No abstract

Summary  This work evaluated the influence of iron deficiency and phytosiderophore exudation on the acquisition of copper by two bread wheat (Triticum aestivum) genotypes (‘Aroona’ and ‘Songlen’) grown in a calcareous vineyard soil, which had been contaminated by repeated applications of copper fungicides.  A pot experiment was designed with a cropping device that enabled an easy access to shoots, roots and rhizosphere soil. Before being placed in contact with the soil, wheat seedlings had been subjected to, or not subjected to, either zinc or iron starvation, in order to stimulate the release of phytosiderophores.  Under zinc starvation, the zinc‐efficient genotype (‘Aroona’) acquired more soil copper. By contrast, iron starvation resulted in an enhanced release of phytosiderophores in both genotypes (before being grown on the soil), in elevated copper concentrations in shoots and roots and in a significantly increased acquisition of copper by wheat.  Iron deficiency thus resulted in elevated acquisition of copper from the copper‐contaminated soil, possibly through enhanced phytosiderophore release. Phytotoxic concentrations were, however, not attained in wheat shoots, as a major proportion of acquired copper accumulated in the roots.

No abstract

This work aimed at defining the optimal conditions for a novel ecotoxicological test designed for evaluating the bioavailability and phytotoxicity of metals to plants. This biotest, which provided easy access to roots, shoots, and rhizosphere soil, was applied to a vineyard calcareous soil that had been contaminated by the application of Cu fungicides. A preliminary hydroponic experiment comparing various levels of solution Cu concentration enabled us to determine the no observable adverse effects concentration (NOAEC), which was in the range 5 to 20 microM total Cu (0.01-0.06 microM free Cu ion) for rape (Brassica napus L. cv. Goeland). For the biotest, rape was grown in hydroponic conditions for 21 d in pots designed so that plants developed a planar mat of roots at the surface of a polyamide mesh. By then, the plants were transferred for 4 or 8 d onto a 1- or 3-mm-thick soil layer that was separated from the root mat by the mesh and connected to a reservoir of nutrient solution or deionized water via a filter paper wick. An 8-d period was the best option as it enabled plant growth to be significant. The use of 1-mm soil thickness was recommended if the biotest aimed at investigating root-induced changes in the rhizosphere. Although it may cause some artifacts, compared with deionized water, nutrient solution provided better standardized conditions for comparing widely differing soil samples. The studied soil did not induce any Cu phytotoxicity in spite of its fairly large total Cu content.