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The inhibition of root growth was investigated in wheat seedlings exposed to 3 mM zinc (Zn). Zn treatment with or without 250 µM 2-phenyl-4,4,5,5,-tetrame-thylimidazoline-3-oxide-1-oxyl (PTIO) or 10 µM diphenylene iodonium (DPI) significantly inhibited growth, increased malondialdehyde content and lowered cell viability in roots. The most prominent changes of these three parameters at Zn+DPI treatment could be partly blocked by high PTIO concentration (1 mM). The production of nitric oxide (NO) and hydrogen peroxide (H2O2) influenced each other under different treatments, with the highest NO level and the highest H2O2 accumulation in Zn+DPI-treated roots. Compared with Zn-stressed roots, catalase, soluble peroxidase (POD), ascorbate peroxidase and superoxide dismutase decreased in Zn+DPI-treated roots, suggesting that ROS generation from plasma membrane (PM) NADPH oxidase was associated with the regulation of antioxidant enzyme activities. Additionally, Zn-treated roots exhibited significant decreases in cell wall-bound POD, diamine oxidase and polyamine oxidase activities. Our results suggested that Zn-induced effects on root growth resulted from NO interaction with H2O2 and that Zn+DPI-induced strongest inhibition could be explained by the highest increase in the endogenous NO content and the reduction of extracellular ROS production. [ABSTRACT FROM AUTHOR]

The growth and metal-extraction efficiency of plants exposed to toxic metals has been reported to be enhanced by inoculating plants with certain bacteria but the mechanisms behind this process remain unclear. We report results from glasshouse experiments on Brassica juncea plants exposed to 400 mg Zn kg −1 that investigated the abilities of Pseudomonas brassicacearum and Rhizobium leguminosarum to promote growth, coupled with synchrotron based μXANES analysis to probe Zn speciation in the plant roots. P. brassicacearum exhibited the poorest plant growth promoting ability, while R. leguminosarum alone and in combination with P. brassicacearum enhanced plant growth and Zn phytoextraction. Reduced growth in un-inoculated plants was attributed to accumulation of Zn oxalate and Zn sulfate in roots. In plants inoculated with P. brassicacearum the high concentration of Zn polygalacturonic acid in the root may be responsible for the stunted growth and reduced Zn phytoextraction. The improved growth and increased metal accumulation observed in plants inoculated with R. leguminosarum and in combination with P. brassicacearum was attributed to the storage of Zn in the form of Zn phytate and Zn cysteine in the root. When combined with the observation that both bacteria do not statistically improve B. juncea growth in the absence of Zn, this work suggests that bacteria-induced metal chelation is the key mechanism of plant growth promoting bacteria in toxicity attenuation and microbial-assisted phytoremediation. [ABSTRACT FROM AUTHOR]

The effects of summer green manuring crops and zinc (Zn) fertilization on quality of basmati rice during summer rainy seasons of 2008 and 2009 (kharif, April–November) were evaluated in field experiments at the research farm of the Indian Agricultural Research Institute, New Delhi. Quality parameters of basmati rice (viz., physical, biochemical, and cooking quality parameters) increased significantly as a result of summer green manure crop residue incorporation over summer fallow treatment. Incorporation of Sesbania aculeata green manure crop residues led to significantly greater protein (8.44 percent mean of 2 years) and amylose content (25.78 percent mean of 2 years). Zinc fertilization using 2 percent Zn-enriched urea (ZEU) recorded the greatest values for these parameters and also for hulling (73.8 percent mean of 2 years) and milling (62.4 percent mean of 2 years). Zinc fertilization using 2 percent ZEU and incorporation of Sesbania aculeata green manure crop residues also recorded the greatest values for all quality parameters related to cooking quality such as length and breadth of grains before and after cooking. Soil microbiological parameters and yield showed significantly high positive correlations with quality parameters. The 2-year field study clearly demonstrated the benefits of summer green manure nitrogen (N) and Zn enrichment for improving the biochemical, physical, and cooking quality parameters of basmati rice. [ABSTRACT FROM AUTHOR]

The accumulation of contaminants in the environment due to anthropogenic activities is a matter of global concern. Solanum nigrum L. plants, able to accumulate zinc and hyperaccumulate cadmium, were challenged with 0.025 g Zn L during 35 days. The localization of Zn in roots, stems and leaves of S. nigrum plants was evaluated by autometallography (AMG) in order to determine the specific tissue, cell and subcellular compartments of Zn sequestration. This Zn concentration resulted in stunted plant growth but no other symptoms of Zn toxicity. Zinc concentration in the plants was highest in the roots, 666 mg Zn kg fresh weight (f.w.), and lower in the stems, 318 mg Zn kg f.w., and leaves, 101 mg Zn kg f.w. Roots of Zn-treated plants showed an underdeveloped structure but additional layers of proliferating cortical parenchyma cells. AMG of S. nigrum roots, stems and leaves revealed a generalized Zn distribution associated with the cell walls in all tissues. In the vasculature (xylem and phloem), Zn was observed at the plasma membrane-cell wall complex of vascular parenchyma cells and conducting elements. Conspicuous Zn deposits were detected in the vacuoles of cortical parenchyma and starch sheath, as well as in the tonoplast of the mesophyll cells. Our results suggest that Zn flux through the plant occurs via the xylem and phloem and associated parenchyma until it is conducted to permanent storage sites, namely, the apoplast and vacuoles of cortical parenchyma cells of the root, stem and the leaf mesophyll. [ABSTRACT FROM AUTHOR]

The present study exemplifies morphogenic roles played by copper and zinc during micropropagation of Rauvolfia serpentina, an important medicinal shrub. Incorporation of 20 μM CuSO or 25 μM ZnSO to a Murashige and Skoog (MS) medium with optimized concentrations of auxins and cytokinins induced a maximum number of shoots per explant (40.67 ± 1.76 and 45.47 ± 0.24, respectively). However, higher concentrations of both the micronutrients negatively affected the morphogenic potential. The pigment content of the regenerants increased up to the optimal concentrations of both metals and thereafter decreased, whereas the maximum proline content was at the highest concentrations used. In vitro rooting of healthy shoots was accomplished using 0.5 μM IBA in a half strength liquid MS medium with 8.20 ± 0.37 roots, and root length of 5.50 ± 0.14 cm per microshoot. The plants survived a hardening procedure and were successfully acclimatized to field conditions with 95 % survival. [ABSTRACT FROM AUTHOR]

In the present study, the effect of excess Zn and Pb ions added to the nutrient solution of hydroponically grown sunflower plants was studied in order to evaluate their impact on the properties of leaf tissue by employing an electrolyte leakage kinetics model. Based on the behavior of model parameters, it was demonstrated that treatment with excess Zn had a stronger effect on leaf leakage kinetics than Pb. This could be attributed to the higher mobility of Zn ions which were more readily transported towards the leaves in comparison to Pb. Ion fluxes through different subcellular compartments, namely apoplast (including cell wall) and symplast (comprising the vacuole and cell membranes) were used to explain the changes in ion leakage kinetics as reflecting the functional status of cellular membranes. [ABSTRACT FROM AUTHOR]

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The purpose of the present work was to evaluate effects of zinc application on growth and uptake and distribution of mineral nutrients under salinity stress [0, 33, 66, and 99 mM sodium chloride (NaCl)] in soybean plants. Results showed that, salinity levels caused a significant decrease in shoot dry and fresh weight in non-zinc application plants. Whereas, zinc application on plants exposed to salinity stress improved the shoot dry and fresh weight. Potassium (K) concentration, K/sodium (Na) and calcium (Ca)/Na ratios significantly decreased, while sodium (Na) concentration increased in root, shoot, and seed as soil salinity increased. Phosphorus (P) concentration significantly decreased in shoot under salinity stress. Moreover, calcium (Ca) significantly decreased in root, but increased in seed with increased salinization. Iron (Fe) concentration significantly decreased in all organs of plant (root, shoot, and seed) in response to salinity levels. Zinc (Zn) concentration of plant was not significantly affected by salinity stress. Copper (Cu) concentration significantly decreased by salinity in root. Nonetheless, manganese (Mn) concentration of root, shoot, and seed was not affected by experimental treatments. Zinc application increased Ca/Na (shoot and seed) ratio and K (shoot and seed), P (shoot), Ca (root and seed), Zn (root, shoot, and seed) and Fe (root and shoot) concentration in soybean plants under salinity stress. Zinc application decreased Na concentration in shoot tissue. [ABSTRACT FROM AUTHOR]

Plant-associated bacteria can have beneficial effects on the growth and health of their host. However, the role of plant growth promoting bacteria (PGPR), under metal stress, has not been widely investigated. The present study investigated the possible mandatory role of plant growth promoting rhizobacteria in protecting plants from zinc (Zn) toxicity. The exposure of maize plants to 50 µM zinc inhibited biomass production, decreased chlorophyll, total soluble protein and strongly increased accumulation of Zn in both root and shoot. Similarly, Zn enhanced hydrogen peroxide, electrolyte leakage and lipid peroxidation as indicated by malondaldehyde accumulation. Pre-soaking with novel Zn tolerant bacterial strain Proteus mirabilis (ZK1) isolated zinc (Zn) contaminated soil, alleviated the negative effect of Zn on growth and led to a decrease in oxidative injuries caused by Zn. Furthermore, strain ZK1 significantly enhanced the activities of catalase, guaiacol peroxidase, superoxide dismutase and ascorbic acid but lowered the Proline accumulation in Zn stressed plants. The results suggested that the inoculation of Zea mays plants with P. mirabilis during an earlier growth period could be related to its plant growth promoting activities and avoidance of cumulative damage upon exposure to Zn, thus reducing the negative consequences of oxidative stress caused by heavy metal toxicity. [ABSTRACT FROM AUTHOR]

The main objectives of this study were to elucidate the roles of silicon (Si) in alleviating the effects of 2 mM zinc (high Zn) stress on photosynthesis and its related gene expression levels in leaves of rice (Oryza sativa L.) grown hydroponically with high-Zn stress. The results showed that photosynthetic parameters, including net photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO2 concentration, chlorophyll concentration and the chlorophyll fluorescence, were decreased in rice exposed to high-Zn treatment. The leaf chloroplast structure was disordered under high-Zn stress, including uneven swelling, disintegrated and missing thylakoid membranes, and decreased starch granule size and number, which, however, were all counteracted by the addition of 1.5 mM Si. Furthermore, the expression levels of Os08g02630 (PsbY), Os05g48630 (PsaH), Os07g37030 (PetC), Os03g57120 (PetH), Os09g26810 and Os04g38410 decreased in Si-deprived plants under high-Zn stress. Nevertheless, the addition of 1.5 mM Si increased the expression levels of these genes in plants under high-Zn stress at 72 h, and the expression levels were higher in Si-treated plants than in Si-deprived plants. Therefore, we conclude that Si alleviates the Zn-induced damage to photosynthesis in rice. The decline of photosynthesis in Zn-stressed rice was attributed to stomatal limitation, and Si activated and regulated some photosynthesis-related genes in response to high-Zn stress, consequently increasing photosynthesis. [ABSTRACT FROM AUTHOR]

Phytoextraction relies on plants with a high capacity to absorb heavy metals and remove them from the soil. The objective of this study was to analyze the potential of sunflower (Helianthus annuus L.) and white mustard (Sinapis alba L.) for phytoextraction of Zn-contaminated soil. Research was based on a strict pot experiment conducted in a greenhouse. Seven treatments were established with increasing Zn concentrations: 0, 25, 50, 100, 200, 400, and 600 mg Zn kg-1 air-dry soil. The first tested plant was fodder sunflower. In the following year, white mustard was sown in the same pots. Plants were harvested at the end of the flowering stage. The toxic effect of Zn on sunflower yields occurred at the contamination level of 200 mg Zn kg-1 soil. In the second year of the experiment, a significant decrease in mustard biomass took place in response to 400 mg Zn kg-1 soil. The contamination level of 600 mg Zn kg-1 soil resulted in complete plant death. Plant growth was not inhibited even at high tissue Zn concentrations of 515 mg Zn kg-1 sunflower DM and 422 mg Zn kg-1 mustard DM. The 2-yr cropping system did not contribute to a significant decrease in soil Zn content. Despite high concentrations of Zn in sunflower and mustard plants, total Zn uptake accounted for only 1% to 8% of the Zn rate introduced into the soil. However, in the long run, the growing of crops could reduce Zn contamination levels in the soil. The relatively high tolerance of sunflower and white mustard for Zn contamination and rapid growth of these species are possible alternatives for phytoextraction and phytostabilization of Zn-contaminated soil. [ABSTRACT FROM AUTHOR]

Exposing plants to non-toxic metal concentrations elicits specific detoxification mechanisms in tobacco roots that improve root membrane functionality and leaf stomatal regulation with toxic zinc in the growing medium.Evidence suggests that heavy-metal tolerance can be induced in plants following pre-treatment with non-toxic metal concentrations, but the results are still controversial. In the present study, tobacco plants were exposed to increasing Zn2+ concentrations (up to 250 and/or 500 μM ZnSO4) with or without a 1-week acclimation period with 30 μM ZnSO4. Elevated Zn2+ was highly toxic for plants, and after 3 weeks of treatments there was a marked (≥50%) decline in plant growth in non-acclimated plants. Plant acclimation, on the other hand, increased plant dry mass and leaf area up to 1.6-fold compared with non-acclimated ones. In non-acclimated plants, the addition of 250 μM ZnSO4 led to transient membrane depolarization and stomatal closure within 24h from the addition of the stress; by contrast, the acclimation process was associated with an improved stomatal regulation and a superior ability to maintain a negative root membrane potential, with values on average 37% more negative compared with non-acclimated plants. The different response at the plasma-membrane level between acclimated and non-acclimated plants was associated with an enhanced vacuolar Zn2+ sequestration and up to 2-fold higher expression of the tobacco orthologue of the Arabidopsis thaliana MTP1 gene. Thus, the acclimation process elicited specific detoxification mechanisms in roots that enhanced Zn2+ compartmentalization in vacuoles, thereby improving root membrane functionality and stomatal regulation in leaves following elevated Zn2+ stress. [ABSTRACT FROM AUTHOR]

A field experiment was conducted during the pre-kharifseason of 2012 and 2013 at Varanasi to study the effect of nitrogen, phosphorus and potassium (NPK) (100% and 125% recommended dose of fertilizer), sulfur (0, 25 and 50 kg S ha−1) and zinc (0, 5 and 10 kg Zn ha−1) fertilization on growth, yield, economics and quality of baby corn. Growth attributes like plant height, number of green leaves, stem girth, dry matter plant−1, crop growth rate (CGR), chlorophyll content of leaves, yield attributes like number of baby cobs plant−1, cob and corn weight, length and girth of corn as well as yield of cob, corn and green fodder besides gross return, net return and benefit:cost ratio were increased significantly with application of 125% RDF (recommended dose of fertilizer) over 100% RDF. Increasing level of sulfur application up to 50 kg S ha−1had a marked effect on all the growth characters, yield attributes and yield. Each increment of zinc application up to 10 kg Zn ha−1correspondingly improved growth, yield attributes, cob yield, corn yield and green fodder yield as well as gross return, net return and the benefit:cost ratio. [ABSTRACT FROM PUBLISHER]

Accumulation and distribution of Zn and Cd in the hyperaccumulator plant Sedum plumbizincicola were investigated in a hydroponic experiment. Mean Cd and Zn concentrations in shoots (7,010 and 18,400 mg kg) were about sevenfold and fivefold higher than those in roots (840 and 3,000 mg kg) after exposure to 100 μM CdSO and 600 μM ZnSO, respectively. Cd and Zn concentrations in young leaves (4,330 and 9,820 mg kg) were about sixfold and twofold higher than those in mature leaves (636 and 2,620 mg kg), respectively. MicroPIXE analysis showed that Zn was predominantly localized in epidermal cells in both young and mature leaves, but large amounts of Zn occurred in mesophyll cells in young leaves. Leaf tissue fractionation showed that soluble and cell wall fractions were different at the two stages of leaf growth. Young and mature leaves of S. plumbizincicola also showed different accumulation and distribution characteristics for Zn and Cd. [ABSTRACT FROM AUTHOR]

Abstract: Contamination of soil and water by heavy metals has become a widespread problem; environmental pollution by high zinc (Zn) concentration occurs frequently. Although poplar (Populus spp.) has been identified as suitable for phytoremediation approaches, its response to high Zn concentrations are still not clearly understood. For this reason, we investigated the effects of Zn in Populus × euramericana clone I-214 roots by proteomic analysis. Comparative experiments were conducted on rooted woody cuttings grown in nutrient solutions containing 1mM (treatment) or 1μM (control) Zn concentrations. A gel-based proteomic approach coupled with morphological and chemical analysis was used to identify differentially represented proteins in treated roots and to investigate the effect of Zn treatment on the poplar root system. Data shows that Zn was accumulated preferentially in roots, that the antioxidant system, the carbohydrate/energy and amino acid metabolisms were the main pathways modulated by Zn excess, and that mitochondria and vacuoles were the cellular organelles predominately affected by Zn stress. A coordination between cell death and proliferation/growth seems to occur under this condition to counteract the Zn-induced damage. [Copyright &y& Elsevier]

Nitrogen (N) and zinc (Zn) are the two major yield-limiting factors of flooded rice cultivation systems. Both nutrients interact and affect availability of the other in alkaline calcareous soils. In order to evaluate the interactive effects of N and Zn on yield and quality of Basmati rice, a field study was conducted at Sheikhupura (Site I) and Sargodha (Site II), Pakistan. Nitrogen treatments (0, 40, 80, 120 and 160 kg/ha) were kept in main blocks while zinc levels (0, 8, 10, 12 and 14 kg/ha) were kept in sub blocks. The main effects of N and Zn levels were significant for grain yield and yield attributes. N and Zn interaction significantly improved the grain yield, yield components and all kernel quality parameters, except kernel amylose contents. Combined application of 120 kg N/ha and 14 kg Zn/ha produced the maximum grain yields at both sites (6.12 and 5.78 t/ha). This combination also yielded the maximum kernel lengths and widths, water absorption ratio and kernel protein contents. There was a significant positive correlation between grain yield and total dry matter, panicle-bearing tillers, spikelets panicle, grain weight, and harvest index. Application of 160 kg N/ha was detrimental to yield and quality attributes and reduced the agronomic efficiency of N use at both sites. Site comparison showed that soil pH and soil nutrient contents play a significant role in determination of the optimum nitrogen and zinc fertilizer doses for maximum yields. [ABSTRACT FROM AUTHOR]

A greenhouse experiment was conducted to evaluate the effect of four different amendments, bone mill, bottom ash, furnace slag, and red mud, as immobilizing agents and the plant species Miscanthus sinensis and Pteridium aquilinum in aided phytostabilization of Pb/Zn mine tailings. The effects of amendments and plants on the availability and mobility of heavy metals were evaluated using single extraction, sequential extraction, pore-water analysis, and determination of heavy metal concentrations in plants. The application of Fe-rich amendments significantly reduced the amount of soluble and extractable heavy metals in the tailings (p < 0.05). Furnace slag and M. sinensis reduced CaCl2-extractable heavy metals by 56–91%, red mud and P. aquilinum treatment was the most effective at decreasing bioaccessible Pb, reducing it to 34% of the total Pb. Compared to control, water soluble Cd, Cu, Pb, and Zn were reduced by 99, 99, 98, and 99%, respectively, in the red mud and P. aquilinum tailings. M. sinensis accumulated heavy metals mainly in the root, and had lower translocation factors compared with P. aquilinum. The results of this study suggest that M. sinensis can be used in aided phytostabilization for these types of mine tailings and Fe-rich amendments are effective for the in situ immobilization of metals. [Copyright &y& Elsevier]

Highlights: [•] [Zn(Gly)2] was more effective than Zn-sulfate in supplying Zn for lettuce. [•] [Zn(Gly)2] was more effective in reducing Na and enhancing K and Ca in salt-exposed lettuce. [•] [Zn(Gly)2] reduced lipid peroxidation and enhanced crop tolerance to salt stress. [•] [Zn(Gly)2] is recommended as Zn source for hydroponically-grown lettuce particularly under saline condition. [Copyright &y& Elsevier]

Cadmium and zinc share many similar physiochemical properties, but their compartmentation, complexation and impact on other mineral element distribution in plant tissues may drastically differ. In this study, we address the impact of 10 μ m Cd or 50 μ m Zn treatments on ion distribution in leaves of a metallicolous population of the non-hyperaccumulating species Zygophyllum fabago at tissue and cell level, and the consequences on the plant response through a combined physiological, proteomic and metabolite approach. Micro-proton-induced X-ray emission and laser ablation inductively coupled mass spectrometry analyses indicated hot spots of Cd concentrations in the vicinity of vascular bundles in response to Cd treatment, essentially bound to S-containing compounds as revealed by extended X-ray absorption fine structure and non-protein thiol compounds analyses. A preferential accumulation of Zn occurred in vascular bundle and spongy mesophyll in response to Zn treatment, and was mainly bound to O/ N-ligands. Leaf proteomics and physiological status evidenced a protection of photosynthetically active tissues and the maintenance of cell turgor through specific distribution and complexation of toxic ions, reallocation of some essential elements, synthesis of proteins involved in photosynthetic apparatus or C-metabolism, and metabolite synthesis with some specificities regarding the considered heavy metal treatment. [ABSTRACT FROM AUTHOR]

The effect of nitrogen (N), phosphorous (P), sulfur (S) and zinc (Zn) fertilization on arbuscular mycorrhizal colonization (AMC), nutrition and growth of maize under contrasting tillage management was assessed in a field trial. The effect of Zn fertilization (+Zn: 1.67 mg Zn kg-1, -Zn: 0.33 mg Zn kg-1), and inoculation with four consortium with arbuscular mycorrhizal fungi (AMF) indigenous of two sites of Buenos Aires, Argentina under contrasting managements(Agricultural and Pristine), on arbuscular mycorrhizal colonization (AMC), nutrition and growth of maize was assessed in a greenhouse trial. Zinc fertilization did not affect growth or AMC under field conditions, but in greenhouse, highest dose of Zn depressed AMC. Zinnc application in greenhouse at a reduced dose resulted in symptoms of deficiency which were translated in reduced plant growth but highest mycorrhizal response (MR). The inoculum from Balcarce Agricultural (indigenous from a site with about 19 mg P kg-1 and 0.5 mg Zn kg-1) resulted in the highest AMC and MR in both Zn uptake and dry matter production. The inoculum from Coronel Dorrego Pristine (indigenous from a site with about 8 mg P kg-1 and 2.2 mg Zn kg-1) was the lowest efficient. We hypothesized that certain soil characteristics could be used to select potentially beneficial inocula to compensate Zn deficiencies in maize. [ABSTRACT FROM AUTHOR]

Zinc toxicity in secretory cells caused a range of effects, mainly depending on metal concentration. Low concentrations activated nectary function increasing nectar secretion but secretion was greatly inhibited or stopped entirely by ongoing concentration. Water loss rate of zinc treated flower parts was significantly reduced whereas green sepals were dehydrated more rapidly in comparison to colored petals. The content of zinc, calcium, magnesium and manganese increased mainly in sepals under excess of zinc, but in the secreted nectar this metal was not evident. Morphological changes were observed in mucilage cells concerning the mucilage structure and appearance. The parenchymatic, subglandular cells displayed an early vacuolarization and cytoplasm condensation. Secretory hairs appeared to be thinner, the apical cell folded inwards and plasmolytic shrinkage became severe in all cells. The waxy cuticula showed an increased electron density. A plasmalemma detachment from the external cell walls was observed creating a gap between cell wall and plasmalemma. ER cisterns of all treated nectary hairs dominated the cytoplasm and electron dense deposits were seen within its profiles. A great number of other organelles were also present, showing electron dense deposits in their membranes as well. The vacuome was drastically reduced in all cells, except in the subglandular ones and electron dense membrane remnants were observed. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the changes in leaflet zinc (Zn), leaf nutritional state, vegetative and physiological parameters, and yield quality in pecan trees sprayed with different Zn compounds. Eight-year-old 'Western Schley' pecan trees grafted to native seedlings were treated with ZnNO3 (100 mg⋅-L-1 Zn), Zn-EDTA (50, 100, and 150 mg⋅L-1 Zn), and Zn-DTPA (100 mg⋅L-1 Zn) and compared with the Zn-untreated control. After 3 years of evaluation, the trees with the best appearance were those treated with ZnNO3 (100 mg⋅L-1 Zn) and Zn-DTPA (100 mg⋅L-1 Zn), which showed leaf Zn concentration increases of 73% and 69%, respectively, when compared with the controls. The chlorophyll values of the Zn-treated trees reached 46 SPAD units, equivalent to 43 mg⋅kg-1 dry weight (DW) of chlorophyll compared with values of 22 mg⋅kg-1 DW in Zn-deficient leaves. On a leaf area basis, chlorophyll value was 37% lower under Zn deficiency conditions than that of Zn-treated trees. Nut quality was unaffected by the Zn treatments. Data suggest that Zn-DTPA and Zn-NO3 are good options to carry out foliar Zn fertilization in pecan trees. [ABSTRACT FROM AUTHOR]

Highlights: [•] Effects of nitrogen (N) management on root morphology and zinc (Zn) translocation in winter wheat were studied. [•] Increasing N supply improved root length density, surface area and root dry weight, resulting in an increased root Zn uptake. [•] Improved ratios of shoot to root Zn concentration and shoot to total Zn content indicate higher N supply promotes root to shoot Zn translocation. [•] Combination of optimum N management and a better root system could be a promising approach to improve grain Zn accumulation for human nutrition. [ABSTRACT FROM AUTHOR]

Highlights: [•] Zn tolerance and accumulation capacity of Juncus acutus were analyzed. [•] Juncus acutus survived and did not show visible Zn toxicity symptoms at 100mmoll−1 Zn. [•] The integrity and functionality of its photosynthetic apparatus were unaffected. [•] Also Zn excess did not affect water relations and absorption of mineral elements. [•] These findings suggest that Juncus acutus is a Zn-hypertolerant plant. [ABSTRACT FROM AUTHOR]

Phosphate overaccumulates in shoots in response to Zn deprivation. Results shown in this article suggest key roles of PHR1 and PHO1 and a counteractive function of PHO1;H3 in controlling root-to-shoot phosphate translocation in Arabidopsis.Interactions between zinc (Zn) and phosphate (Pi) nutrition in plants have long been recognized, but little information is available on their molecular bases and biological significance. This work aimed at examining the effects of Zn deficiency on Pi accumulation in Arabidopsis thaliana and uncovering genes involved in the Zn–Pi synergy. Wild-type plants as well as mutants affected in Pi signalling and transport genes, namely the transcription factor PHR1, the E2-conjugase PHO2, and the Pi exporter PHO1, were examined. Zn deficiency caused an increase in shoot Pi content in the wild type as well as in the pho2 mutant, but not in the phr1 or pho1 mutants. This indicated that PHR1 and PHO1 participate in the coregulation of Zn and Pi homeostasis. Zn deprivation had a very limited effect on transcript levels of Pi-starvation-responsive genes such as AT4, IPS1, and microRNA399, or on of members of the high-affinity Pi transporter family PHT1. Interestingly, one of the PHO1 homologues, PHO1;H3, was upregulated in response to Zn deficiency. The expression pattern of PHO1 and PHO1;H3 were similar, both being expressed in cells of the root vascular cylinder and both localized to the Golgi when expressed transiently in tobacco cells. When grown in Zn-free medium, pho1;h3 mutant plants displayed higher Pi contents in the shoots than wild-type plants. This was, however, not observed in a pho1 pho1;h3 double mutant, suggesting that PHO1;H3 restricts root-to-shoot Pi transfer requiring PHO1 function for Pi homeostasis in response to Zn deficiency. [ABSTRACT FROM AUTHOR]

The bacteria of PDMCd0501, PDMCd2007, and PDMZnCd2003 were isolated from a Zn/Cd contaminated soil. They were classified as salt-tolerant bacteria in this experiment. The bacteria had indole-3-acetic acids (IAA) production, nitrogen fixation, and phosphate solubilization, under 8% (w/v) NaCl condition. Biochemical test (API 20E) and 16S rDNA sequencing identified PDMCd2007 and PDMCd0501 as Serratia sp. and PDMZnCd2003 was Pseudomonas sp. The effect of Pseudomonas sp. PDMZnCd2003 on the germination and seedlings of Oryza sativa L.cv. RD6 was determined under a salinity of 0-16 dS/m. The salinity levels of 4-16 dS/m affected to decrease germination and seedlings of rice. Comparison between uninoculated and inoculated system, however, Pseudomonas sp. PDMZnCd2003 had a negative impact on the rice growth. This unexpected effect was a case that should be concerned and studied further before application as a plant growth-promoting bacteria (PGPB). [ABSTRACT FROM AUTHOR]

Gardens near the lead and zinc smelter plant "Zletovo" in the town of Veles, Republic of Macedonia, are the main suppliers with vegetables and fruits for the residents of this town. This area, was exposed thirty years to high environmental contamination with heavy metals (Cd, Pb and Zn). The smelter plant was a major source of heavy met-als pollution in the environment, including the garden soils used for the production of vegetables and fruits. The aim of this study is to determine the level of contamination (especially with Cd, Pb and Zn) in green garlic (Allium sa-tivum) and green onion (Allium scallion) produced on the contaminated soil and to determine its level of accumula-tion in the plants. The contents of 21 elements (Ag, Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, Pb, Sr, V and Zn) in the vegetables and corresponding soils were analyzed by inductively coupled plasma - atomic emis-sion spectrometry (ICP-AES) after microwave digestion. It was found that the contents of Cd, Pb and Zn in the vege-tables from all of the four studied gardens is over the maximum permissible level according to the Macedonian regu-lations. The content of Cd in washed green garlic samples ranges from 0.60 to 2.70 mg kg-1, for Pb from 4.30 to 6.14 mg kg-1 and for Zn from 11.7 to 29.9 mg kg-1, while their contents in the washed green onion samples ranges from 0.77 to 2.66 mg kg-1 for Cd, from 3.98 to 5.35 mg kg-1 for Pb and from 21.2 to 38.0 mg kg-1 for Zn. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess physiological quality of seeds and the initial growth of lowland rice seedlings, cv. PUITA INTA-CL, treated with a product based on Zinc, Boron and Molybdenum. The following dosages of product were used: 0 (control), 50, 100, 150 and 200 mL.100 kg-1seed. A completely randomized experimental design was used, with 10 treatments and four replications. Physiological quality of seeds was assessed by following tests: germination; first count of germination; and length and dry phytomass of seedlings. The initial growth was assessed at 7, 14, 21, 35, and 42 days after emergence (DAE) through plant height, leaf area and dry phytomass of aerial parts and roots. It was concluded that the treatment of rice seeds with the product containing Zinc, Boron and Molybdenum up to the dosage tested of 200 mL.100 kg-1 seed does not influence germination, first count of germination, and the dry phytomass of aerial parts and roots; however, negatively influences seedling length. In addition, it also promotes greater plant height, higher leaf area, higher production of dry phytomass of seedlings, and increase on the growth rate, until 42 DAE. [ABSTRACT FROM AUTHOR]

An experiment was conducted at the Agricultural Research Institute, Dera Ismail Khan, in 2009, to determine the effect of micronutrients viz. zinc, boron and iron on growth and yield of rice. The experiment was laid out in a randomized complete block design with four replications. The results revealed that the maximum number of tillers per square meter, spikelets per panicle and paddy yield was obtained with combined use of zinc and boron. Whereas, the highest 1000-grain weight was recorded where all three micronutrients (zinc, boron and iron) were applied in combination. The maximum normal kernel percentage was recorded where zinc was applied along with iron while the maximum number of panicles per square meter was recorded with sole iron application. Based on results obtained, it is recommended to use boron alone or combined it with zinc for obtaining higher yield of rice. [ABSTRACT FROM AUTHOR]

Sedum alfrediiHance is a fast-growing and high-biomass zinc (Zn) hyperaccumulator native to China. A compound containing substituted indole ligand was isolated from this Zn hyperaccumulator plants by sonication/ethanol extraction, macroporous resin column as well as preparative HPLC (P-HPLC). Hydroponic experiment showed that the concentrations of both Zn and the compound containing substituted indole ligand were remarkably increased in stems and leaves of both hyperaccumulator and non-hyperaccumulator as Zn rising from 0.5 to 50 μmol L−1, with much more in the stems of hyperaccumulator than non-hyperaccumulator. At 50 μmol L−1Zn, hyperaccumulator grew normally but its non-hyperaccumulator suffered from strongly Zn-induced toxicity. This suggested that there was a positive correlation between the compound containing substituted indole ligand and Zn concentration in shoots of hyperaccumulatorS. alfredii. [ABSTRACT FROM PUBLISHER]

The effect of pyrolysis temperature on the characteristics and metal sorption capacity of sugar cane straw derived--biochar (BC) was investigated. Biochar was produced at four temperatures (400, 500, 600, and 700 °C) before characterization for yield, ash and moisture content, pH, EC, pHPZC, elemental composition, nutrient content, CEC, TGA, and functional groups (FT-IR). Biochar alone and in mixtures containing 10%, w/w biochar with one of two different tropical soils (Entisol and Oxisol) was shaken for 24 h with a 2.0 mM solution (pH 4.5) of Zn or Cd in a batch sorption test. Increasing the pyrolysis temperature led to a reduction in the O/C and H/C molar ratios. The sorption capacity of biochar pyrolyzed at 700 °C was nearly four times greater than that produced at 400 °C. In the Entisol mixture, there was an increase up to seven-fold in the sorption of both Cd and Zn compared with the control (without BC). In the Oxisol mixture, there was a maximum 20% increase in sorption compared with the control. For the remediation of Cd- and Zn-contaminated substrates, the use of higher pyrolysis temperature biochars are recommended because of their higher metal sorption capacities. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine and compare levels of heavy metals in the leaves of Plantago major and the soil near the root zone. The study was conducted in the region of Durrës city, in Albania. The metals studied in this work were Pb, Cu, Zn, Mn, and Ni. Heavy metals presented in leaves of plants and soil have been detected using an atomic absorber spectrophotometer model NovAA400 (Analitik Jena). The results show that the determined metals were present in the soil and leaves of Plantago major. The concentrations of metals found in soil change in the order Zn>Pb>Ni>Mn>Cu. The highest concentration was found for Zn and Pb. In our study, results showed a good correlation between Pb and Zn in the soil, suggesting the same origin of pollution. Plantago major showed the ability to absorb metals and the concentration of metals in leaves showed a good correlation with the concentration of metals in soil. [ABSTRACT FROM AUTHOR]

The purpose of our work was to evaluate the seed germination ability of native species representing calamine populations of Alyssum montanum, Biscutella laevigata (Brassicaceae), and Dianthus carthusianorum (Caryophyllaceae). As substrata for germination, calamine substrate on which populations of examined plant species were grown in natural conditions, and horticultural substrate constituting a mixture of sand and garden soil were used. A. montanum and B. laevigata seeds demonstrated a high ability to germinate on calamine substrate, which was characterized by large contents of soluble forms of zinc (115.1 mg•kg-1), lead (0.91 mg•kg-1), and cadmium (3.12 mg•kg-1), and low water capacity (18.95% g/g). The seed germination ability of calamine Dianthus carthusianorum ecotype was comparable on both studied substrata types. [ABSTRACT FROM AUTHOR]

This study was conducted for evaluating the combined effect of soil moisture, phosphorus (P) and zinc (Zn) levels on crop evapotranspiration (ET), leaf water potential (LWP), water use efficiency (WUE) and various tuber attributes of potato (Solanum tuberosum L. cv. Agria) under greenhouse conditions. This investigation was conducted as a factorial experiment based on randomized complete blocks design with Zn at three levels (0, 10 and 20mg Zn per kg dry soil as ZnSO4·7H2O), P at three levels (0, 30 and 60mg P per kg dry soil as Ca(H2PO4)2·H2O) and soil moisture at three levels (0.5 FC–0.6 FC, 0.7 FC–0.8 FC and 0.9 FC–FC) using three replications. The various attributes of potato tubers including tuber numbers, dry matter content (DM), yield, WUE and indicators of water deficit stress intensity (ET and LWP) were measured routinely during the crop growth period. The results showed that the water deficit stress resulted in a significant decrease in ET, tuber numbers, yield and WUE. Application of P significantly increased the ET, tuber numbers and yield and Zn application significantly affected the tuber numbers. The P×soil moisture interaction effect was significant for ET, LWP, tuber numbers and yield. While the Zn×soil moisture interaction was significant only for yield. The results showed that the two way interactions of Zn, P and soil moisture were mainly synergistic on the most of above mentioned attributes. In general, to achieve the optimum yield of potato tubers in similar soils, application of 10mg Zn and 30mg P per kg of dry soil could be recommended under full-irrigated conditions. The regression analysis showed that the yield of potato was increased by application of P under water deficit conditions. [ABSTRACT FROM AUTHOR]

Zinc is the most widespread deficient micronutrient in the tea growing soils of India which affects growth of the plants. In order to investigate the structural, physiological, and biochemical changes under Zn stress ( i.e. both deficient and excess supply) of tea [ Camellia sinensis (L.) O. Kuntze cv. T-78] plants, we treated young plants with ZnSO at 0 (deficiency), 0.3, 3 (optimum), and 30 μM (toxic) concentrations for 8 weeks. Zn deficiency and excess resulted in considerable decrease in shoot and root fresh and dry masses, and transmission electron microscopy (TEM) revealed disorganization of some cellular organelles. Further, Zn-stress decreased net photosynthetic rate (P), transpiration rate (E), stomatal conductance (g), and content of chlorophylls a and b. On the other hand, content of superoxide anion, malondialdehyde, hydrogen peroxide, and phenols, and electrolyte leakage were elevated in stressed plants. The activities of ascorbate peroxidase, catalase, superoxide dismutase, and peroxidase as well as expression of respective genes were up-regulated under Zn-stress. Nevertheless, antioxidant system as a whole did not afford sufficient protection against oxidative damage. [ABSTRACT FROM AUTHOR]

Aims: Phytosiderophore-chelated Zn can be absorbed in grasses. Root exudates of dicotyledonous plants can mobilize soil Zn but it is unclear how this affects Zn bioavailability. Stable Zn isotope shifts can indicate exudate-facilitated Zn uptake, since complexation of Zn by organic ligands in solution yields a small, but detectable, enrichment of the heavy Zn isotope due to thermodynamic fractionation. Methods: Tomato seedlings were grown in resin-buffered nutrient solution in which free Zn concentrations are buffered, in a factorial design of two Zn levels and two solution volumes. The latter factor allowed altering the exudate concentrations in the solution. Dissolved Cu concentrations in the resin buffered system were used as a sensitive index of metal mobilization resulting from root activity. In addition, seedlings were grown in Zn deficient soil with and without Zn addition. Results: The dissolved Cu concentration increased with Zn deficiency and was highest at the lowest solution volume, suggesting metal mobilization by root exudates. At low Zn supply, Zn in the plant was enriched in heavy Zn (Zn) and this was most pronounced at small solution volume. Similarly, Zn deficiency in soil enriched tomato shoot Zn with heavy isotope in this plant. Interpretation: Zinc deficiency increases the contribution of Zn-exudate complexes, which are enriched in the heavy isotope compared to the free ion, to Zn uptake by transporting Zn from the bulk solution or soil to the roots where they likely dissociate and release Zn. [ABSTRACT FROM AUTHOR]

Interactive effects of zinc (Zn) × nitrogen (N) was investigated in field experiment on wheat (Triticum aestivumL., cv. ‘Saleem-2000’) at the Research Farm of KPK Agricultural University Peshawar during winter 2006–2007. The experiment consisted of four levels of N (0, 50, 100 and 100 kg N ha−1) as main plots, and six levels of Zn (0, 3, 6, 9, 12 and 15 kg Zn ha−1) as sub plots. Application of 150 kg N and 15 kg Zn ha−1resulted in the improved growth, highest yield components as well as the highest grain yield (4044 kg ha−1) and straw yield (5067 kg ha−1) of wheat. It is concluded from the results that combine application of 150 kg N +15 kg Zn ha−1could increase wheat productivity in the study area. [ABSTRACT FROM PUBLISHER]

Abstract: Nitrogen form has been shown to affect Zn uptake, translocation and storage in the Zn-hyperaccumulating plant Noccaea caerulescens but the biochemical processes are not fully understood. Organic acids and amino acids have been implicated in Zn transport and storage. This study aimed to examine the effect of N form on concentrations of organic acids and amino acids and how these metabolites correlated with Zn hyperaccumulation. Plants were grown in nutrient solution with NO3 −, NH4NO3 or NH4 +, supplied with 50 or 300μM Zn, and buffered at either pH 4.5 or 6.5. The metabolomic profile was determined by gas chromatography mass spectroscopy. The concentration of Zn in shoots, xylem and roots was greatest for the NO3 −, pH 6.5 and 300μM Zn treatments. For all N forms, the lower growth-medium pH raised xylem sap pH but had no influence on Zn concentration or exudation rate of the xylem sap. Nitrate enhanced organic acid production while NH4 + increased amino acid production. Organic acids in the xylem were more responsive to changes in growth-medium pH than N form, and did not correlate with Zn concentration in shoots, roots or xylem. Serine might be directly involved in Zn hyperaccumulation. Phosphoric acid was associated with reduced Zn accumulation in the shoots. Malic acid was not detected in the shoots but responded to cation uptake more than to Zn specifically in the roots. Citric acid responded to cation uptake more than to Zn specifically in the shoots but did not correlate with Zn concentration in the roots or the xylem sap, or any other cations in the roots. In conclusion, organic acids in N. caerulescens are not specifically involved in Zn hyperaccumulation but are involved in regulating pH in the xylem and cation–anion balance in plants. [Copyright &y& Elsevier]

Abstract: Phytoremediation is a plant based, cost effective technology to detoxify or stabilise contaminated soils. Fast growing, high biomass, perennial plants may be used not only in phytoremediation but also in energy production. Szarvasi-1 energy grass (Elymus elongatus subsp. ponticus cv. Szarvasi-1), a good candidate for this combined application, was grown in nutrient solution in order to assess its Cd, Cu, Ni, Pb and Zn accumulation and tolerance. Its shoot metal accumulation showed the order Pb < Ni < Cu ∼ Cd < Zn. In parallel with this, Pb and Ni had no or very little influence on the growth, dry matter content, chlorophyll concentration and transpiration of the plants. Cu and Cd treatment resulted in significant decreases in all these parameters that can be attributed to Fe plaque formation in the roots suggested by markedly increased Fe and Cu accumulation. This came together with decreased shoot and root Mn concentrations in both treatments while shoot Cu and Zn concentrations decreased under Cd and Cu exposure, respectively. Zn treatment had no effect or even slightly stimulated the plants. This may be due to a slight stimulation of Fe translocation and a very efficient detoxification mechanism. Based on the average 300 mg kg−1 (dry mass) Zn concentration which is 0.03% of the shoot dry mass the variety is suggested to be classified as Zn accumulator. [Copyright &y& Elsevier]

Improving P use efficiency (PUE) is desirable but difficult due to poor phosphorus (P) solubility in soils. A dicarboxylic acid copolymer (AVAIL®) fertilizer additive may enhance PUE. Monoammonium phosphate (MAP) at 67 kg P2O5ha−1was applied with or without AVAIL addition compared to an untreated check applied to potato on five field sites. MAP + AVAIL resulted in significant US No. 1 and total yield increases at two and three sites, respectively. Generally, the other sites showed similar trends. However, MAP + AVAIL resulted in a significant decrease in yields at one site possibly due to a P-induced micronutrient deficiency. Petiole P concentration of MAP + AVAIL-treated plants was significantly greater than the other treatments at mid and late season sampling dates at all sites. Addition of AVAIL with MAP applied to potato was generally effective, but concurrent fertilization with micronutrients is likely warranted due to possible antagonism with P. [ABSTRACT FROM PUBLISHER]

A variety of zinc (Zn) fertilizer sources are applied with varied responses on calcareous soils in Thailand. Seed treatment is an alternative method to deliver Zn to corn and alleviate Zn deficiency. To address this Zn delivery methods we conducted greenhouse studies on corn grown in three calcareous soils of Thailand to three Zn fertilizer sources [zinc sulfate (ZnSO4), Zn-ethylenediaminetetraacetic acid (EDTA) and Zn citrate]. We also evaluated effectiveness of soaking corn seed in three concentrations of ZnSO4(0.4, 0.8 and 1.6%) prior to planting compared to soil applied methods. Applications of zinc increased the growth, dry matter yield and zinc uptake of corn with few differences observed among the types of fertilizers. Seed soaking with ZnSO4solution also increased Zn uptake, growth rate and yield comparable to soil-applied Zn. Seed soaking prior to planting is an effective and efficient method to supply Zn to corn grown in Zn deficient calcareous soils of Thailand. [ABSTRACT FROM PUBLISHER]

AtHMA4 was previously shown to contribute to the control of Zn root-to-shoot translocation and tolerance to high Zn. However, heterologous expression of 35S:: AtHMA4 in tobacco ( N icotiana tabacum cv. Xanthi) results in enhanced Zn sensitivity. This study provides a better understanding of the development of this Zn-sensitive phenotype and demonstrates that substantial modifications of Zn homeostasis occur due to AtHMA4 expression. We show that ectopically expressing AtHMA4 in tobacco results in overloading the root and leaf apoplast with Zn. The tissue and cellular distribution of Zn, monitored using Zinpyr-1, was altered in the AtHMA4-expressing plants compared with wild type. Increased loading of the leaf apoplast with Zn in AtHMA4 transformants induced necrosis; this appeared at lower levels of Zn supply in the transgenics compared with wild type. This study suggests that Zn concentration may be sensed in the apoplast of leaves, and if concentrations are above a certain threshold then particular groups of cells accumulate Zn and necrosis is initiated. Therefore, this could be considered as a mechanism for protecting the other parts of the photosynthetically active leaf from Zn toxicity. [ABSTRACT FROM AUTHOR]

Amino acids (AA) as metal complexing agents have the ability to form relatively stable complexes with zinc (Zn) and thereby increase its availability for plants. In this study, the complexes of Zn(II), [Zn(L-L′)] [where L-L′ = monoanion of arginine (Arg), glycine (Gly), glutamine (Gln), histidine (His), and methionine (Met)], were synthesized and characterized by different analytical techniques. The results of elemental analysis support the formation of Zn(II)-AA complexes (ZnAAC) with a 2:1 ligand-to-metal molar ratio. The computational results indicated that the AA ligands coordinated to the Zn(II) ion via their nitrogen and oxygen atoms and support the coordination mode obtained from IR spectroscopy. For the first time, the semiempirical calculations were also performed to investigate the passive uptake of ZnAAC by root cells. The proposed transport pathway indicated that ZnAAC can pass via plant root cell wall pores without any strict hindrances. The efficacy of ZnAAC as a Zn source was evaluated for two lettuce cultivars ( Lactuca sativa L., cvs. 'Lollo Bionda' and 'Lollo Rossa') grown in nutrient solution. The results confirmed the higher efficacy of ZnAAC in supplying Zn for lettuce in comparison with ZnSO. The synthesized ZnAAC also had a stimulating effect on root and shoot growth of both lettuce cultivars. According to the results, ZnAAC can be used as ecofriendly plant growth stimulators and sources of Zn to supply plants with readily available Zn. [ABSTRACT FROM AUTHOR]

Zinc (Zn) is an essential micronutrient which affects plant growth and development in deficiency and can be toxic when present in excess. In Arabidopsis thaliana, different families of cation transporters play pivotal roles in Zn homeostasis. In the present study, we evaluated the effects of Zn in its deficiency (0 µM; Zn-) and excess (75 µM; Zn++) on various morphophysiological and molecular traits. Primary root length was reduced in Zn– seedlings, whereas there were significant increases in the number and length of lateral roots under Zn– and Zn++ conditions, respectively. Concentration of various macro- and microelements showed variations under different Zn regimes and notable among them was the reduced level of iron (Fe) in Zn++ seedlings compared to Zn+. Certain members of the ZIP family (ZIP4, ZIP9, and ZIP12) showed significant induction in roots and shoots of the Zn– seedlings. Their suppression under Zn++ condition indicated their transcriptional regulation by Zn and their roles in the maintenance of its homeostasis. Zn-deficiency-mediated induction of HMA2 in roots and shoots suggested its role in effluxing Zn into xylem for long-distance transport. Attenuation in the expression of Fe-responsive FRO2 and IRT1 in Zn– roots and their induction in Zn++ roots provided empirical evidence toward the prevalence of a cross talk between Zn and Fe homeostasis. Variable effects of Zn– and Zn++ on the expression of subset of genes involved in the homeostasis of phosphate (Pi), potassium (K), and sulfur (S) further highlighted the prevalence of cross talk between the sensing and signaling cascades of Zn and macronutrients. Further, the inducibility of ZIP4 and ZIP12 in response to cadmium (cd) treatment could be harnessed by tailoring them in homologous or heterologous plant system for removing pollutant toxic heavy metals from the environment. [ABSTRACT FROM AUTHOR]

Sedum alfredii is one of a few species known to hyperaccumulate zinc ( Zn) and cadmium ( Cd). Xylem transport and phloem remobilization of Zn in hyperaccumulating ( HP) and nonhyperaccumulating ( NHP) populations of S. alfredii were compared., Micro- X-ray fluorescence (μ- XRF) images of Zn in the roots of the two S. alfredii populations suggested an efficient xylem loading of Zn in HP S. alfredii, confirmed by the seven-fold higher Zn concentrations detected in the xylem sap collected from HP, when compared with NHP, populations. Zn was predominantly transported as aqueous Zn (> 55.9%), with the remaining proportion (36.7-42.3%) associated with the predominant organic acid, citric acid, in the xylem sap of HP S. alfredii., The stable isotope 68 Zn was used to trace Zn remobilization from mature leaves to new growing leaves for both populations. Remobilization of 68 Zn was seven-fold higher in HP than in NHP S. alfredii. Subsequent analysis by μ- XRF, combined with LA- ICPMS (laser ablation-inductively coupled plasma mass spectrometry), confirmed the enhanced ability of HP S. alfredii to remobilize Zn and to preferentially distribute the metal to mesophyll cells surrounding phloem in the new leaves., The results suggest that Zn hyperaccumulation by HP S. alfredii is largely associated with enhanced xylem transport and phloem remobilization of the metal. To our knowledge, this report is the first to reveal enhanced remobilization of metal by phloem transport in hyperaccumulators. [ABSTRACT FROM AUTHOR]

Zinc (Zn) is an essential micronutrient for plants, playing catalytic or structural roles in enzymes, transcription factors, ribosomes and membranes. In humans, Zn deficiency is the second most common mineral nutritional disorder, affecting around 30% of the world's population. People living in poverty usually have their diets based on milled cereals, which contain low Zn concentrations. Biofortification of crops is an attractive cost-effective solution for low mineral dietary intake. In order to increase the amounts of bioavailable Zn in crop edible portions, it is necessary to understand how plants take up, distribute and store Zn within their tissues, as well as to characterize potential candidate genes for biotechnological manipulation. The Metal Tolerance Proteins (MTP) were described as metal efflux transporters from the cytoplasm, transporting mainly Zn2+ but also Mn2+, Fe2+, Cd2+, Co2+ and Ni2+. Substrate specificity appears to be conserved in phylogenetically related proteins. MTPs characterized so far in plants have a role in general Zn homeostasis and tolerance to Zn excess; in tolerance to excess Mn and also in the response to Fe deficiency. More recently, the first MTPs in crop species have been functionally characterized. In Zn hyperaccumulator plants, the MTP1 protein is related to hypertolerance to elevated Zn concentrations. . Here, we review the current knowledge on this protein family, as well as biochemical functions and physiological roles of MTP transporters in Zn hyperaccumulators and non-accumulators. The potential applications of MTP transporters in biofortification efforts are discussed. [ABSTRACT FROM AUTHOR]

The usually negative, but variable electrical potential (ψ0) at the cell membrane (CM) surface influences the surface activities of free ions and the electrical driving force for the transport of ions across the CM. The rhizotoxic effects and uptake of Zn2+ and CO2+ singly and in binary mixture in wheat (Triticum aestivum L.) at three pH values (4.5, 5.5, or 6.1) were examined in terms of the free ion activities of Zn2+, CO2+, and H+ at the CM surface (these ions are denoted {Mn+}0). Toxicity and uptake of Zn2+ or CO2+ singly to roots were better correlated with {M2+}0 than with their bulk-phase activities. Studies of toxicant interactions using the electrostatic approach and a response-multiplication model for toxicant mixtures indicated that {CO2+}0 significantly enhanced the toxicity of {Zn2+}0, but {Zn2+}0 did not significantly affect the toxicity of {CO2+}0. {H+}0 substantially enhanced the toxicity of both metal ions. Taking ψo into account improved the correspondence (denoted r²) between observed and predicted uptake of both Zn2+ and CO2+, and each inhibited the uptake of the other. Results showed that r² increased from 0.776 to 0.936 for Zn uptake and improved from 0.805 to 0.951 for Co uptake. Thus electrostatic models for metal toxicity and uptake proved superior to models incorporating only bulk-phase activities of ions. [ABSTRACT FROM AUTHOR]

The objective of the present experiment was to estimate the uptake of manganese (Mn) and zinc (Zn) by cucumber in closed hydroponic systems at different Mn and Zn concentrations in the recycled nutrient solution under Mediterranean climatic conditions. The obtained data might be used to manage Mn and Zn supply in closed hydroponic crops of cucumber grown in Mediterranean greenhouses and avoid their accumulation to toxic levels. Four Mn levels (10, 40, 80, 120 µM) at a standard Zn concentration (6 µM) and four Zn levels (6, 20, 40, 60 µM) at a standard Mn concentration (10 µM) in the solution supplied to compensate for nutrient and water uptake by plants were applied as experimental treatments. The actual uptake concentrations of Mn and Zn were estimated by applying two different methods. The first method was based on the removal of Mn, Zn, and water from the recycling nutrient solution, whereas the second method was based on the total quantities of Mn and Zn that were recovered in plant biomass in combination with the total water uptake. Both methods gave similar uptake concentrations for Mn in the low-Mn supply level and Zn in all Zn levels. However, in the three higher Mn supply levels, the values estimated on the basis of nutrient removal from the recirculating nutrient solution were significantly higher than those found by measuring the total Mn content in plant biomass. These discrepancies in the three high-Mn treatments were possibly caused by partial immobilization of Mn by oxidizing bacteria in the nutrient solution. [ABSTRACT FROM AUTHOR]

The article focuses on the effects of ferric and zinc ions on the structural and thermodynamic properties of a soybean abscisic acid-, stress-, and ripening-induced (ASR) protein. It states that soybean ASR proteins have three ferric ion and two zinc ion binding sites and the binding sites remain disorder in the presence of ferric ions. It informs that soybean ASR protein exhibits ferric ion-binding-dependent anti-oxidant activity in vitro that protects against the oxidation damage.

Pearl millet [Pennisetum glaucum (L.) R. Br.] is an important staple food crop in the semiarid tropical regions of Asia and Africa. As part of a major initiative to improve its grain Fe and Zn densities, two sets of line × tester studies were conducted. Results showed that the underlying physiological processes determining the grain Fe and Zn densities were largely under additive genetic control, and Fe and Zn densities of the inbred lines per se and their general combining ability (GCA) were positively and highly significantly correlated. This would imply that recurrent selection can be effectively used to improve the breeding populations for grain Fe and Zn densities and that breeding lines selected for high Fe and Zn densities per se are more likely to include those with high GCA for these micronutrients. Lack of better-parent heterosis indicated that to breed hybrids with high Fe and Zn densities would require high levels of these micronutrients in both parental lines. Highly significant and positive correlations between the Fe and Zn densities, between the GCA of Fe and Zn densities, and between the specific combining ability (SCA) of the Fe and Zn densities showed that simultaneous selection for both micronutrients is likely to be effective with respect to all these performance parameters. Consistency in the patterns of results across both sets of trials and across the environments for all the parameters implies that these results could be of wider application to the genetic improvement of Fe and Zn densities in pearl millet. [ABSTRACT FROM AUTHOR]