Shoot Mn Concentrations Research Articles

Dynamics of Fe, Mn, and potentially harmful elements under reducing conditions in iron ore tailings after dam collapse in the Doce River basin-Brazil: flooded and non-flooded rice cultivations.

Potentially harmful element (PHE) bioavailability is important to environmental contamination and must be checked under several soil conditions. This study aimed to assess Fe, Mn, and PHE uptake by rice (Oryza sativa) grown on flooded and non-flooded Fe tailings collected from the Doce River basin after its collapse in Brazil. After 65days of sowing, shoots and roots were harvested to determine PHE concentrations. The mean concentrations of Mn in shoots and Fe in the roots of rice grown on the flooded tailings were 2140mgkg-1 and 15,219mgkg-1, respectively. Mn was extensively translocated from roots to shoots (translocation factor (TF) = 2). Conversely, Fe accumulated in roots (TF = 0.015) and caused morphological damage to this rice organ. The application of macro and micronutrients lessened Fe toxicity in the roots of rice cultivated on the flooded tailings. The flooding of tailings influenced more Fe accumulation than Mn accumulation by rice plants. The PHE Ag, As, Cd, Ni, Hg, Pb, and Sb exhibited low total concentrations (maximum of 9mgkg-1 for Ni and a minimum of 0.2mgkg-1 for Cd, Hg, and Sb), and it was not observed an increase in their availability under tailings flooding conditions.

Role of transcription factor complex OsbHLH156-OsIRO2 in regulating manganese, copper, and zinc transporters in rice.

Iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) are essential micronutrients that are necessary for plant growth and development, but can be toxic at supra-optimal levels. Plants have evolved a complex homeostasis network that includes uptake, transport, and storage of these metals. It was shown that the transcription factor (TF) complex OsbHLH156-OsIRO2 is activated under Fe deficient conditions and acts as a central regulator on Strategy II Fe acquisition. In this study, the role of the TF complex on Mn, Cu, and Zn uptake was evaluated. While Fe deficiency led to significant increases in shoot Mn, Cu, and Zn concentrations, the increases of these divalent metal concentrations were significantly suppressed in osbhlh156 and osiro2 mutants, suggesting that the TF complex plays roles on Mn, Cu, and Zn uptake and transport. An RNA-sequencing assay showed that the genes associated with Mn, Cu, and Zn uptake and transport were significantly suppressed in the osbhlh156 and osiro2 mutants. Transcriptional activation assays demonstrated that the TF complex could directly bind to the promoters of OsIRT1, OsYSL15, OsNRAMP6, OsHMA2, OsCOPT1/7, and OsZIP5/9/10, and activate their expression. In addition, the TF complex is required to activate the expression of nicotianamine (NA) and 2'-deoxymugineic acid (DMA) synthesis genes, which in turn facilitate the uptake and transport of Mn, Cu, and Zn. Furthermore, OsbHLH156 and OsIRO2 promote Cu accumulation to partially restore the Fe-deficiency symptoms. Taken together, OsbHLH156 and OsIRO2 TF function as core regulators not only in Fe homeostasis, but also in Mn, Cu, and Zn accumulation.

Characterization of Metal Tolerance Proteins and Functional Analysis of GmMTP8.1 Involved in Manganese Tolerance in Soybean.

Manganese is an essential micronutrient for plant growth but can be toxic to plants when it reaches excessive levels. Although metal tolerance proteins (MTPs), which belong to the cation diffusion facilitator (CDF) family, have been demonstrated to play critical roles in manganese (Mn) tolerance in plants, the characteristics and functions of GmMTP members in the response of soybean (Glycine max) to Mn toxicity have not been documented. In this study, growth inhibition was observed in soybean plants that were exposed to a toxic level of Mn in hydroponics, as reflected by the generation of brown spots, and decreased leaf chlorophyll concentration and plant fresh weight. Subsequent genome-wide analysis resulted in the identification of a total of 14 GmMTP genes in the soybean genome. Among these GmMTPs, 9 and 12 were found to be regulated by excess Mn in leaves and roots, respectively. Furthermore, the function of GmMTP8.1, a Mn-CDF homologue of ShMTP8 identified in the legume Stylosanthes hamata that is involved in Mn detoxification, was characterized. Subcellular localization analysis showed that GmMTP8.1 was localized to the endoplasmic reticulum (ER). Heterologous expression of GmMTP8.1 led to the restoration of growth of the Mn-hypersensitive yeast (Saccharomyces cerevisiae) mutant Δpmr1, which is made defective in Mn transport into the Golgi apparatus by P-type Ca/Mn-ATPase. Furthermore, GmMTP8.1 overexpression conferred tolerance to the toxic level of Mn in Arabidopsis (Arabidopsis thaliana). Under excess Mn conditions, concentrations of Mn in shoots but not roots were decreased in transgenic Arabidopsis, overexpressing GmMTP8.1 compared to the wild type. The overexpression of GmMTP8.1 also led to the upregulation of several transporter genes responsible for Mn efflux and sequestration in Arabidopsis, such as AtMTP8/11. Taken together, these results suggest that GmMTP8.1 is an ER-localized Mn transporter contributing to confer Mn tolerance by stimulating the export of Mn out of leaf cells and increasing the sequestration of Mn into intracellular compartments.

The Combined Effect of ZnO and CeO2 Nanoparticles on Pisum sativum L.: A Photosynthesis and Nutrients Uptake Study.

Cerium oxide nanoparticles (CeO2 NPs) and zinc oxide nanoparticles (ZnO NPs) are emerging pollutants that are likely to occur in the contemporary environment. So far, their combined effects on terrestrial plants have not been thoroughly investigated. Obviously, this subject is a challenge for modern ecotoxicology. In this study, Pisum sativum L. plants were exposed to either CeO2 NPs or ZnO NPs alone, or mixtures of these nano-oxides (at two concentrations: 100 and 200 mg/L). The plants were cultivated in hydroponic system for twelve days. The combined effect of NPs was proved by 1D ANOVA augmented by Tukey’s post hoc test at p = 0.95. It affected all major plant growth and photosynthesis parameters. Additionally, HR-CS AAS and ICP-OES were used to determine concentrations of Cu, Mn, Fe, Mg, Ca, K, Zn, and Ce in roots and shoots. Treatment of the pea plants with the NPs, either alone or in combination affected the homeostasis of these metals in the plants. CeO2 NPs stimulated the photosynthesis rate, while ZnO NPs prompted stomatal and biochemical limitations. In the mixed ZnO and CeO2 treatments, the latter effects were decreased by CeO2 NPs. These results indicate that free radicals scavenging properties of CeO2 NPs mitigate the toxicity symptoms induced in the plants by ZnO NPs.

The Protective Biochemical Properties of Arbuscular Mycorrhiza Extraradical Mycelium in Acidic Soils Are Maintained throughout the Mediterranean Summer Conditions

In acidic soils with manganese (Mn) toxicity, arbuscular mycorrhizal fungi (AMF) can improve plant host growth by enhancing nutrition and protecting against environmental stress. The intact extraradical mycelium (ERM) of AMF is able to survive Mediterranean summer conditions and provide an earlier colonization of winter crops. This study evaluated if summer season conditions hindered the beneficial effects of wheat colonization by the intact ERM associated with a native plant, in acidic soil. Wheat was grown in soil with intact or disrupted ERM associated with Ornithopus compressus (ORN), developed for 7 or 24 weeks, to simulate ERM summer survival. The activity of antioxidant enzymes was determined, and the quantitative analysis of Mn and macronutrients was performed by inductively coupled plasma mass spectrometry (ICP-MS), in wheat shoots and respective subcellular fractions. Wheat colonization by intact ERM decreased shoot Mn concentration but increased the proportion of Mn in the apoplast. Overall, antioxidant enzymatic activity decreased but the proportion of Mn-superoxide dismutase activity over the remaining isoforms increased, suggesting its important role in the AMF-mediated mitigation of Mn toxicity. Summer conditions did not substantially reduce the benefits provided by ORN ERM. A no-till strategy allied to the development of native microbiota can contribute to the sustainable optimization of acidic soil use.

Effects of Municipal Solid Waste Compost Supplemented with Inorganic Nitrogen on Physicochemical Soil Characteristics, Plant Growth, Nitrate Content, and Antioxidant Activity in Spinach

In this study, we evaluated the effects of municipal solid waste compost supplemented with inorganic N on the physicochemical properties of soil, plant growth, nitrate concentration, and antioxidant activity in spinach. Experiments were carried out in neutral and acidic soils that were low in organic matter. A fertilized soil was used as a control, while four compost treatments—two compost rates of 35 and 70 t ha−1, supplemented or not with inorganic N (92 kg N ha−1 as Ca (NO3)2)—were applied by fertigation. The addition of compost increased the soil organic matter content and pH in both soils. The compost supplementation with N greatly increased the shoot dry weight and spinach fresh yield by nearly 109%. With the highest compost rate and 43% N applied, the yield increased in both soils, similar to results obtained in fertilized soil (3.8 kg m−2). The combined application of compost and N could replace inorganic P and K fertilization to a significant extent. The compost application at both rates and in both soils considerably decreased shoot Mn concentrations.

Comparative Response of Two Rice (Oryza sativa L.) Cultivars to Applied Zinc and Manganese for Mitigation of Salt Stress

Soil salinity, together with zinc (Zn) and manganese (Mn) deficiencies, adversely affects rice growth and yield. The comparative salinity stress mitigation response of rice to Zn or Mn remains largely unknown. Rice cultivars, viz. Basmati-515 and KSK-282, were grown in saline soil having electrical conductivity (EC) of 7.5 dS m−1 (as control) parallel to EC 7.5 dS m−1 + Zn 3.5 mg kg−1 and EC 7.5 dS m−1 + Mn 3.5 mg kg−1 treatments in a pot experiment. Application of Zn in saline soil decreased (p < 0.05) sodium (Na+) and chloride (Cl−) concentrations (6% and 26%, respectively) and increased potassium (K+) concentration (25.9%) in leaves compared with the control. The increments in superoxide dismutase (SOD), glutathione reductase (GR), and catalase activities (CAT) reduced salinity-induced oxidative damage which translated into 50.5% and 74% increased membrane stability index (MSI) and relative water content (RWC), respectively. A 5-fold increment of Zn in soil solution ensured its adequate availability for rice which increased SPAD value for an effective photosynthesis to reinforce above ground biomass and grain production. The enhancements in indole-3-acetic acid (46% and 39%) whereas reductions in abscisic acid (18% and 11%) in shoot and root highlighted the Zn-dependent mitigation of salinity stress in both rice cultivars. Ameliorative effect of Mn remained second to Zn despite the increased shoot Mn concentration in KSK-282. Conclusively, both rice cultivars preferred Zn to mitigate salinity; however, KSK-282 responded better through increased antioxidant activities, indole-3-acetic acid biosynthesis, and decreased abscisic acid accumulation.

Title: Excess Zn-induced changes in physiological parameters and expression levels of TaZips in two wheat genotypes

Zinc (Zn) is an important higher plant micronutrient; however, high amounts of Zn in soil may negatively affect plant growth. In this study, two wheat (Triticum aestivum L.) genotypes [Aikang58 (AK) and Zhengmai0856 (ZM)] were grown in nutrient solutions containing various Zn concentrations and were characterized using physiological and molecular approaches. Compared to sufficient Zn supply (0.25 mg L−1), excess Zn (2.5 mg L−1) significantly decreased the biomass and root morphological features (root length, volume, and surface area) of AK, whereas only a slight decrease was observed in ZM. ZM maintained higher Zn concentration and translocation factor, and lower net photosynthetic rate than AK under excess Zn supply. Excess Zn decreased Cu, Fe, and Mn concentrations in roots of both wheat genotypes, whereas Mn concentrations in shoots increased. In addition, the expression of TaZIPs indicated that TaZIP5, −6, and −13 in roots are primarily involved in Zn uptake when the medium has elevated Zn levels. The translocation of more Zn from the roots to shoots facilitates in maintaining the efficiency of photosynthesis by using lower amounts of photosynthetic pigments, and TaZIP genes involved in cell ion homeostasis contributes to greater Zn tolerance in ZM than AK.

You are here: Home » Online First » Volume 15, 2020 - Number 1 » EFFECT OF SUBSTRATE PROPERTIES ON THE MOBILITY OF SELECTED TRACE ELEMENTS IN SOIL AND CONCENTRATIONS IN SHOOTS OF PHALARIS ARUNDINACEA, Carpathian Journal of Earth and Environmental Sciences, February 2020, Vol. 15, No. 1, p. 49 - 56; DOI:10.26471/cjees/2020/015/108 « Back Christin MOSCHNER1, Ulf FEUERSTEIN2, Hermann

Christin MOSCHNER, Ulf FEUERSTEIN, Hermann HEILMEIER, Nazia ZAFFAR & Oliver WICHE - EFFECT OF SUBSTRATE PROPERTIES ON THE MOBILITY OF SELECTED TRACE ELEMENTS IN SOIL AND CONCENTRATIONS IN SHOOTS OF PHALARIS ARUNDINACEA, Carpathian Journal of Earth and Environmental Sciences, February 2020, Vol. 15, No. 1, p. 49 - 56; DOI:10.26471/cjees/2020/015/108

Influence of poultry manure and its biochar, Funneliformis mosseae and salinity stress on corn yield and micronutrients concentration

Direct use of poultry manure (PM) as an organic fertilizer in agriculture may cause environmental concerns; therefore, application of its biochar might be an effective solution. A greenhouse experiment was conducted to investigate the influence of PM and its biochar (PMB) (control, 1% and 2% PM (w/w), 1% and 2% (W/W) PMB) on the growth and micronutrients concentration of corn under salinity stress (0.5, 3.6, 7.9 and 12.4 dS m-1) in the presence or absence of arbuscular mycorrhizal fungus (AMF) (Funneliformis mosseae). Results indicated that application of PM and PMB significantly increased corn shoot dry weight (SDW) compared to that of control in non-AMF plants. However, SDW was higher in PMB application compared to that of PM by 15% and 8% for 1% and 2% (w/w) application rates, respectively. In AMF-plants, addition of 2% PMB had no significant effect on SDW compared to that of control. Hence, co-application of PMB (2%), and AMF did not increase SDW due to the fact that AMF was ineffective to enhance corn yield (at high phosphorous (P) concentration in 2% PMB rate). Salinity stress, at low levels (3.6 and 7.9 dS m-1), increased SDW of corn but at a higher level (12.4 dS m-1), decreased it significantly, in both non-AMF and AMF plants. In general, shoot micronutrients concentration (except for Cu) significantly increased along with increasing soil ECe levels in AMF and AMF plants. In non-AMF plants, only addition of 2% PMB increased shoot Mn concentration by 20% compared to that of control. However, in AMF plants, application of PM (2%) and PMB (1% and 2%) decreased Mn concentration by 27%, 16%, and 9% compared to those of control treatment, respectively. Poultry manure biochar increased corn shoot Zn, Cu and Fe concentrations compared to those of control due to the higher concentration of these nutrients in biochar compared to PM. In conclusion, pyrolysis of PM almost eliminated foul odor of PM and increased dry matter yield of corn.

Polyamines (spermidine and putrescine) mitigate the adverse effects of manganese induced toxicity through improved antioxidant system and photosynthetic attributes in Brassica juncea

Polyamines (PAs) are recognized as plant growth regulators that are involved in the stress management in various crops. In the current study, mitigative roles of spermidine (Spd) and putrescine (Put) were assessed in manganese (Mn) stressed Brassica juncea plants. Spd or Put (1.0 mM) were applied to the foliage of Brassica juncea at 35 days after sowing (DAS) grown in the presence of Mn (30 or 150 mg kg−1 soil). The higher level of Mn (150 mg kg−1) diminished photosynthetic attributes and growth, enhanced the production of reactive oxygen species (ROS) like hydrogen peroxide (H2O2) and superoxide anion (O2·−) content, affected stomatal movement and increased the Mn concentration in roots and shoots of the plant at 45 DAS, whereas it enhanced the activities of various antioxidant enzymes and proline content in the foliage of Brassica juncea plants. On the other hand, treatment of PAs (Spd or Put) to Mn stressed as well as non-stressed plants resulted in a remarkable improvement in the stomatal behaviour, photosynthetic attributes, growth and biochemical traits, decreased the production of ROS (H2O2 and O2·−) and concentration of Mn in different parts of plant. It is concluded that out of the two polyamines (Spd or Put), Spd proved more efficient and enhanced growth, photosynthesis, and metabolic state of the plants which bestowed tolerance and helped the plants to cope efficiently under Mn stress.

Potential of vermicompost and limestone in reducing copper toxicity in young grapevines grown in Cu-contaminated vineyard soil

Foliar fungicide application in grapevines increases the content of heavy metals such as copper (Cu) in vineyard soils, which may reach phytotoxic levels. The application of soil amendments such as limestone and vermicompost may reduce Cu availability and phytotoxicity. The study aimed to assess growth, physiological status and changes in root morphology in young grapevines grown for 12 months in Cu-contaminated soil with and without the application of soil amendments. Samples of a Typic Hapludalf soil were collected in a vineyard with more than 30 years of cultivation. The following treatments were used: 1) control (without amendment), 2) application of organic vermicompost (86.7 g kg−1) and 3) application of limestone (3 Mg ha−1). Grapevines (Paulsen 1103 rootstock) were transplanted and grown for 12 months in PVC soil columns. We assessed parameters of growth, photosynthesis and root morphology. Grapevines grown in soil treated with limestone showed increased growth, dry matter yield and photosynthetic efficiency. The highest Cu concentrations in root tissue were found in grapevines grown in control soil. The application of vermicompost in this study did not alleviate Cu toxicity. Grapevines grown in soil treated with vermicompost showed high manganese (Mn) concentration in shoots before the winter pruning, reflecting the high Mn concentrations in soil solution that caused Mn phytotoxicity, resulting in plant death after the winter pruning. The vermicompost used in this study is not suitable for agronomic use. The use of limestone was an effective strategy to reduce Cu availability and phytotoxicity.

Timing of Waterlogging Is Crucial for the Development of Micronutrient Deficiencies or Toxicities in Winter Wheat and Rapeseed

Waterlogging events affect soil properties, which alter plant nutrient availability and result in an increased solubility of micronutrients. Until now, it has not been conclusively determined whether plants take up increased concentrations of plant-available Mn, Fe, Cu, or Zn during a period of waterlogging. The aim of this study was to analyze (1) if the micronutrient concentrations increase in plant tissues after waterlogging or (2) rather lead to micronutrient deficiencies, and (3) if this process depends on the developmental stage in which the plant was flooded. Winter wheat and rapeseed were cultivated in large containers and water-logged at two developmental stages: DC 31 (first node visible) and DC 51 (beginning of ear emergence/floral bud appearance). Early waterlogging did not result in microelement toxicities neither in winter wheat nor in rapeseed, although the Mn concentration in rapeseed shoots was significantly increased. On the contrary, in rapeseed, early waterlogging resulted in significantly decreased Cu and Zn concentrations. After late waterlogging, plants accumulated high amounts of Mn and Fe (wheat) or Mn, Cu, and Zn (rapeseed), leading to toxic levels. We conclude that the occurrence of micronutrient deficiencies or toxicities depends on the developmental stage in which the plant was flooded.

Expression of TpNRAMP5, a metal transporter from Polish wheat (Triticum polonicum L.), enhances the accumulation of Cd, Co and Mn in transgenic Arabidopsis plants.

TpRNAMP5 is mainly expressed in the plasma membrane of roots and basal stems. It functions as a metal transporter for Cd, Mn and Co accumulation. Numerous natural resistance-associated macrophage proteins (NRAMPs) have been functionally identified in various plant species, including Arabidopsis, rice, soybean and tobacco, but no information is available on NRAMP genes in wheat. In this study, we isolated a TpNRAMP5 from dwarf Polish wheat (DPW, Triticum polonicum L.), a species with high tolerance to Cd and Zn. Expression pattern analysis revealed that TpNRAMP5 is mainly expressed in roots and basal stems of DPW. TpNRAMP5 was localized at the plasma membrane of Arabidopsis leaf protoplast. Expression of TpNRAMP5 in yeast significantly increased yeast sensitivity to Cd and Co, but not Zn, and enhanced Cd and Co concentrations. Expression of TpNRAMP5 in Arabidopsis significantly increased Cd, Co and Mn concentrations in roots, shoots and whole plants, but had no effect on Fe and Zn concentrations. These results indicate that TpNRAMP5 is a metal transporter enhancing the accumulation of Cd, Co and Mn, but not Zn and Fe. Genetic manipulation of TpNRAMP5 can be applied inthe future to limit the transfer of Cd from soil to wheat grains, thereby protecting human health.

Genome-wide association study to identify candidate loci and genes for Mn toxicity tolerance in rice.

Manganese (Mn) is an essential micro-nutrient for plants, but flooded rice fields can accumulate high levels of Mn2+ leading to Mn toxicity. Here, we present a genome-wide association study (GWAS) to identify candidate loci conferring Mn toxicity tolerance in rice (Oryza sativa L.). A diversity panel of 288 genotypes was grown in hydroponic solutions in a greenhouse under optimal and toxic Mn concentrations. We applied a Mn toxicity treatment (5 ppm Mn2+, 3 weeks) at twelve days after transplanting. Mn toxicity caused moderate damage in rice in terms of biomass loss and symptom formation despite extremely high shoot Mn concentrations ranging from 2.4 to 17.4 mg g-1. The tropical japonica subpopulation was more sensitive to Mn toxicity than other subpopulations. Leaf damage symptoms were significantly correlated with Mn uptake into shoots. Association mapping was conducted for seven traits using 416741 single nucleotide polymorphism (SNP) markers using a mixed linear model, and detected six significant associations for the traits shoot manganese concentration and relative shoot length. Candidate regions contained genes coding for a heavy metal transporter, peroxidase precursor and Mn2+ ion binding proteins. The significant marker SNP-2.22465867 caused an amino acid change in a gene (LOC_Os02g37170) with unknown function. This study demonstrated significant natural variation in rice for Mn toxicity tolerance and the possibility of using GWAS to unravel genetic factors responsible for such complex traits.

Responses of contrasting rice genotypes to excess manganese and their implications for lignin synthesis

Manganese (Mn) toxicity is frequently encountered in crops grown on soils with low pH or low redox potential, and harmful to plant development and growth. This study aimed at exploring adaptive mechanisms to Mn toxicity in rice, and investigated the effects of Mn toxicity on shoot lignification. Sixteen rice genotypes were grown in hydroponic solutions and exposed to normal (0.5 mg dm−3) or toxic (5 mg dm−3) Mn concentrations for three weeks. Morphological responses to Mn toxicity included a significant reduction in shoot length and the formation of visible symptoms scored as leaf damage index (LDI). Based on shoot Mn concentrations in the Mn toxic treatment, genotypes were classified as Mn includers and excluders. Across different genotypes, shoot Mn concentrations were significantly negatively correlated with relative shoot length and positively correlated with LDI. Consequently, the most tolerant genotypes in terms of morphology were all excluders, while the most sensitive genotypes were includers. The sensitive genotypes were also more responsive to manganese in terms of lipid peroxidation than tolerant genotypes. Shoots of rice plants grown in the high Mn treatment showed a higher level of lignification measured as thioglycolic acid lignin (TGAL), especially among Mn includers. TGAL was positively correlated with shoot Mn concentration and the levels of phenolics. In contrast, peroxidase activity was not responsive to the Mn treatment and was not significantly correlated with shoot lignification. In conclusion, exclusion is a dominant tolerance mechanism to Mn toxicity in rice. Further, Mn stimulated lignin biosynthesis in rice, especially in genotypes that were unable to exclude Mn.

The iron-regulated transporter 1 plays an essential role in uptake, translocation and grain-loading of manganese, but not iron, in barley.

Transporters involved in manganese (Mn) uptake and intracellular Mn homeostasis in Arabidopsis and rice are well characterized, while much less is known for barley, which is particularly prone to Mn deficiency. In this study we have investigated the role of the iron-regulated transporter 1 (IRT1) for Mn uptake and translocation in barley plants. We employed an RNAi approach to reduce HvIRT1 expression to 5% of the wild-type level. This enabled characterization of the functional role of HvIRT1 by use of advanced imaging and phenotyping techniques applied to plants growing in hydroponics or soils with different Mn availability. Our results highlight the importance of HvIRT1 for the transport of Mn across the root endodermis into the stele. In the hvirt1-RNAi lines, a chlorotic phenotype with reduced shoot Mn concentration and impaired photosynthetic functionality was observed, especially under conditions with low Mn availability. We also document that HvIRT1 controlled the Mn distribution within the barley grain. Surprisingly, unlike other IRT1 orthologues, HvIRT1 played no significant role in iron uptake. We conclude that the barley IRT1 orthologue has a novel function with respect to ensuring sufficient shoot Mn concentrations. The preference of IRT1 for Mn instead of Fe is discussed in an evolutionary context.

Vascular plants as ecological indicators of metals in alpine vegetation (Karkonosze, SW Poland).

Calluna vulgaris, Carex rigida, Deschampsia flexuosa, Nardus stricta and Vaccinium myrtillus are abundant in the vegetation of mountainous areas in Northern and Central Europe. Knowledge of their ability to accumulate increased amounts of metals could be useful in the evaluation of environmental pollution in the alpine tundra of high mountains. Additionally, this investigation may contribute to understanding the rate and direction of recent vegetation change in Karkonosze and similar types of environments. Our investigation revealed that Carex rigida, C. vulgaris and V. myrtillus contain excessive Mn concentrations in shoots with the highest BF for this element compared to the BFs of other elements. C. rigida, with Cu, Mn and Zn concentrations exceeding the toxicity thresholds for plants, seems to be the best metal phytoaccumulator for Nardus stricta grasslands Carici (rigidae)-Nardetum (CrN) and alpine heathlands Carici (rigidae)-Festucetum airoidis (CrFa) associations in the Karkonosze. Based on relevant BFs >1, it can be stated that the following plant available metals were transferred to shoots: Cu, Mn and Ni by C. vulgaris; Cd, Cu, Mn, Ni and Zn by C. rigida; Cd, Cu, Mn, Ni and Zn by D. flexuosa; Cu, Mn, Ni and Zn by N. stricta and Cu, Mn and Zn by V. myrtillus.

Effect of biochar on cadmium bioavailability and uptake in wheat (Triticum aestivum L.) grown in a soil with aged contamination

Cadmium (Cd) is a well-known and widespread toxic heavy metal while the effects of biochar (BC) on Cd bioavailability and toxicity in wheat, especially in soils with aged contamination are largely unknown. In the present study, the effect of rice straw BC on Cd immobilization in soil and uptake by wheat in an agricultural contaminated-soil was investigated. Different levels of rice straw BC (0%, 1.5%, 3.0% and 5% w/w) were incorporated into the soil and incubated for two weeks. After this, wheat plants were grown in the amended soil until maturity. The results show that the BC treatments increased the soil and soil solution pH and silicon contents in the plant tissues and in the soil solution while decreased the bioavailable Cd in soil. The BC application increased the plant-height, spike-length, shoot and root dry mass and grain yield in a dose additive manner when compared with control treatment. As compared to control, BC application increased the photosynthetic pigments and gas exchange parameters in leaves. Biochar treatments decreased the oxidative stress while increased the activities of antioxidant enzymes in shoots compared to the control. The BC treatments decreased the Cd and Ni while increased Zn and Mn concentrations in shoots, roots, and grains of wheat compared to the control. As compared to the control, Cd concentration in wheat grains decreased by 26%, 42%, and 57% after the application of 1.5%, 3.0%, and 5.0% BC respectively. Overall, the application of rice straw BC might be effective in immobilization of metal in the soil and reducing its uptake and translocation to grains.

Physiological and biochemical responses to manganese toxicity in ryegrass (Lolium perenne L.) genotypes

We studied resistance to manganese (Mn) toxicity under acidic conditions and its relationship with nutrients such as calcium (Ca) and magnesium (Mg) in new perennial ryegrass (Lolium perenne L.) genotypes (One-50, Banquet-II and Halo-AR1) introduced in southern Chile, using the Nui genotype as the reference. Plants were grown in nutrient solution at increased Mn concentrations (0–750 μM) at pH 4.8, and physiological and biochemical features were determined. Under higher Mn concentration, the One-50 genotype had a significantly lower relative growth rate (RGR) of shoots and roots, whereas in the other cultivars this parameter did not change under variable Mn treatments. Increasing the Mn concentration led to an increased Mn concentration in roots and shoots, with Banquet-II and Halo-AR1 having higher Mn in roots than shoots. Shoot Mg and Ca concentrations in all genotypes (except Banquet-II) decreased concomitantly with increasing Mn applications. In contrast to the other genotypes, Banquet-II and Halo-AR1 maintained their net CO2 assimilation rate regardless of Mn treatment, whereas the chlorophyll concentration decreased in all genotypes with the exception of Banquet-II. In addition, lipid peroxidation in Banquet-II roots increased at 150 μM Mn, but decreased at higher Mn concentrations. This decrease was associated with an increase in antioxidant capacity as well as total phenol concentration. Banquet-II and Halo-AR1 appear to be the most Mn-resistant genotypes based on RGR and CO2 assimilation rate. In addition, Mn excess provoked a strong decrease in Ca and Mg concentrations in shoots of the Mn-sensitive genotype, whereas only slight variations in the Mn-resistant genotype were noted. When other evaluated parameters were taken into account, we concluded that among the perennial ryegrass genotypes introduced recently into southern Chile Banquet-II appears to be the most Mn-resistant, followed by Halo-AR1, with One-50 being the most sensitive.