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Hyperaccumulator Plants (hyperaccumulator + plant)
Selected AbstractsWithin and between population genetic variation for zinc accumulation in Arabidopsis halleriNEW PHYTOLOGIST, Issue 1 2002Mark R. Macnair Summary ,,Hyperaccumulator plants in the field show significant variation in the metal concentration in their aerial parts, but little is known of the causes of this variation. This paper investigates the role of soil zinc (Zn) concentration and genetic variation in causing between and within population variation in Zn accumulation in Arabidopsis halleri. ,,Seed from 17 populations of A. halleri collected in central Europe were grown under standard conditions at three external Zn concentrations and tested for Zn concentration in the leaves. ,,Between population variation was highest at low external zinc concentrations. At 10 µm Zn some plants had very low leaf Zn concentrations, and were indistinguishable from nonaccumulators. However, at higher Zn concentrations, all plants showed hyperaccumulation. There were no differences in the accumulating abilities of populations from sites with different degrees of contamination. ,,Heritability of accumulation, determined for individual families from three populations, was quite high (25,50%), indicating that selection for increased accumulating ability should be possible, although selection would be easier at low external Zn concentrations. The Zn concentration of field collected plants was affected partly by plant genotype but not by the total soil Zn around their roots. [source] Phytotoxicity and phytoaccumulation of trivalent and hexavalent chromium in brake fernENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2005Yi Su Abstract A recently recognized hyperaccumulator plant, Chinese brake fern (Pteris vittata), has been found to extract very high concentration of arsenic from arsenic-contaminated soil. Chromium usually is a coexisting contaminant with arsenic in most contaminated soils. The potential application of ferns for phytoremediation of chromium(III)- and chromium(VI)-contaminated soils and their phytotoxicity to ferns has not been studied before. In this study, chromium distribution and phytotoxicity at the plant and cellular levels of brake ferns were studied using chemical analyses and scanning electron microscopy. The results show a higher phytotoxicity of Cr from Cr(VI)-contaminated soil to Chinese brake fern than from Cr(III)-contaminated soil. Phytotoxicity symptoms included significant decreases both in fresh biomass weight and relative water content (RWC), and also in leaf chlorosis during the late stage of growing. At higher concentrations (500 mg/kg Cr[VI] and 1,000 mg/kg Cr[III] addition), plants showed reduction in the number of palisade and spongy parenchyma cells in leaves. Compared with other plant species reported for phytoremediation of Cr(VI)-contaminated soil, brake fern took up and accumulated significant amounts of Cr (up to 1,145 mg/kg in shoots and 5,717 mg/kg in roots) and did not die immediately from phytotoxicity. Our study suggests that Chinese brake fern is a potential candidate for phytoremediation of Cr(VI)-contaminated soils, even though plants showed severe phytotoxic symptoms at higher soil Cr concentrations. [source] High-nickel insects and nickel hyperaccumulator plants: A reviewINSECT SCIENCE, Issue 1 2009Robert S. Boyd Abstract Insects can vary greatly in whole-body elemental concentrations. Recent investigations of insects associated with Ni hyperaccumulator plants have identified insects with relatively elevated whole-body Ni levels. Evaluation of the limited data available indicates that a whole-body Ni concentration of 500 ,g Ni/g is exceptional: I propose that an insect species with a mean value of 500 ,g Ni/g or greater, in either larval/nymphal or adult stages, be considered a "high-Ni insect". Using the 500 ,g Ni/g criterion, 15 species of high-Ni insects have been identified to date from studies in Mpumalanga (South Africa), New Caledonia and California (USA). The highest mean Ni concentration reported is 3 500 ,g Ni/g for nymphs of a South African Stenoscepa species (Orthoptera: Pyrgomorphidae). The majority of high-Ni insects (66%) are heteropteran herbivores. Studies of high-Ni insect host preference indicate they are monophagous (or nearly so) on a particular Ni hyperaccumulator plant species. Much of the Ni in bodies of these insects is in their guts (up to 66%,75%), but elevated levels have also been found in Malpighian tubules, suggesting efficient elimination as one strategy for dealing with a high-Ni diet. Tissue levels of Ni are generally much lower than gut concentrations, but up to 1200 ,g Ni/g has been reported from exuviae, suggesting that molting may be another pathway of Ni elimination. One ecological function of the high Ni concentration of these insects may be to defend them against natural enemies, but to date only one experimental test has supported this "elemental defense" hypothesis. Community-level studies indicate that high-Ni insects mobilize Ni into food webs but that bioaccumulation of Ni does not occur at either plant-herbivore or herbivore-predator steps. Unsurprisingly, Ni bioaccumulation indices are greater for high-Ni insects compared to other insect species that feed on Ni hyperaccumulator plants. There is some evidence of Ni mobilization into food webs by insect visitors to flowers of Ni hyperaccumulator plants, but no high-Ni insect floral visitors have been reported. [source] Metal concentrations of insects associated with the South African Ni hyperaccumulator Berkheya coddii (Asteraceae)INSECT SCIENCE, Issue 2 2006ROBERT S. BOYD Abstract The high levels of some metals in metal hyperaccumulator plants may be transferred to insect associates. We surveyed insects collected from the South African Ni hyperaccumulator Berkheya coddii to document whole-body metal concentrations (Co, Cr, Cu, Mg, Mn, Ni, Pb, Zn). We also documented the concentrations of these metals in leaves, stems and inflorescences, finding extremely elevated levels of Ni (4 700,16 000 ,g/g) and high values (5,34 ,g/g) for Co, Cr, and Pb. Of 26 insect morphotypes collected from B. coddii, seven heteropterans, one coleopteran, and one orthopteran contained relatively high concentrations of Ni (> 500 ,g/g). The large number of high-Ni heteropterans adds to discoveries of others (from California USA and New Caledonia) and suggests that members of this insect order may be particularly Ni tolerant. Nymphs of the orthopteran (Stenoscepa) contained 3 500 ,g Ni/g, the greatest Ni concentration yet reported for an insect. We also found two beetles with elevated levels of Mg (> 2 800 ,g/g), one beetle with elevated Cu (> 70 ,g/g) and one heteropteran with an elevated level of Mn (> 200 ,g/g). Our results show that insects feeding on a Ni hyperaccumulator can mobilize Ni into food webs, although we found no evidence of Ni biomagnification in either herbivore or carnivore insect taxa. We also conclude that some insects associated with hyperaccumulators can contain Ni levels that are high enough to be toxic to vertebrates. [source] Seasonal fluctuations of selenium and sulfur accumulation in selenium hyperaccumulators and related nonaccumulatorsNEW PHYTOLOGIST, Issue 3 2007Miriam L. Galeas Summary ,,Some plants hyperaccumulate selenium (Se) up to 1% of dry weight. This study was performed to obtain insight into whole-plant Se fluxes in hyperaccumulators. ,,Selenium hyperaccumulators Astragalus bisulcatus and Stanleya pinnata were monitored over two growing seasons for seasonal fluctuations in concentrations of Se and the chemically similar element sulfur (S). The related nonhyperaccumulators Astragalus sericoleucus, Oxytropis sericea and Thlaspi montanum were included for comparison. ,,In both hyperaccumulators leaf Se decreased from April to October, coinciding with Se hyperaccumulation in flowers and seeds. Root Se levels were lowest in summer. Selenium concentration decreased with leaf age in both hyperaccumulators. Leaf S levels peaked in summer in all plant species, as did Se levels in nonhyperaccumulators. Selenium and S levels tended to be negatively correlated in hyperaccumulators, and positively correlated in nonhyperaccumulators. ,,These results suggest a specific flow of Se in hyperaccumulator plants over the growing season, from root to young leaves in spring, followed by remobilization from aging leaves to reproductive tissues in summer, and back to roots in the autumn. [source] Managing the manganese: molecular mechanisms of manganese transport and homeostasisNEW PHYTOLOGIST, Issue 3 2005Jon K. Pittman Summary Manganese (Mn) is an essential metal nutrient for plants. Recently, some of the genes responsible for transition metal transport in plants have been identified; however, only relatively recently have Mn2+ transport pathways begun to be identified at the molecular level. These include transporters responsible for Mn accumulation into the cell and release from various organelles, and for active sequestration into endomembrane compartments, particularly the vacuole and the endoplasmic reticulum. Several transporter gene families have been implicated in Mn2+ transport, including cation/H+ antiporters, natural resistance-associated macrophage protein (Nramp) transporters, zinc-regulated transporter/iron-regulated transporter (ZRT/IRT1)-related protein (ZIP) transporters, the cation diffusion facilitator (CDF) transporter family, and P-type ATPases. The identification of mutants with altered Mn phenotypes can allow the identification of novel components in Mn homeostasis. In addition, the characterization of Mn hyperaccumulator plants can increase our understanding of how plants can adapt to excess Mn, and ultimately allow the identification of genes that confer this stress tolerance. The identification of genes responsible for Mn2+ transport has substantially improved our understanding of plant Mn homeostasis. [source] Increased cysteine availability is essential for cadmium tolerance and accumulation in Arabidopsis thalianaPLANT BIOTECHNOLOGY JOURNAL, Issue 6 2004José R. Domínguez-Solís Summary Employing genetic transformation using an Atcys-3A cDNA construct expressing the cytosolic O -acetylserine(thiol)lyase (OASTL), we obtained two Arabidopsis lines with different capabilities for supplying cysteine under metal stress conditions. Lines 1-2 and 10-10, grown under standard conditions, showed similar levels of cysteine and glutathione (GSH) to those of the wild-type. However, in the presence of cadmium, line 10-10 showed significantly higher levels. The increased thiol content allowed line 10-10 to survive under severe heavy metal stress conditions (up to 400 µm of cadmium in the growth medium), and resulted in an accumulation of cadmium in the leaves to a level similar to that of metal hyperaccumulator plants. Investigation of the epidermal leaf surface clearly showed that most of the cadmium had accumulated in the trichomes. Furthermore, line 10-10 was able to accumulate more cadmium in its trichomes than the wild-type, whereas line 1-2 showed a reduced capacity for cadmium accumulation. Our results suggest that an increased rate of cysteine biosynthesis is responsible for the enhanced cadmium tolerance and accumulation in trichome leaves. Thus, molecular engineering of the cysteine biosynthesis pathway, together with modification of the number of leaf trichomes, may have considerable potential in increasing heavy metal accumulation for phytoremediation purposes. [source] | ||||||||||