Aluminum Toxicity

Th e Cerrado is the largest savanna of South America and its physiognomy varies from savanna to woodlands. Th ere are two main types of woodlands in the Cerrado: dystrophic woodlands, dominated by N-fi xing leguminous trees (LEG), and mesotrophic woodlands dominated by non-leguminous drought-tolerant trees (DRY), which are calcicoles and sensitive to Al 3+ . Th e working hypothesis is that LEG and DRY are functional antagonists in terms of the acidifi cation/alkalization processes involving diff erent forms of inorganic nitrogen and pH, Ca 2+ and Al 3+ in soil. Tree species basal area and soil properties were used to investigate the antagonism between LEG and DRY using generalized linear models. Th e results suggest that LEG and DRY are antagonists. Th e LEG were positively associated with Al 3+ , NO 3-and NH 4+ content and negatively related to increasing Ca 2+ content, whereas the DRY were negatively associated with Al 3+ , NO 3-and NH 4+ and positively associated with increasing Ca 2+ content. Th e upper soil layer in plots dominated by LEG species became more acidic and the upper soil layer in plots dominated by DRY species became more alkaline. Th e results suggest that LEG and DRY are functional antagonists and their preferences for NH 4+ or NO 3-might infl uence the way the Cerrado woodland changes.

Context: Populus nigra L., is a species of cottonwood poplar that belongs to the Salicaceae family, is cultivated in multiple areas in Algeria, with an Algerian name of Safsaf. Aims: To evaluate the Populus nigra flower buds extract for its effects on brain modifications against aluminum-induced neurotoxicity in mice. The hypouricemic action of the extract was also evaluated. Methods: To evaluate the effect of extract on AlCl3-induced neurotoxicity on mice a battery of tests was performed to assess a spectrum of learning and memory functions. The hypouricemic action of the extract was studied by the measure of uric acid levels and liver xanthine oxidoreductase activity in normal and hyperuricemic mice. Results: Co-administration of P. nigra extract (200 mg/kg) and AlCl3 (100 mg/kg/day) combined with D-galactose (200 mg/kg/day) during four weeks was found to antagonize the harmful effects of AlCl3 by restoring all the test parameters. Moreover, extract restored the pyramidal cells to...

This review paper of literature highlights the role of accumulation of aluminum in tea leaves and its toxic effects on human health. Tea is the most consumed beverage in the world after water and contains heavy metals and trace elements that may cause potential negative effects on health. Tea is known to be a metal accumulator. However, drinking even a very high dietary amount of black tea or green tea would be unlikely to cause these adverse effects in humans. Thus, for the majority of heavy tea drinkers around the world, tea is likely to be the largest single source of aluminum intake. Addition of milk to tea can decrease or completely inhibit tea antioxidant properties. According to the literature survey, it is well known that the tea plant accumulates aluminum in its leaves to a greater extent than most other edible plants, and would be a potentially important source of dietary aluminum. Aluminum can be transferred into tea infusions through brewing tea, then enter the human body via tea drinking, thereby causing potential harm to human health. On the basis of literature survey, even though some epidemiological reports were contradictory, there was mounting scientific evidence suggesting a relationship between the neurotoxicity of aluminum and the pathogenesis of Alzheimer's disease. In particular, the link between aluminum and Alzheimer's disease has been the subject of scientific debate for several decades. The literature survey confirmed that aluminum hypothesis has been the subject of much debate and criticism for several decades. Evidence from human clinical trials suggested that moderate (1-6 cups/day) rather than excessive consumption of tea could bring diverse health benefits. The relationship between tea consumption and dementia has not been well established yet and other studies reported no significant association. The cause of Alzheimer's disease and any association with aluminum is still unknown. There have been conflicting findings in the scientific literature.

Fine roots constitute a significant component of the net primary productivity (NPP) of forest ecosystems but are much less studied than aboveground NPP. Comparisons across sites and regions are also hampered by inconsistent methodologies, especially in tropical areas. Here, we present a novel dataset of fine root biomass, productivity, residence time, and allocation in tropical old‐growth rainforest sites worldwide, measured using consistent methods, and examine how these variables are related to consistently determined soil and climatic characteristics. Our pantropical dataset spans intensive monitoring plots in lowland (wet, semi‐deciduous, and deciduous) and montane tropical forests in South America, Africa, and Southeast Asia (n = 47). Large spatial variation in fine root dynamics was observed across montane and lowland forest types. In lowland forests, we found a strong positive linear relationship between fine root productivity and sand content, this relationship was even stro...

RESUMO: O objetivo deste trabalho foi identificar e quantificar os ácidos graxos nos grãos de café de cultivares resistentes à ferrugem, e verificar se existem alterações nesta composição, em função das condições ambientais. Para tanto se avaliou a composição de ácidos graxos de 7 cultivares de C. arabica portadores de resistência a ferrugem desenvolvidas pelo Programa de Melhoramento Genético coordenado pela Epamig em parceria com a UFV e a UFLA e duas cultivares suscetíveis (Bourbon Amarelo e Topázio MG1190) como testemunhas para padrão de bebida em dois ambientes de cultivo: Lavras, na região Sul de Minas e Patrocínio, na região Cerrado de Minas. Houve diferença significativa entre as cultivares avaliadas para a maioria dos ácidos graxos, exceto para os ácidos esteárico e oleico. O conteúdo de ácido palmítico, palmitoleico, linoleico e linolênico permitiu a diferenciação dos ambientes estudados a partir do teste F a p<0,05, e houve diferença significativa também para as interações entre as nove cultivares e os dois ambientes. Identificou-se a presença de um ácido graxo incomum para café, o ácido gamma-linolênico (C18:3 ω-6).

Objective: The aim of the current investigation is to evaluate or discover the right combination with less or no side effect to treat the inflammatory bowel disease. Method: Male Sprague Dawley (S.D) rats (250gm) was randomly allocated to 17 groups (n=6): Group I received water throughout the 18 day study period, groups II and III only were received 0.1 mL 3% N-ethylmaleimide (NEM) and  0.1mL of 1% methyl cellulose intracolonically at 11 days of the study, respectively. Group-IV to XVII were received selected drug and drug combination throughout 18 days as well as at 11 th day also receive 0.1mL 3% N-ethylmaleimide (prepared in 1% methylcellulose). The histopathological features of NEM model control animal included surface epithelial damage, mucosal crypt drop out, edema, desquamated areas and diffuse inflammatory cell infiltration in the mucosa. Result: Pretreatments of selected drug/s significantly attenuated the extent and severity of the histological signs of cell damage also pr...

World Agriculture faces daunting challenges in feeding the growing population today. Reduction in arable land extent due to numerous reasons threatens achievement of food and nutritional security. Under this back ground, agricultural use of acidic soils, which account for approximately 40 % of the world arable lands is of utmost important. However, due to aluminum (Al) toxicity and low available phosphorous (P) content, crop production in acidic soils is restricted. Citrus, in this context, gains worldwide recognition as a crop adapted to harsh environments. The present paper reviewed Al toxicity and possible toxicity alleviation tactics in citrus. As reported for many other crops, inhibition of root elongation, photosynthesis and growth is experienced in citrus also due to Al toxicity. Focusing at toxicity alleviation, interaction between boron (B) and Al as well as phosphorus and Al has been discussed intensively. Al toxicity in citrus could be alleviated by P through increasing immobilization of Al in roots and P level in shoots rather than through increasing organic acid secretion, which has been widely reported in other crops. Boron-induced changes in Al speciation and/or sub-cellular compartmentation has also been suggested in amelioration of root inhibition in citrus. Despite the species-dependent manner of response to Al toxicity, many commercially important citrus species can be grown successfully in acidic soils, provided toxicity alleviation Agro-biological tactics such as addition of phosphorous fertilizers are used properly.

Fine roots constitute a significant component of the net primary productivity (NPP) of forest ecosystems but are much less studied than aboveground NPP. Comparisons across sites and regions are also hampered by inconsistent methodologies, especially in tropical areas. Here, we present a novel dataset of fine root biomass, productivity, residence time, and allocation in tropical old‐growth rainforest sites worldwide, measured using consistent methods, and examine how these variables are related to consistently determined soil and climatic characteristics. Our pantropical dataset spans intensive monitoring plots in lowland (wet, semi‐deciduous, and deciduous) and montane tropical forests in South America, Africa, and Southeast Asia (n = 47). Large spatial variation in fine root dynamics was observed across montane and lowland forest types. In lowland forests, we found a strong positive linear relationship between fine root productivity and sand content, this relationship was even stro...

In this work, the efficacy of two different strategies, used for 20 years (1992–2012) to restore a lignite mine dump, was investigated. The reclamation strategies were selection of the sterile materials, avoiding surface placement of pyritic materials, or surface application of topsoil material. Representative plots corresponding to each of both strategies were selected, as well as a control plot where reclamation techniques were not applied. An increase in total C, soluble Al, and exchangeable Al, as well as a decrease in pH, electrical conductivity, sulfate, and exchangeable cations concentrations took place during the study period. Avoiding pyritic materials on surface was the strategy giving the best acid–base conditions in the whole period, showing higher pH values (6.1–6.7) than application of topsoil (4.7–5.3), as well as the highest exchangeable Ca values (0.71–6.83 vs. 0.55–3.00 cmol(+) kg−1), and less exchange Al (0.22–2.80 vs. 0.99–3.72 cmol(+) kg−1) and soluble Al (0.04–...

SummaryThe phytotoxic effects of aluminum (Al) on root systems of crop plants constitute a major agricultural problem in many areas of the world. Root exudation of Al‐chelating molecules such as low‐molecular‐weight organic acids has been shown to be an important mechanism of plant Al tolerance/resistance. Differences observed in the physiology and electrophysiology of root function for two maize genotypes with contrasting Al tolerance revealed an association between rates of Al‐activated root organic acid release and Al tolerance. Using these genotypes, we cloned ZmALMT1, a maize gene homologous to the wheat ALMT1 and Arabidopsis AtALMT1 genes that have recently been described as encoding functional, Al‐activated transporters that play a role in tolerance by mediating Al‐activated organic acid exudation in roots. The ZmALMT1 cDNA encodes a 451 amino acid protein containing six transmembrane helices. Transient expression of a ZmALMT1::GFP chimera confirmed that the protein is target...

Tissue concentrations of A1 in red and Norway spruce trees were compared across 5 sites in North America and Europe as part of an investigation of A1 biogeochemistry in forested ecosystems (ALBIOS). Fine roots and foliage were sampled and analyzed for A1, Ca, Mg, and P, and the chemistry of soil and soil solutions was characterized at each plot by horizon. Sites exhibited a wide range in soil AI saturation and in concentrations of A1 and sulfate in lysimeter solutions. Aluminium concentrations in roots were two orders of magnitude higher than those in foliage. Fine roots (< 1.0 mm) from B horizons had the highest A1 concentrations and appeared to be the best phytoindicators of plant-available A1. Aluminium concentrations in free roots from B horizons were highly correlated with soil solution monomeric A1, and with A1 in 0.01 M SrC12 soil extracts. Stronger soil A1 extractants were generally poor predictors of concentrations of A1 in plant tissue. Sites with higher levels of plant-available A1 supported spruce trees with correspondingly lower foliar levels of Ca and Mg. As such, these field sites provided circumstantial evidence that AI may be interfering with Ca and Mg uptake and transport. No evidence was found of A1 interference with P uptake or transport at these sites.

AimsSuccessful establishment of species‐rich Nardus grasslands on ex‐agricultural land requires identification and removal of barriers to effective seed germination and seedling survival. Therefore, we investigate how germination and early development are affected by soil conditions from different restoration phases and how this relates to their specific plant strategies.LocationGrasslands and experiments in northern Belgium.MethodsWe selected three grassland restoration phases (Lolium perenne grasslands, grass–herb mix grasslands and species‐rich Nardus grasslands), which were characterized by a distinct plant community and soils with contrasting abiotic and biotic properties (respectively, eutrophic, mesotrophic and oligotrophic soils). In a first germination experiment we investigated the species‐specific responses (germination, lag time and emergence rate) of 70 grassland species (that typically occur along the restoration gradient) in each of the selected soils. Second, a mesoc...

Fine roots constitute a significant component of the net primary productivity (NPP) of forest ecosystems but are much less studied than aboveground NPP. Comparisons across sites and regions are also hampered by inconsistent methodologies, especially in tropical areas. Here, we present a novel dataset of fine root biomass, productivity, residence time, and allocation in tropical old‐growth rainforest sites worldwide, measured using consistent methods, and examine how these variables are related to consistently determined soil and climatic characteristics. Our pantropical dataset spans intensive monitoring plots in lowland (wet, semi‐deciduous, and deciduous) and montane tropical forests in South America, Africa, and Southeast Asia (n = 47). Large spatial variation in fine root dynamics was observed across montane and lowland forest types. In lowland forests, we found a strong positive linear relationship between fine root productivity and sand content, this relationship was even stro...

Bioindication of ecological variables such as humidity, temperature or pH by ecological indicator values of plants is a powerful tool for research in plant ecology, e.g. to detect early vegetation changes. Here, we provide a data set of ecological indicator values including niche width for an entire regional flora. We used an extensive database with floristic relevés from Southern France to recalibrate indicator values for light (L), temperature (T), continentality (K), air humidity (A), soil moisture (F), pH (R), productivity (N), soil texture (G), soil organic matter content (O) and salinity (S). Values were recalibrated using average values from co-occurring plants, enabling to develop indicator values for species not yet evaluated previously. Recalibrated values are on a continuous scale and we add standard deviation, median, first and third quartile for each indicator value. Linear regression of average indicator values against measured factors showed higher correlation with recalibrated values compared to original indicator values for temperature, pH and nitrogen, and comparable R 2 for moisture. Individual indicator systems performed better than a combination and applying different weighting procedures demonstrated the usefulness of inverse variance. We further illustrate graphically how recalibrated values and niche width increase ecological knowledge on plants.

Bioindication of ecological variables such as humidity, temperature or pH by ecological indicator values of plants is a powerful tool for research in plant ecology, e.g. to detect early vegetation changes. Here, we provide a data set of ecological indicator values including niche width for an entire regional flora. We used an extensive database with floristic relevés from Southern France to recalibrate indicator values for light (L), temperature (T), continentality (K), air humidity (A), soil moisture (F), pH (R), productivity (N), soil texture (G), soil organic matter content (O) and salinity (S). Values were recalibrated using average values from co-occurring plants, enabling to develop indicator values for species not yet evaluated previously. Recalibrated values are on a continuous scale and we add standard deviation, median, first and third quartile for each indicator value. Linear regression of average indicator values against measured factors showed higher correlation with recalibrated values compared to original indicator values for temperature, pH and nitrogen, and comparable R 2 for moisture. Individual indicator systems performed better than a combination and applying different weighting procedures demonstrated the usefulness of inverse variance. We further illustrate graphically how recalibrated values and niche width increase ecological knowledge on plants.

Context: Populus nigra L., is a species of cottonwood poplar that belongs to the Salicaceae family, is cultivated in multiple areas in Algeria, with an Algerian name of Safsaf. Aims: To evaluate the Populus nigra flower buds extract for its effects on brain modifications against aluminum-induced neurotoxicity in mice. The hypouricemic action of the extract was also evaluated. Methods: To evaluate the effect of extract on AlCl3-induced neurotoxicity on mice a battery of tests was performed to assess a spectrum of learning and memory functions. The hypouricemic action of the extract was studied by the measure of uric acid levels and liver xanthine oxidoreductase activity in normal and hyperuricemic mice. Results: Co-administration of P. nigra extract (200 mg/kg) and AlCl3 (100 mg/kg/day) combined with D-galactose (200 mg/kg/day) during four weeks was found to antagonize the harmful effects of AlCl3 by restoring all the test parameters. Moreover, extract restored the pyramidal cells to...

Background: Proton stress and aluminum (Al) toxicity are major constraints limiting crop growth and yields on acid soils (pH < 5). In Arabidopsis, STOP1 is a master transcription factor that controls the expression of a set of well-characterized Al tolerance genes and unknown processes involved in low pH resistance. As a result, loss-of-function stop1 mutants are extremely sensitive to low pH and Al stresses. Results: Here, we report on screens of an ethyl-methane sulphonate (EMS)-mutagenized stop1 population and isolation of nine strong stop1 suppressor mutants, i.e., the tolerant to proton stress (tps) mutants, with significantly enhanced root growth at low pH (4.3). Genetic analyses indicated these dominant and partial gain-of-function mutants are caused by mutations in single nuclear genes outside the STOP1 locus. Physiological characterization of the responses of these tps mutants to excess levels of Al and other metal ions further classified them into five groups. Three tps mutants also displayed enhanced resistance to Al stress, indicating that these tps mutations partially rescue the hypersensitive phenotypes of stop1 to both low pH stress and Al stress. The other six tps mutants showed enhanced resistance only to low pH stress but not to Al stress. We carried out further physiologic and mapping-by-sequencing analyses for two tps mutants with enhanced resistance to both low pH and Al stresses and identified the genomic regions and candidate loci in chromosomes 1 and 2 that harbor these two TPS genes. Conclusion: We have identified and characterized nine strong stop1 suppressor mutants. Candidate loci for two tps mutations that partially rescue the hypersensitive phenotypes of stop1 to low pH and Al stresses were identified by mapping-by-sequencing approaches. Further studies could provide insights into the structure and function of TPSs and the regulatory networks underlying the STOP1-mediated processes that lead to resistance to low pH and Al stresses in Arabidopsis.

Aluminum (Al) is a very common component of the earth&#39;s mineral composition. It is not essential element for life and is a constituent of rather inert minerals. Therefore, it has often been regarded as not presenting a significant health hazard. As a result, aluminum-containing agents been used in the preparation of many foodstuffs processing steps and also in elimination of particulate organic matter from water. More recently, the reduced pH of bodies of water resulting from acid rain has led to mobilization of aluminum-containing minerals into a more soluble form, and these have thus entered residential drinking water resources. By this means, the body burden of aluminum in humans has increased. Epidemiological and experimental findings indicate that aluminum is not as harmless as was previously thought, and that aluminum may contribute to the inception and advancement of Alzheimer&#39;s disease. Epidemiological data is reinforced by indications that aluminum exposure can resu...

State of the arts Currently, basic and applied research in dry acidic grasslands experiences a growing interest from vegetation science and nature conservation. However there is the problem that many valuable studies on acidic grasslands originate from nature conservation projects and are practically unknown because they have not been published in international journals. The present review contains a sizeable part of such material, particularly from Germany. Quite a few of these publications focus on vegetation composition and successional pathways (e.g.

Agricultural production in the Colombian Orinoco is affected by the high aluminum content found in 4.5 million hectares. Genotypes of different species have acquired different levels of tolerance and signaling pathways through various mechanisms, making a single model impossible. Some of the molecules commonly involved in the tolerance response have already been identified. To identify candidate genes to produce aluminum-tolerant cultivars, we consulted scientific articles published between 1987 and 2013. We obtained data of aluminum-tolerant materials and molecular mechanisms for tolerance through reports of techniques using hybridization, mutation, molecular marker-assisted selection and gene transfer. We found several reports on wholly or partially characterized genes with potential use in genetic engineering and in marker assisted selection to obtain aluminum tolerant genotypes.

Context: Populus nigra L., is a species of cottonwood poplar that belongs to the Salicaceae family, is cultivated in multiple areas in Algeria, with an Algerian name of Safsaf. Aims: To evaluate the Populus nigra flower buds extract for its effects on brain modifications against aluminum-induced neurotoxicity in mice. The hypouricemic action of the extract was also evaluated. Methods: To evaluate the effect of extract on AlCl3-induced neurotoxicity on mice a battery of tests was performed to assess a spectrum of learning and memory functions. The hypouricemic action of the extract was studied by the measure of uric acid levels and liver xanthine oxidoreductase activity in normal and hyperuricemic mice. Results: Co-administration of P. nigra extract (200 mg/kg) and AlCl3 (100 mg/kg/day) combined with D-galactose (200 mg/kg/day) during four weeks was found to antagonize the harmful effects of AlCl3 by restoring all the test parameters. Moreover, extract restored the pyramidal cells to...

Context: Populus nigra L., is a species of cottonwood poplar that belongs to the Salicaceae family, is cultivated in multiple areas in Algeria, with an Algerian name of Safsaf. Aims: To evaluate the Populus nigra flower buds extract for its effects on brain modifications against aluminum-induced neurotoxicity in mice. The hypouricemic action of the extract was also evaluated. Methods: To evaluate the effect of extract on AlCl3-induced neurotoxicity on mice a battery of tests was performed to assess a spectrum of learning and memory functions. The hypouricemic action of the extract was studied by the measure of uric acid levels and liver xanthine oxidoreductase activity in normal and hyperuricemic mice. Results: Co-administration of P. nigra extract (200 mg/kg) and AlCl3 (100 mg/kg/day) combined with D-galactose (200 mg/kg/day) during four weeks was found to antagonize the harmful effects of AlCl3 by restoring all the test parameters. Moreover, extract restored the pyramidal cells to near normal in cerebral cortex of mice. Extract, when administered three times orally to the normal and oxonate-induced hyperuricemic mice, was able to elicit significantly hypouricemic effect comparable to that of allopurinol. Conclusions: P. nigra flower buds extract can be considered as food enabling to antagonize AlCl3 toxicity and to control serum uric acid levels. Contexto: Populus nigra L. es una especie de álamo que pertenece a la familia Salicaceae, se cultiva en múltiples áreas en Argelia, con un nombre argelino de Safsaf. Resultados: La administración conjunta del extracto de P. nigra (200 mg/kg) y AlCl3 (100 mg/kg/día), combinado con D-galactosa (200 mg/kg día), durante cuatro semanas, antagonizó los efectos nocivos de AlCl3 al restaurar todos los parámetros de prueba. Además, el extracto restauró las células piramidales a casi normal en la corteza cerebral de ratones. El extracto, cuando se administró tres veces por vía oral a los ratones hiperuricémicos normales e inducidos por oxatos, fue capaz de provocar un efecto significativamente hipouricémico, comparable al del alopurinol. Conclusiones: El extracto de los brotes de flor de P. nigra puede considerarse como un alimento que permite antagonizar la toxicidad de AlCl3 y controlar los niveles séricos de ácido úrico.

Context: Populus nigra L., is a species of cottonwood poplar that belongs to the Salicaceae family, is cultivated in multiple areas in Algeria, with an Algerian name of Safsaf. Aims: To evaluate the Populus nigra flower buds extract for its effects on brain modifications against aluminum-induced neurotoxicity in mice. The hypouricemic action of the extract was also evaluated. Methods: To evaluate the effect of extract on AlCl3-induced neurotoxicity on mice a battery of tests was performed to assess a spectrum of learning and memory functions. The hypouricemic action of the extract was studied by the measure of uric acid levels and liver xanthine oxidoreductase activity in normal and hyperuricemic mice. Results: Co-administration of P. nigra extract (200 mg/kg) and AlCl3 (100 mg/kg/day) combined with D-galactose (200 mg/kg/day) during four weeks was found to antagonize the harmful effects of AlCl3 by restoring all the test parameters. Moreover, extract restored the pyramidal cells to...

World Agriculture faces daunting challenges in feeding the growing population today. Reduction in arable land extent due to numerous reasons threatens achievement of food and nutritional security. Under this back ground, agricultural use of acidic soils, which account for approximately 40 % of the world arable lands is of utmost important. However, due to aluminum (Al) toxicity and low available phosphorous (P) content, crop production in acidic soils is restricted. Citrus, in this context, gains worldwide recognition as a crop adapted to harsh environments. The present paper reviewed Al toxicity and possible toxicity alleviation tactics in citrus. As reported for many other crops, inhibition of root elongation, photosynthesis and growth is experienced in citrus also due to Al toxicity. Focusing at toxicity alleviation, interaction between boron (B) and Al as well as phosphorus and Al has been discussed intensively. Al toxicity in citrus could be alleviated by P through increasing immobilization of Al in roots and P level in shoots rather than through increasing organic acid secretion, which has been widely reported in other crops. Boron-induced changes in Al speciation and/or sub-cellular compartmentation has also been suggested in amelioration of root inhibition in citrus. Despite the species-dependent manner of response to Al toxicity, many commercially important citrus species can be grown successfully in acidic soils, provided toxicity alleviation Agro-biological tactics such as addition of phosphorous fertilizers are used properly.

Silicon is reported to reduce the toxic effects of Al on root elongation but the in planta mechanism by which this occurs remains unclear. Using seedlings of soybean (Glycine max) and sorghum (Sorghum bicolor), we examined the effect of up to 2 mM Si on root elongation rate (RER) in Al-toxic nutrient solutions. Synchrotron-based low energy X-ray fluorescence (LEXRF) was then used for the in situ examination of the distribution of Al and Si within cross-sections cut from the apical tissues of sorghum roots. The addition of Si potentially increased RER in Al-toxic solutions, with RER being up to ca. 0.3 mm h −1 (14%) higher for soybean and ca. 0.2 mm h −1 (17%) higher for sorghum relative to solutions without added Si. This improvement in RER could not be attributed to a change in Al-chemistry of the bulk nutrient solution, nor was it due to a change in the concentration of Al within the apical (0-10 mm) root tissues. Using LEXRF to examine sorghum, it was demonstrated that in roots exposed to both Al and Si, much of the Al was co-located with Si in the mucigel and outer apoplast. These observations suggest that Si reduces the toxicity of Al in planta through formation of Al-Si complexes in mucigel and outer cellular tissues, thereby decreasing the binding of Al to the cell wall where it is known to inhibit wall loosening as required for cell elongation.

In wheat (Triticum aestivum), it is commonly assumed that Al is detoxified by the release of organic anions into the rhizosphere, but it is also possible that detoxification occurs within the apoplast and symplast of the root itself. Using Al-resistant (ET8) and Al-sensitive (ES8) near-isogenic lines of wheat, we utilized traditional and synchrotron-based approaches to provide in situ analyses of the distribution and speciation of Al within root tissues. Some Al appeared to be complexed external to the root, in agreement with the common assumption. However, root apical tissues of ET8 accumulated four to six times more Al than ES8 when exposed to Al concentrations that reduce root elongation rate by 50% (3.5 μM Al for ES8 and 50 μM for ET8). Furthermore, in situ analyses of ET8 root tissues indicated the likely presence of Al-malate and other forms of Al, predominantly within the apoplast. To our knowledge, this is the first time that X-ray absorption near edge structure analyses hav...

The phytotoxic effects of aluminum (Al) on root systems of crop plants constitute a major agricultural problem in many areas of the world. Root exudation of Al-chelating molecules such as low-molecular-weight organic acids has been shown to be an important mechanism of plant Al tolerance/resistance. Differences observed in the physiology and electrophysiology of root function for two maize genotypes with contrasting Al tolerance revealed an association between rates of Al-activated root organic acid release and Al tolerance. Using these genotypes, we cloned ZmALMT1, a maize gene homologous to the wheat ALMT1 and Arabidopsis AtALMT1 genes that have recently been described as encoding functional, Al-activated transporters that play a role in tolerance by mediating Al-activated organic acid exudation in roots. The ZmALMT1 cDNA encodes a 451 amino acid protein containing six transmembrane helices. Transient expression of a ZmALMT1::GFP chimera confirmed that the protein is targeted to the plant cell plasma membrane. We addressed whether ZmALMT1 might underlie the Al-resistance response (i.e. Al-activated citrate exudation) observed in the roots of the Al-tolerant genotype. The physiological, gene expression and functional data from this study confirm that ZmALMT1 is a plasma membrane transporter that is capable of mediating elective anion efflux and influx. However, gene expression data as well as biophysical transport characteristics obtained from Xenopus oocytes expressing ZmALMT1 indicate that this transporter is implicated in the selective transport of anions involved in mineral nutrition and ion homeostasis processes, rather than mediating a specific Al-activated citrate exudation response at the rhizosphere of maize roots.

Th e Cerrado is the largest savanna of South America and its physiognomy varies from savanna to woodlands. Th ere are two main types of woodlands in the Cerrado: dystrophic woodlands, dominated by N-fi xing leguminous trees (LEG), and mesotrophic woodlands dominated by non-leguminous drought-tolerant trees (DRY), which are calcicoles and sensitive to Al 3+. Th e working hypothesis is that LEG and DRY are functional antagonists in terms of the acidifi cation/alkalization processes involving diff erent forms of inorganic nitrogen and pH, Ca 2+ and Al 3+ in soil. Tree species basal area and soil properties were used to investigate the antagonism between LEG and DRY using generalized linear models. Th e results suggest that LEG and DRY are antagonists. Th e LEG were positively associated with Al 3+ , NO 3and NH 4+ content and negatively related to increasing Ca 2+ content, whereas the DRY were negatively associated with Al 3+ , NO 3and NH 4+ and positively associated with increasing Ca 2+ content. Th e upper soil layer in plots dominated by LEG species became more acidic and the upper soil layer in plots dominated by DRY species became more alkaline. Th e results suggest that LEG and DRY are functional antagonists and their preferences for NH 4+ or NO 3might infl uence the way the Cerrado woodland changes.

Aluminum (Al) toxicity is one of the major limiting factors for crop production on acid soils that comprise significant portions of the world's lands. Al resistance in the cereal crop, Sorghum bicolor, is mainly achieved by Al-activated root apical citrate exudation, which is mediated by the plasma membrane localized citrate efflux transporter encoded by SbMATE. Here we precisely localize tissue-and cell-specific Al toxicity responses as well as SbMATE gene and protein expression in root tips of an Al-resistant near-isogenic-line (NIL). We found that Al induced the greatest cell damage and generation of reactive oxygen species specifically in the root distal-transition-zone (DTZ), a region 1-3 mm behind the root tip where transition from cell division to cell elongation occurs. These findings indicate that the root DTZ is the primary region of root Al stress. Furthermore, Al-induced SbMATE gene and protein expression were specifically localized to the epidermal and outer cortical cell layers of the DTZ in the Alresistant NIL, and the process was precisely coincident with the time course of Al induction of SbMATE expression and the onset of the recovery of roots from Al-induced damage. These findings show that SbMATE gene and protein expression are induced when and where the root cells experience the greatest Al stress. Hence, Al-resistant sorghum plants have evolved an effective strategy to precisely localize root citrate exudation to the specific site of greatest Al induced root damage, which minimizes plant carbon loss while maximizing protection of the root cells most susceptible to Al-damage.

Several recent studies have shown that citric acid/citrate (CA) can confer abiotic stress tolerance to plants. Exogenous CA application leads to improved growth and yield in crop plants under various abiotic stress conditions. Improved physiological outcomes are associated with higher photosynthetic rates, reduced reactive oxygen species, and better osmoregulation. Application of CA also induces antioxidant defense systems, promotes increased chlorophyll content, and affects secondary metabolism to limit plant growth restrictions under stress. In particular, CA has a major impact on relieving heavy metal stress by promoting precipitation, chelation, and sequestration of metal ions. This review summarizes the mechanisms that mediate CA-regulated changes in plants, primarily CA’s involvement in the control of physiological and molecular processes in plants under abiotic stress conditions. We also review genetic engineering strategies for CA-mediated abiotic stress tolerance. Finally, ...

Context: Populus nigra L., is a species of cottonwood poplar that belongs to the Salicaceae family, is cultivated in multiple areas in Algeria, with an Algerian name of Safsaf. Aims: To evaluate the Populus nigra flower buds extract for its effects on brain modifications against aluminum-induced neurotoxicity in mice. The hypouricemic action of the extract was also evaluated. Methods: To evaluate the effect of extract on AlCl3-induced neurotoxicity on mice a battery of tests was performed to assess a spectrum of learning and memory functions. The hypouricemic action of the extract was studied by the measure of uric acid levels and liver xanthine oxidoreductase activity in normal and hyperuricemic mice. Results: Co-administration of P. nigra extract (200 mg/kg) and AlCl3 (100 mg/kg/day) combined with D-galactose (200 mg/kg/day) during four weeks was found to antagonize the harmful effects of AlCl3 by restoring all the test parameters. Moreover, extract restored the pyramidal cells to...

In this work, the efficacy of two different strategies, used for 20 years (1992-2012) to restore a lignite mine dump, was investigated. The reclamation strategies were selection of the sterile materials, avoiding surface placement of pyritic materials, or surface application of topsoil material. Representative plots corresponding to each of both strategies were selected, as well as a control plot where reclamation techniques were not applied. An increase in total C, soluble Al, and exchangeable Al, as well as a decrease in pH, electrical conductivity, sulfate, and exchangeable cations concentrations took place during the study period. Avoiding pyritic materials on surface was the strategy giving the best acid-base conditions in the whole period, showing higher pH values (6.1-6.7) than application of topsoil (4.7-5.3), as well as the highest exchangeable Ca values (0.71-6.83 vs. 0.55-3.00 cmol (+) kg −1), and less exchange Al (0.22-2.80 vs. 0.99-3.72 cmol (+) kg −1) and soluble Al (0.04-0.60 vs. 0.19-37.47 mg L −1). Regarding fractionation of Al in soil solution, labile forms predominated throughout the study period, although organic forms (nonlabile Al and acid-soluble Al) showed an increase over time, which was in accordance with an increase in C concentration. The most toxic Al species (Al 3+ and Al-OH) were less abundant where pyritic materials were not placed on surface, compared with plots treated with topsoil (which did not differ from control plot for most parameters). The results of the study indicate that surface application of topsoil would not be justified as strategy to effectively restore lignite mine dump areas.

Os efeitos do alumínio (Al+3) sobre a morfologia e o acúmulo de compostos fenólicos foram avaliados em duas cultivares de sorgo (Sorghum bicolor (L.) Moench) com tolerância diferencial ao Al+3. As plantas foram mantidas em solução nutritiva durante dez dias, na presença (185 mM) ou na ausência de Al+3. Os ápices radiculares foram coloridos com hematoxilina férrica, sendo a intensidade da coloração observada na presença do Al+3 muito próxima entre as cultivares, o que inviabiliza a aplicação desse teste, isoladamente, para discriminação entre o genótipo sensível e o tolerante ao Al+3. As análises da morfologia externa e interna dos ápices radiculares de plantas tratadas com Al+3 também foram muito similares entre as duas cultivares, não permitindo a utilização dessas características para seleção entre a cultivar sensível e a tolerante. O maior acúmulo de lignina e, principalmente, a menor produção de compostos fenólicos, observados na presença do Al+3 nas raízes das plantas da cultiv...

Aluminum (Al) toxicity is a major worldwide agricultural problem. At low pH, Al speciates into the soluble and phyto-toxic form Al3+, inhibiting the root growth and affecting plant development. In Brazil, agriculture in acidic soils with elevated concentration of Al has significantly increased in the last decades. Therefore, in order to achieve efficient agriculture practices, the selection of plant cultivars with improved Al resistance has become crucial in this type of soils. In this work we have evaluated the Al resistance of six genotypes of grapevine rootstocks. The grapevine hardwood cuttings were grown in nutrient solution in the absence and presence of 250 and 500 μM Al at pH 4.2. The phenotypic indexes of relative root growth, fresh and dry root weight, root area, hematoxylin staining profile, and Al content were evaluated for all six genotypes. These phenotypic indexes allowed us to identify the &#39;Kober 5BB&#39;, &#39;Gravesac&#39;, &#39;Paulsen 1103&#39;, and &#39;IAC ...

Aims: Successful establishment of species-rich Nardus grasslands on ex-agricultural land requires identification and removal of barriers to effective seed germination and seedling survival. Therefore, we investigate how germination and early development are affected by soil conditions from different restoration phases and how this relates to their specific plant strategies. Location: Grasslands and experiments in northern Belgium. Methods: We selected three grassland restoration phases (Lolium perenne grasslands, grass-herb mix grasslands and species-rich Nardus grasslands), which were characterized by a distinct plant community and soils with contrasting abiotic and biotic properties (respectively, eutrophic, mesotrophic and oligotrophic soils). In a first germination experiment we investigated the species-specific responses (germination, lag time and emergence rate) of 70 grassland species (that typically occur along the restoration gradient) in each of the selected soils. Second, a mesocosm experiment was setup in which a mixture of 19 species (representative of the distinct grassland restoration phases) was grown together in the respective soils. Here, we analysed the intraspecific variation of plant growth, SLA and identified changes in community assembly. Results: Irrespective of soil influences, Nardus grassland species had significantly lower germination potentials and longer germination lag times than L. perenne grassland species. Germination (and its lag time) of grass-herb mix grassland species were negatively affected by the oligotrophic soils. Soil factors determined early growth patterns during the emergence and establishment phase. L. perenne grassland species exhibited a more plastic growth response and were highly dependent on soil type. Nardus grassland species exhibited large intraspecific variation in SLA, which was found to be significantly lower in the oligotrophic soils. Even though the difference in bio-available P between meso-trophic and oligotrophic soils was minor, Nardus grassland species were only able to compete in the oligotrophic soils (no significant difference in biomass between communities). Mesotrophic mesocosms exhibited the highest species richness after 200 d of growth. Conclusion: Plant species from the three grassland restoration phases display distinct germination strategies, irrespective of soil type. Interactions between growth strategies and soil factors determine competitive asymmetry and therefore shape community assembly in the distinct grassland phases.

Aluminum (Al) toxicity is one of the major limiting factors for crop production on acid soils that comprise significant portions of the world's lands. Al resistance in the cereal crop, Sorghum bicolor, is mainly achieved by Al-activated root apical citrate exudation, which is mediated by the plasma membrane localized citrate efflux transporter encoded by SbMATE. Here we precisely localize tissue-and cell-specific Al toxicity responses as well as SbMATE gene and protein expression in root tips of an Al-resistant near-isogenic-line (NIL). We found that Al induced the greatest cell damage and generation of reactive oxygen species specifically in the root distal-transition-zone (DTZ), a region 1-3 mm behind the root tip where transition from cell division to cell elongation occurs. These findings indicate that the root DTZ is the primary region of root Al stress. Furthermore, Al-induced SbMATE gene and protein expression were specifically localized to the epidermal and outer cortical cell layers of the DTZ in the Alresistant NIL, and the process was precisely coincident with the time course of Al induction of SbMATE expression and the onset of the recovery of roots from Al-induced damage. These findings show that SbMATE gene and protein expression are induced when and where the root cells experience the greatest Al stress. Hence, Al-resistant sorghum plants have evolved an effective strategy to precisely localize root citrate exudation to the specific site of greatest Al induced root damage, which minimizes plant carbon loss while maximizing protection of the root cells most susceptible to Al-damage.

Aluminum (Al) is the most abundant metal in the earth&#39;s crust and is found naturally in the air, water, and soil. Al may pose a major threat to humans, causing diseases and bone disorders. Nevertheless, the effects of Al on alveolar bone are not reported in the literature. Here, we investigated the effects of sub-chronic intoxication with Al citrate in a model of alveolar bone loss, induced by ligature, in male Wistar rats. The animals were exposed to Al citrate (100 mg/kg/day), by gavage, for 30 days. We used 40 rats equally divided into four groups: Control; Experimental Periodontitis (EPeriodontitis); Al; Al+EPeriodontitis. After exposure period, we evaluated the concentration of Al in the blood and alveolar bone, as well as the Al measurement in alveolar bone. The results showed that the Al exposure promoted distribution of Al in blood serum and in the alveolar bone. The Al exposure per si results in alveolar bone loss as well as potentiates damages of periodontitis induced ...

Several aluminium toxicity indices were applied to acid soils developed from various parent materials (granodiorite, slate and limestone) and sustaining various tree species (Quercus robur, Pinus radiata and Eucalyptus nitens), in Galicia, NW Spain. Some indices are based on the composition of the soil solid or liquid phases and some on the composition of the leaf or root tissues. The base cation saturation of the exchange complex was used as an index based on the composition of the soil solid phase. The indices based on the soil solution composition were various cation species concentrations, including phytotoxic aluminium species, or concentration ratios. The concentrations of Al and Ca and the Ca/Al molar ratio were used as indices based on the leaf and root tissue compositions. The application of various indices led to different results. According to indices based on the soil solution or plant tissue compositions, the greatest problems are expected in soils developed from limestone or granodiorite and sustaining P. radiata; fewer problems are expected in soils developed from slate and sustaining Q. robur. On the contrary, the saturation of the exchange complex predicts the highest aluminium toxicity risk in soils developed from slate and sustaining Q. robur, and the lowest risk in soils sustaining E. nitens.

The paper discusses the question whether geographical information systems (GIS) and digital elevation models (DEM) are useful tools for studying correlations between topographic attributes of a given area, and vascular flora requirements reflected by ecological indicator values (EIVs). The model object was a 4-km-long gorge section of the Sopot river valley (80.5 ha), the Central Roztocze Highlands, South-East Poland. Species lists for 40 ca. 200-m-long and 100-350-m-wide sections, according to the river course, separately for the left and right riverbanks, were made. The analysis of the area was based on a 3-meter resolution DEM. We applied primary topographic attributes: slope, and planar, vertical, and total curvatures and also secondary topographic attributes: solar radiation (SRAD) and topographic wetness index (TWI), as well as other terrain characters: denivelation, total, flat and upslope area of each section. Using the multivariate analyses, we analysed relationships betwee...

Context: Populus nigra L., is a species of cottonwood poplar that belongs to the Salicaceae family, is cultivated in multiple areas in Algeria, with an Algerian name of Safsaf. Aims: To evaluate the Populus nigra flower buds extract for its effects on brain modifications against aluminum-induced neurotoxicity in mice. The hypouricemic action of the extract was also evaluated. Methods: To evaluate the effect of extract on AlCl3-induced neurotoxicity on mice a battery of tests was performed to assess a spectrum of learning and memory functions. The hypouricemic action of the extract was studied by the measure of uric acid levels and liver xanthine oxidoreductase activity in normal and hyperuricemic mice. Results: Co-administration of P. nigra extract (200 mg/kg) and AlCl3 (100 mg/kg/day) combined with D-galactose (200 mg/kg/day) during four weeks was found to antagonize the harmful effects of AlCl3 by restoring all the test parameters. Moreover, extract restored the pyramidal cells to...

Aluminium smelters are major sources of F emission to the environment. We studied, in laboratory experiments, the sorption and desorption of fluoride on organic and mineral horizons of soils located within 2 km from one of these factories, situated in the northern coast of Galicia (NW Spain). The soils, developed from granite, are acid (pH H 2 O 3.9-5.5), rich in organic matter (4-16 % C in the A horizon) and most A horizons have high Al saturation in the exchange complex. All samples showed a notable F sorption, between 1,066 and 1,589 mg kg-1 , after adding 200 mg F L-1 , which accounts for 53-80 % of F added. The sorption was slightly higher in the A horizons than in the respective organic horizons (differences of up to 194 mg kg-1). The fluoride sorption upon addition of 200 mg F L-1 correlated significantly (p \ 0.05) with soil pH in water (r =-0.77), iron extracted by acid ammonium oxalate (r = 0.68), aluminium plus iron extracted by acid ammonium oxalate (r = 0.63), exchange aluminium (r = 0.52) and clay percentage in soil (r = 0.76). The F sorption fitted to both Langmuir and Freundlich models. Desorbed F accounted for only 12-22 % of sorbed fluoride and correlated (p \ 0.05) negatively with non-crystalline (extracted by acid ammonium oxalate) Fe (r =-0.51) and clay content (r =-0.74) and positively with organic matter (r = 0.69) and with the effective cation exchange capacity of the soil (r = 0.50).

Several aluminium toxicity indices were applied to acid soils developed from various parent materials (granodiorite, slate and limestone) and sustaining various tree species (Quercus robur, Pinus radiata and Eucalyptus nitens), in Galicia, NW Spain. Some indices are based on the composition of the soil solid or liquid phases and some on the composition of the leaf or root tissues. The base cation saturation of the exchange complex was used as an index based on the composition of the soil solid phase. The indices based on the soil solution composition were various cation species concentrations, including phytotoxic aluminium species, or concentration ratios. The concentrations of Al and Ca and the Ca/Al molar ratio were used as indices based on the leaf and root tissue compositions. The application of various indices led to different results. According to indices based on the soil solution or plant tissue compositions, the greatest problems are expected in soils developed from limestone or granodiorite and sustaining P. radiata; fewer problems are expected in soils developed from slate and sustaining Q. robur. On the contrary, the saturation of the exchange complex predicts the highest aluminium toxicity risk in soils developed from slate and sustaining Q. robur, and the lowest risk in soils sustaining E. nitens.

Aluminium smelters are major sources of F emission to the environment. We studied, in laboratory experiments, the sorption and desorption of fluoride on organic and mineral horizons of soils located within 2 km from one of these factories, situated in the northern coast of Galicia (NW Spain). The soils, developed from granite, are acid (pH H 2 O 3.9-5.5), rich in organic matter (4-16 % C in the A horizon) and most A horizons have high Al saturation in the exchange complex. All samples showed a notable F sorption, between 1,066 and 1,589 mg kg-1 , after adding 200 mg F L-1 , which accounts for 53-80 % of F added. The sorption was slightly higher in the A horizons than in the respective organic horizons (differences of up to 194 mg kg-1). The fluoride sorption upon addition of 200 mg F L-1 correlated significantly (p \ 0.05) with soil pH in water (r =-0.77), iron extracted by acid ammonium oxalate (r = 0.68), aluminium plus iron extracted by acid ammonium oxalate (r = 0.63), exchange aluminium (r = 0.52) and clay percentage in soil (r = 0.76). The F sorption fitted to both Langmuir and Freundlich models. Desorbed F accounted for only 12-22 % of sorbed fluoride and correlated (p \ 0.05) negatively with non-crystalline (extracted by acid ammonium oxalate) Fe (r =-0.51) and clay content (r =-0.74) and positively with organic matter (r = 0.69) and with the effective cation exchange capacity of the soil (r = 0.50).

Several recent studies have shown that citric acid/citrate (CA) can confer abiotic stress tolerance to plants. Exogenous CA application leads to improved growth and yield in crop plants under various abiotic stress conditions. Improved physiological outcomes are associated with higher photosynthetic rates, reduced reactive oxygen species, and better osmoregulation. Application of CA also induces antioxidant defense systems, promotes increased chlorophyll content, and affects secondary metabolism to limit plant growth restrictions under stress. In particular, CA has a major impact on relieving heavy metal stress by promoting precipitation, chelation, and sequestration of metal ions. This review summarizes the mechanisms that mediate CA-regulated changes in plants, primarily CA’s involvement in the control of physiological and molecular processes in plants under abiotic stress conditions. We also review genetic engineering strategies for CA-mediated abiotic stress tolerance. Finally, ...

Background A major limiting factor for plant growth is the aluminum (Al) toxicity in acidic soils, especially in tropical regions. The exclusion of Al from the root apex through root exudation of organic acids such as malate and citrate is one of the most ubiquitous tolerance mechanisms in the plant kingdom. Two families of anion channels that confer Al tolerance are well described in the literature, ALMT and MATE family. Results In this study, sugarcane plants constitutively overexpressing the Sorghum bicolor MATE gene (SbMATE) showed improved tolerance to Al when compared to non-transgenic (NT) plants, characterized by sustained root growth and exclusion of aluminum from the root apex based on the result obtained with hematoxylin staining. In addition, genome-wide analysis of the recently released sugarcane genome identified 11 ALMT genes and molecular studies showed potential new targets for aluminum tolerance. Conclusions Our results indicate that the transgenic plants overexpre...

Aluminum (Al) toxicity is one of the major limiting factors for crop production on acid soils that comprise significant portions of the world's lands. Al resistance in the cereal crop, Sorghum bicolor, is mainly achieved by Al-activated root apical citrate exudation, which is mediated by the plasma membrane localized citrate efflux transporter encoded by SbMATE. Here we precisely localize tissue-and cell-specific Al toxicity responses as well as SbMATE gene and protein expression in root tips of an Al-resistant near-isogenic-line (NIL). We found that Al induced the greatest cell damage and generation of reactive oxygen species specifically in the root distal-transition-zone (DTZ), a region 1-3 mm behind the root tip where transition from cell division to cell elongation occurs. These findings indicate that the root DTZ is the primary region of root Al stress. Furthermore, Al-induced SbMATE gene and protein expression were specifically localized to the epidermal and outer cortical cell layers of the DTZ in the Alresistant NIL, and the process was precisely coincident with the time course of Al induction of SbMATE expression and the onset of the recovery of roots from Al-induced damage. These findings show that SbMATE gene and protein expression are induced when and where the root cells experience the greatest Al stress. Hence, Al-resistant sorghum plants have evolved an effective strategy to precisely localize root citrate exudation to the specific site of greatest Al induced root damage, which minimizes plant carbon loss while maximizing protection of the root cells most susceptible to Al-damage.