by rice may vary among studies according to differences in culture methodology, duration of the treatments, the element or contaminant studied, or the amount of iron plaque on the root surfaces (Zhang et al 1998;Otte et al 1989), plant genotypes (Liu et al 2004a) and to the status of nutrients such as P (Liu et al 2004b) and Fe (Zhang et al 1998). The present study and others highlight the complexity of transport of nutrient elements and/ or metal(loids) from soil to rice shoots via the soilrhizosphere-iron plaque-root-shoot circuit.…”

“…Iron plaque on fresh root surfaces was extracted using a modified dithionite-citrate-bicarbonate (DCB) method (Taylor and Crowder 1983;Otte et al 1989). Briefly, the entire root system of each seedling was incubated for 60 min at 25°C in 60 ml 0.03 mol l −1 sodium citrate (Na 3 C 6 H 5 O 7 · 2H 2 O) and 0.125 mol l −1 sodium bicarbonate (NaHCO 3 ) with the addition of 1.2 g sodium dithionite (Na 2 S 2 O 4 ).…”