Summary• Here, Thlaspi caerulescens populations from contrasting soil types (serpentine, calamine and nonmetalliferous) were characterized with regard to tolerance, uptake and translocation of zinc (Zn), cadmium (Cd) and nickel (Ni) in hydroponic culture.• Results showed that high-level tolerances were apparently metal-specific and confined to the metals that were enriched at toxic levels in the soil at the population site.• With regard to metal accumulation, results suggested that, unlike Zn hyperaccumulation, Cd and Ni hyperaccumulation were not constitutive at the species level in T. caerulescens .• In general, the populations under study exhibited a pronounced uncorrelated and metal-specific variation in uptake, root to shoot translocation, and tolerance of Zn, Cd and Ni. The distinct intraspecific variation of these characters provides excellent opportunities for further genetic and physiological dissection of the hyperaccumulation trait.
Naturally occurring genetic variation for contents of cationic minerals in seeds of Arabidopsis thaliana was studied by screening a series of accessions (ecotypes) for Ca, Fe, K, Mg, Mn, Na, Zn, and for total contents of P. Variation was observed for all minerals and correlations between contents of various minerals were present, most noticeably between Ca and Mg, P and Mg, and P and Mn. The genetic basis of this variation was further studied by QTL analysis, using the Landsberg erecta (L er ) ¥ ¥ ¥ ¥ Cape Verde Islands (Cvi) recombinant inbred population. For all minerals, except Na, one or more QTL were detected, explaining up to 78% of the variation. The map positions of several QTL were confirmed by analysis of near isogenic lines, carrying small Cvi introgressions in L er background. Interesting co-locations of QTL suggest pleiotropic effects, due to physiological coupling of the accumulation of certain minerals or to linkage of different genes. By comparing the map positions of QTL with the positions of genes expected to play a role in cation translocation, several candidate genes are suggested.
Increased resistance to copper-induced damage ofthe root cell plasmalemma in copper tolerant Silene cucubalus. -Physiol, Plant, 82: 523-528.The relation hetween copper tolerance and the sensitivity of plants with respect to the effect of copper on the plasmalemma of root cells was studied using plants from one copper sensitive and two copper tolerant populations of Silene cucubalus Wib. In each population, the external copper concentration needed to induce ion leakage (a measure of damage to the permeability barrier) was. similar to the highest no-effectconcentration of copper for root growth in that population. At higher concentrations, the degree of root growth inhibition paralleled the rate of ion leakage, the degree of trypan blue staining (a measure of plasmalemma integrity) and the accumulation of lipid peroxidation products. The amount of copper taken up by the plants was inversely related to their levd of copper tolerance. Compared to copper sensitive plants, copper tolerant plants showed no increased resistance to either the sulfhydryl reagent N-ethylmaleimide or the free radical-producing compound cumene hydroperoxide.These results indicate that damage to the permeability barrier of root cells constitutes the primary effect of copper toxicity in both sensitive and tolerant plants, and that copper tolerance is coupled to the ability of the plants to prevent such damage. This ability might depend on exclusion of copper by the root cell plasmalemma.
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