Interactive effects of selenium and arsenic on their uptake by Pteris vittata L. under hydroponic conditions

The interactive effects of selenium (Se) and arsenic (As) on plant uptake of Se and As have rarely been documented. In this study, the interactive effects of As and Se on their uptake by Chinese brake fern (Pteris vittata), an As-hyperaccumulator and Se-accumulator, were explored in two hydroponic experiments based on a two-factor, five-level central composite design. At Se levels of less than 2.5 mg L^?1, increasing amounts of As stimulated the uptake of Se in Chinese brake fern roots, possibly because of the beneficial effects of Se. In contrast, at Se concentrations greater than 2.5 mg L^?1, As suppressed the uptake of Se in Chinese brake fern roots. Uptake of As by both fronds and roots of Chinese brake fern was suppressed by the addition of Se, indicating the antagonistic effects of Se on As. In addition, at Se concentrations of less than 2.5 mg L^?1, As stimulated the translocation of Se from roots to fronds; meanwhile, the addition of Se resulted in reduced translocation of As from roots to fronds. These findings demonstrate the interactive effects of As and Se on their uptake by Chinese brake fern.     

Effects of Se on the uptake of essential elements in Pteris vittata L.

Selenium has been proven to be an antioxidant in plants at low dosages. To understand better the mechanisms of Se toxicity and benefit to plants, more investigations about effects of Se on the uptake of essential elements in plants would be desirable. In this study, hydroponic (nutrient solution culture) and pot (soil culture) experiments were simultaneously conducted to investigate the effects of Se on the uptake and distribution of essential elements in Pteris vittata. L (Chinese brake fern), an arsenic (As)-hyperaccumulator and a selenium (Se)-accumulator. Chinese brake fern took up much more Se in nutrient solution culture than in soil culture, with the highest Se content recorded as 1,573 mg kg^?1 in the roots, demonstrating remarkable tolerance to Se. In soil culture, Chinese brake fern also accumulated high content of Se, with the highest content measured as 81 mg kg^?1 and 233 mg kg^?1, in the fronds and roots, respectively. In soil culture, the addition of Se suppressed the uptake of most measured elements, including magnesium (Mg), potassium (K), phosphorus (P), iron (Fe), copper (Cu) and zinc (Zn). In nutrient solution culture, when the Se content in the tissues of Chinese brake fern was relatively low, the supplementation of Se suppressed the uptake of most essential elements; however, with the increase of Se content, stimulation effects of Se on the uptake of Ca, Mg, K were observed. An initial decrease followed by a rapid increase of Fe content in the fronds of Chinese brake fern was found with Se addition and tissue Se content increasing in nutrient solution culture, suggesting antagonistic and synergic roles of Se on these elements under low and high Se exposure, respectively. We suggest that Ca, Mg, K may be involved in the tolerance mechanism of Se, and that the regulation of Fe accumulation by Se in the fronds might be partially due to the dual effects of Se on Chinese brake fern.     

Interaction of arsenic and phosphate on their uptake and accumulation in Chinese brake fern

Interactive effects of arsenate (As (V)) and phosphate (Pi) were investigated under hydroponic culture. Arsenic concentrations in fronds and roots of Chinese brake fern (Pteris vittata L.) significantly (p < 0.05) increased with increasing As (V), but decreased (p < 0.05) with increasing Pi in nutrient solution. Phosphate uptake was significantly (p < 0.05) inhibited by 1000 micromol L(-1) As (V). Under 100 micromol L(-1) As (V), frond phosphorus (P) increased at 100 and 1000 micromol L(-1) Pi, and root P increased at 250 micromol L(-1) Pi exposures. Arsenic and P concentrations in fronds and roots of Chinese brake fern were negatively correlated (p < 0.05). Arsenate treatments enhanced As and P transport to fronds, while increasing Pi inhibited their transportation, with highest frond P and As (%) obtained under 100 micromol L(-1) treatment. pH values in nutrient solution increased with increasing exposure time, but decreased with increasing Pi levels. Dissolved organic carbon (DOC) contents (dry weight) in nutrient solution decreased with increasing Pi levels, both for treatments with and without As (V). Arsenate at 1000 micromol L(-1) significantly (p < 0.05) increased DOC contents, especially for treatment without Pi. Six organic acids were detected in root exudates of Chinese brake fern, with oxalic and malic acids being most dominant.     

Root exudates and arsenic accumulation in arsenic hyperaccumulating Pteris vittata and non-hyperaccumulating Nephrolepis exaltata

This study compared the roles of root exudates collected from two fern species, the As hyperaccumulating Chinese Brake fern (Pteris vittata L.) and the As-sensitive Boston fern (Nephrolepis exaltata L.), on As-mobilization of two As minerals (aluminum arsenate and iron arsenate) and a CCA (chromated copper arsenate)-contaminated soil as well as plant As accumulation. Chinese Brake fern exuded 2 times more dissolved organic carbon (DOC) than Boston fern and the difference was more pronounced under As stress. The composition of organic acids in the root exudates for both ferns consisted mainly of phytic acid and oxalic acid. However, Chinese Brake fern produced 0.46 to 1.06 times more phytic acid than Boston fern under As stress, and exuded 3–5 times more oxalic acid than Boston fern in all treatments. Consequently, root exudates from Chinese Brake fern mobilized more As from aluminum arsenate (3–4 times), iron arsenate (4–6 times) and CCA-contaminated soil (6–18 times) than Boston fern. Chinese Brake fern took up more As and translocated more As to the fronds than Boston fern. The molar ratio of P/As in the roots of Chinese Brake fern was greater than in the fronds whereas the reverse was observed in Boston fern. These results suggested that As-mobilization from the soil by the root exudates (enhancing plant uptake), coupled with efficient As translocation to the fronds (keeping a high molar ratio of P/As in the roots), are both important for As hyperaccumulation by Chinese Brake fern.     

Antioxidant responses of hyper-accumulator and sensitive fern species to arsenic

Plant species capable of hyper-accumulating heavy metals are of considerable interest for phytoremediation, and differ in their ability to accumulate metals from the environment. This work aims to examine (i) arsenic accumulation in three fern species [Chinese brake fern (Pteris vittata L.), slender brake fern (Pteris ensiformis Burm. f.), and Boston fern (Nephrolepis exaltata L.)], which were exposed to 0, 150, or 300 muM of arsenic (Na(2)HAsO(4).7H(2)O), and (ii) the role of anti-oxidative metabolism in arsenic tolerance in these fern species. Arsenic accumulation increased with an increase in arsenic concentration in the growth medium, the most being found in P. vittata fronds showing no toxicity symptoms. In addition, accumulation was highest in the fronds, followed by the rhizome, and finally the roots, in all three fern species. Thiobarbituric acid-reacting substances, indicators of stress in plants, were found to be lowest in P. vittata, which corresponds with its observed tolerance to arsenic. All three ferns responded differentially to arsenic exposure in terms of anti-oxidative defence. Higher levels of superoxide dismutase, catalase, and ascorbate peroxidase were observed in P. vittata than in P. ensiformis and N. exaltata, showing their active involvement in the arsenic detoxification mechanism. However, no significant increase was observed in either guaiacol peroxides or glutathione reductase in arsenic-treated P. vittata. Higher activity of anti-oxidative enzymes and lower thiobarbituric acid-reacting substances in arsenic-treated P. vittata correspond with its arsenic hyper-accumulation and no symptoms of toxicity.     

Study on air pollution in Beijing’s major industrial areas using multielements in biomonitors and NAA techniques

Three kinds of plant leaves, Chinese white aspen, arborvitae, and pine needles, have been sampled from the Yanshan Oil refinery complex, the Capital Iron and Steel Factory, and Badachu, a control area in Beijing, as biomonitors for air-pollution studies. Each sample was divided into two parts, washed, and unwashed. Thirty-one trace elements (As, Au, Br, Ca, Cd, K, La, Lu, Mo, Na, Sb, Sm, U, W, Yb, Ba, Ce, Co, Cr, Cs, Eu, Fe, Hf, Hg, Rb, Sc, Se, Sr, Ta, Tb, Th, and Zn) have been determined by using the relative and the K₀ methods of instrumental neutron activation analysis (NAA) techniques. The results indicated the following: (1) The concentration of trace elements in unwashed samples are much higher than these in washed samples; (2) the area around Capital Iron and Steel Factory is heavily polluted, and the Yanshan Oil refinery complex area is moderately polluted; (3) Chinese white aspen is a good biomonitor in particular seasons and pine needles are better than arborvitae for yearly monitoring; (4) elements As, Cd, Hg, Co, Rb, Sb, W, and Zn are highly absorbed by Chinese white aspen. Pine needles are sensitive for the absorption the elements Br, Cr, Cd, Fe, Sc, Cs and rare earth elements, but arborvitae is very sensitive for the absorption of Sr.     

Characterization of arsenate reductase in the extract of roots and fronds of Chinese brake fern, an arsenic hyperaccumulator

Root extracts from the arsenic (As) hyperaccumulating Chinese brake fern (Pteris vittata) were shown to be able to reduce arsenate to arsenite. An arsenate reductase (AR) in the fern showed a reaction mechanism similar to the previously reported Acr2p, an AR from yeast (Saccharomyces cerevisiae), using glutathione as the electron donor. Substrate specificity as well as sensitivity toward inhibitors for the fern AR (phosphate as a competitive inhibitor, arsenite as a noncompetitive inhibitor) was also similar to Acr2p. Kinetic analysis showed that the fern AR had a Michaelis constant value of 2.33 mM for arsenate, 15-fold lower than the purified Acr2p. The AR-specific activity of the fern roots treated with 2 mM arsenate for 9 d was at least 7 times higher than those of roots and shoots of plant species that are known not to tolerate arsenate. A T-DNA knockout mutant of Arabidopsis (Arabidopsis thaliana) with disruption in the putative Acr2 gene had no AR activity. We could not detect AR activity in shoots of the fern. These results indicate that (1) arsenite, the previously reported main storage form of As in the fern fronds, may come mainly from the reduction of arsenate in roots; and (2) AR plays an important role in the detoxification of As in the As hyperaccumulating fern.     

An environmental research on trace elements in freshwater fish by neutron activation analysis

For a case study of environmental contamination, radiochemical activation analysis has been applied to the crucians collected in the Han River. Sixteen trace elements (Hg, Cd, As, Br, Cu, Na, K, Se, Cr, Hf, Rb, Fe, Zn, Co, La, and Cs) were separated into three groups using distillation and diethyldithiocarbamate extraction methods, and their contents were determined by a single comparator method. Compared with the values 15 years ago, the values for mercury and cadmium have been drastically decreased at the middle and lower part of the river, but no typical change is found in other elements.     

Determination of trace elements in aerosol samples by Instrumental Neutron Activation Analysis

Two nuclear techniques, Energy-Dispersive X-Ray Fluorescence Analysis (EDXRF) and Instrumental Neutron Activation Analysis (INAA), were used to analyze aerosol samples collected in the city of São Paulo, Brazil. Na, Cl, Mn, V, Al, Sm, Mo, W, La, As, Br, Sb, K, Ba, Se, Th, Cr, Rb, Ca, Fe, Ce, and Sc were determined by INAA, and Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Hg, and Pb were determined by EDXRF. A preliminary identification of the main source of the atmospheric aerosol was performed based on enrichment factor and correlation coefficient calculations.

     

A survey of trace elements in fresh-water fish and rice along the Han River by neutron activation analysis

For a case study of environmental pollution, radiochemical neutron activation analysis (RNAA) was applied to the crucian and rice collected along the Han River. The crucian was analyzed for three times in 1973, 1987, and 1990. Sixteen trace elements (Hg, Cd, As, Br, Cu, Na, K, Se, Cr, Hf, Rb, Fe, Zn, Co, La, and Cs) were determined by RNAA using distillation and diethyldithiocarbamate extraction methods. Contents of Na, K, Se, Hf, Fe, Zn, and Co were almost constant regardless of the sampling place and year. The contents of the other elements showed increasing trends down river, especially in the first investigation. At the lower part of the river, the contents showed decreasing trends with the time of sampling, especially during the first two investigations. These trends were typical for Hg and Cd. Rice was analyzed by the same method for 12 elements, and the results showed no regional trends, but have decreased after 1973.     

Multielement compositions of marine phytoplankton samples from coastal areas of japan by instrumental neutron activation analysis

Phytoplankton samples were collected during spring bloom of diatoms from three coastal areas of Japan using a NORPAC P-25 net (25-Μm opening) with a NGG52 prenet (335-Μm opening), and 25 major and trace elements have been analyzed by INAA. Concentration ranges of analyzed phytoplankton samples are much wider than the concentration ranges compiled by Bowen (1979) except for As, and data of marine phytoplankton samples for Br, Sb, Hf, Sc, La, Ce, Sm, and Eu were not included in the compilation. The 25 analyzed elements have been categorized into three groups: elements showing positive correlation with Br, positive correlation with Al, and no positive correlation with Br or Al. The marine phytoplankton samples have been plotted on a Masuzawa-Koyama-Terazaki (MKT) plot and it proved that the MKT plot is applicable to marine phytoplankton samples.     

Phytoremediation of an arsenic-contaminated site using Pteris vittata L.: a two-year study

A field study was conducted to determine the efficiency of Chinese brake fern (Pteris vittata L.), an arsenic hyperaccumulator, on removal of arsenic from soil at an arsenic-contaminated site. Chinese brake ferns were planted on a site previously used to treat wood with chromated copper arsenate (CCA). Arsenic concentrations in surface and profile soil samples were determined for 2000, 2001, and 2002. In both 2001 and 2002, senesced and senescing fronds only, as well as all fronds, were harvested. Frond arsenic concentrations were not significantly different between the three harvests. Compared to senesced fronds, live fronds resulted in the greatest amount of arsenic removal. There were no significant differences in soil arsenic concentrations between 2000, 2001, and 2002, primarily due to the extreme variability in soil arsenic concentrations. However, the mean surface soil arsenic was reduced from 190 to 140 mg kg(-1). Approximately 19.3 g of arsenic were removed from the soil by Chinese brake fern. Therefore, this fern is capable of accumulating arsenic from the CCA -contaminated site and may be competitive, in terms of cost, to conventional remediation systems. However, better agronomic practices are needed to enhance plant growth and arsenic uptake to obtain maximum soil arsenic removal and to minimize remediation time.     

Trace elements in human parotid saliva

Although various proteins and some electrolytes have been measured in human saliva, little systematic data about the major and minor elemental components of this body fluid have been obtained. In order to obtain such data, concentrations of C, Na, P, Cl, K, Ca, Sc, Cr, Fe, Co, Zn, Se, Br, Rb, Sb, I, and Cs in human parotid saliva were measured by instrumental nuclear methods. The data obtained confirmed the relative lack of Zn in saliva of patients with hypogeusia (decreased taste acuity) and suggested that concentrations of Na, Cl, Br, and Ca followed the order: normals > hypogeusia > hyposmia (decreased smell acuity). To compare concentrations of elements in saliva with those in blood and urine, absolute concentrations were normalized to that of Na through the use of a concept called an enrichment factor. On this basis, parotid saliva is relatively depleted in Se, Zn, and Fe and enriched for most other elements relative to blood plasma indicating that the fluid is not simply a transudate of blood plasma. Using this same technique, saliva composition was found more similar to urine than blood plasma, being relatively depleted in Se, Cs, and Co, being enriched in I, Br, and Cr and having about the same relative concentrations of P, Cl, Zn, Fe, Ca, K, and Rb. As the total body concentrations of many of the enriched elements in saliva are extremely small, their enrichment in saliva suggests special roles for these elements in the oral cavity. Because of its accessibility, ease of collection, and interaction with some body constituents, saliva represents a useful, albeit neglected, tool in the diagnosis of some physiological and pathological changes in body function and in understanding important aspects of trace metal metabolism.     

Uptake and distribution of selenium in different fern species

There has been an interest in using hyperaccumulating plants for the removal of heavy metals and metalloids. High selenium (Se) concentrations in the environment are detrimental to animals, humans, and sustainable agriculture, yet selenium is also an essential nutrient for humans. This experiment was conducted to screen fern plants for their potential to accumulate selenium. Eleven fern species, Pteris vittata, P. quadriaurita, P. dentata, P. ensiformis, P. cretica, Dryopteris erythrosora, Didymochlaena truncatula, Adiantum hispidulum, Actiniopteris radiata, Davallia griffithiana, and Cyrtomium fulcatum, were grown under hydroponic conditions for one week at 20 mg L(-1) selenate or selenite. Root Se concentrations reached 245-731 and 516-1082 mg kg(-1) when treated with selenate and selenite, respectively. The corresponding numbers in the fronds were 153-745 and 74-1,028 mg kg(-1) with no visible toxicity symptoms. Only three fern species were able to accumulate more Se in the fronds than the roots, which were D. griffithiana when treated with selenate, P. vittata when treated with selenite, and A. radiata regardless of the forms of Se. A. radiata was the best species overall for Se accumulation. More research is needed to further determine the potential of the fern species identified in this study for phytoremediation of the Se contaminated soils and water.     

An elemental correlation study in cancerous and normal breast tissue with successive clinical stages by neutron activation analysis

Influence of trace elements in body metabolism and their physiological importance in various diseases have motivated their accurate and quantitative determination in biological tissues and fluids. Instrumental Neutron Activation Analysis (INAA) using short and long term irradiation has been employed to determine five minor elements (Cl, K, Na, Mg, P) and 15 trace elements (As, Br, Co, Cr, Cs, Cu, Fe, Hg, Mn, Rb, Sb, Se, Sc, Sr, and Zn) in cancerous and normal breast tissue from 30 patients of four clinical stages. Several elements show enhancement in cancerous breast tissue. Selenium shows maximum enhancement of 94.7% followed by K (81.6%), Sc (66.7%), Cu (58.2%), Na (48.5%), P (44.4%), and Zn (39.2%). Some element, such as Fe, Cr, and Mn, are depressed by 30.8, 30.1, and 12.8%, respectively. These elements compete for binding sites in the cell, change its enzymatic activity and exert direct or indirect action on the carcinogenic process accelerating the growth of tumors. This is further evidenced by histopathological examination of cancerous cells showing poor cytological differentiation. An attempt has been made to correlate trace element concentrations of Se, Cu, Zn, Rb, Br, Hg, As, Co, Fe, Cr, and Mn and the ratios of Se/Zn, K/P, Cu/Zn, Na/K, and Se/Fe with the clinical stages of cancer. Inhibition of enzymatic activity caused by variation in trace element concentrations results in immunological breakdown of the body system.     

Phytoextraction: simulating uptake and translocation of arsenic in a soil-plant system

The uptake, transport, and accumulation of metals by plants are functions central to successful phytoextraction. This study investigates the uptake and translocation of arsenic from a contaminated sandy soil by a mature Chinese brake fern (Pteris vittata L.). An existing mathematical model for the coupled transport of water, heat, and solutes in the soil-plant-atmosphere continuum (CTSPAC) was modified to examine the flow of water as well as the uptake and translocation of total arsenic in the xylem of the fern. This model was calibrated using greenhouse measurements before its application. Simulation results showed that about 20% of the soil arsenic was removed by the fern in 10 d, of which about 90% of the arsenic was stored in the fronds and 10% in the roots. Although arsenic mass in the plant tissues increased consecutively with time, arsenic concentration in the xylem sap of the root tips has a typical diurnal distribution pattern: increasing during the day and decreasing at night, resulting from daily variations of frond surface water transpiration. The largest difference in simulated arsenic concentration in the root tips between the day and night was about 5%. This study also suggests that the use of transpiration stream concentration factor (TSCF), which is defined as the ratio of chemical concentration in the xylem sap to that in the external solution, to evaluate the translocation efficiency of arsenic for the hyperaccumulator Chinese brake fern (Pteris vittata L.) could be limited.     

Trace element correlations in the blood of indian women with breast cancer

Fourteen minor (Na, K, P, Fe) and trace (Br, Co, Cr, Cs, Hg, Rb, Sb, Se, Sr, Zn) elements have been determined in pre and postoperative blood samples of 10 breast-cancer-affected. Indian women and compared with controls. The study showed elevation of Cr, Hg, Fe, Rb, Sb, and Zn and lowering of Se, K, P, and Sr contents in the blood of cancer patients. Most elemental contents in pre and postoperative stages remain unaltered except Br, Co, and Sb. Statistical significance of Fe, Se, Zn, and Hg levels has been tested by box plots. Lowering of Se in blood (-54.4%) is correlated with its enhancement in cancerous breast tissue (94.7%) of various clinical stages. Se/Zn and Se/Fe ratios are lowered in the blood of cancer patients, whereas Na/K ratio is only marginally enhanced. An attempt has been made to correlate Se levels with the dietary intake and breast cancer risk vis-a-vis American and Japanese women.     

Root distributions and elemental accumulations of Chinese brake (Pteris vittata L.) from As-contaminated soils

A field investigation was conducted to understand the root distributions and elemental accumulations of Chinese brake (Pteris vittata L.), an As-hyperaccumulator, grown in soils with a gradient of As concentration near an arsenic sulphide mine. The root distribution was affected not only by the levels of soil As, but also by soil texture. Plants grew better in sandy loam soils than in clay soils. Increases in the ratio of frond biomass to underground biomass were correlated with decreasing soil As concentration. Root densities of the plant decreased from 0–10 cm, 10–20 cm to 20–30 cm in the soil profiles. Most of the roots were concentrated in the upper 0–10 cm layer. Under high As conditions, As concentrations in different tissues followed the trends: pinnae > rhizomes ≈ roots of 0–10 cm > roots of 10–20 cm > roots of 20–30 cm > petioles, however, As concentrations in pinnae were higher than those in rhizomes under low As conditions. The rhizomes and pinnae were the main As pools, storing 75–86% of the total As uptaken by the plants. The rhizome, a `buffer-storage' for plant As, maintained high concentrations of As under high soil As while the pinnae became the most important organ of storing the As under low soil As. Chinese brake might possess the ability of adjusting its As-storage under different soil As levels. The plant can not only hyperaccumulate As from the soils, but also enriched P and Ni from the soils and translocated them to the fronds. It is important to improve the root distribution for phytoremediation of As-contaminated soils using Chinese brake.     

A search for trace elements in some human intracranial tumors by instrumental neutron activation analysis

A investigation was undertaken to measure the presence of trace elements in some intracranial tumors using the instrumental neutron activation analysis technique. The following 20 minor and trace elements were investigated: Na, Mg, Al, P, Cl, K, Ca, Cr, Mn, Fe, Co, Cu, Zn, As, Se, Br, Rb, Sb, I, and Cs. Our results are compared with other trace element analyses in human brain tissue.     

Elemental analysis of herbal preparations for traditional medicines by neutron activation analysis with the k0 standardization method

Medicinal herb preparations prescribed for specific treatment purposes were purchased from markets and were analyzed by instrumental neutron activation analysis withk ₀ standardization. Then, 500–700 mg of each sample was pelletized under a pressure of six tones and irradiated together with monitors for a and neutron flux ratio determinations for about 6 h in a thermal flux of 2.29 x 10¹² n/cm²/s. The accuracy of the method was established by analyzing standard reference materials. Twenty-nine elements, Ag, As, Au, Ba, Br, Ca, Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Mn, Mo, Na, Rb, Sb, Sc, Se, Sm, Sr, Th, U, Yb, and Zn, were measured in all the samples, and Hg was detected in some samples, with good accuracy and reproducibility. The concentration of elements determined was found to vary depending on the composition of the herbs used. Although the trend linking the element of the medicinal plants to its curative abilities could not be clearly determined, this study showed that the toxic elements found in the samples were below the levels prescribed by health regulations. Nevertheless, such data are important to understand the pharmacological action and the exact mechanisms of action and formation of active constituents for each medicinal plant and to decide the dosage of the herbs used in the final formulation.