Influence of nitrogen on the behaviour of nickel in wheat

A glasshouse experiment was conducted to study the effect of Ni on the growth and nutrients concentration in wheat (Triticum aestivum Cv. WH 291) in the presence and absence of applied N as urea. Responses to N application were observed up to 120 g N g^–1 soil. No response to Ni was observed in the dry matter yield of wheat tops (leaves + stem) in the absence of applied N while in the presence of applied N, significant yield increases were obtained at 12.5g Ni g^–1 soil. Nickel was not toxic to wheat up to 50g Ni g^–1 soil in the presence of 120g N g^–1 soil. Nitrogen and Ni concentration in wheat tops and roots increased with increasing levels of applied N and Ni, respectively. Applied Ni had an antagonistic effect on N concentration. Similarly, N reduced the Ni concentration in the wheat tissues. Positive growth responses to Ni were associated with 22 and 15g Ni g^–1 in wheat tops, in the presence of applied N at 60 and 120g N g^–1 soil, while Ni toxicity was associated with 63, 92.5 and 112.5g Ni g^–1 in wheat tops, in the absence and presence of applied N at 60 and 120g N g^–1 soil, respectively.     

Tolerance and bioaccumulation of heavy metals in five populations of Cistus ladanifer L. subsp. ladanifer

The effects of heavy metals on the growth, mineral composition (P, K, Fe and Mn) and metal accumulation of five populations of Cistus ladanifer subsp. ladanifer from NE Portugal were investigated in hydroponic experiments. Plants were exposed to increasing concentrations (0–2000 M) of one of eight heavy metals: Cd, Co, Cr, Cu, Mn, Ni, Pb or Zn. Populations of C. ladanifer, whose origin was ultramafic soils (S and UB) or soils developed on basic rocks (B), showed a higher tolerance to the metals Cd, Co, Cr, and Mn, and a considerable degree of tolerance to Ni. In contrast, populations originating on acid-rock soils (M and SC) showed higher tolerance to the metals Cu and Zn. Populations showed different patterns of metal accumulation and distribution in the plant parts, suggesting different mechanisms of metal tolerance are used. The more Cd-, Co- and Mn-tolerant populations (S, UB, B and SC (Cd)) showed accumulation of these three metals in the shoots (shoot:root metal concentration ratios (S:R) > 1). Shoot concentrations of up to 309 g Cd g^–1, 2667 g Co g^–1 and 6214 g Mn g^–1 were found in these populations. The populations, UB and M, showed considerable tolerance to Ni and Zn, respectively. These populations accumulated up to 4164 g Ni g^–1 and 7695 g Zn g^–1 in their shoot tissues, and these metals were efficiently transported from the roots to aerial parts (S:R > 3 (Ni), S:R > 1 (Zn)). In contrast, the S and SC populations maintained higher growth rates in the presence of Ni and Zn, respectively, but showed exclusion mechanisms of metal tolerance: reduced Ni and Zn transport to shoots (S:R < 1). Cistus ladanifer was not able to efficiently transport Cr, Cu or Pb from its roots to its aerial parts (S:R ranged from 0–0.4). The more Cu-tolerant populations, M and SC, showed a greater restriction of Cu transport to the shoots than the ultramafic- or basic-rock populations. Significant changes in the plant mineral composition were found, however, concentrations were generally above mineral deficiency levels. Based on these preliminary results the possible usefulness of this plant for phytoremediation technologies is discussed. However, further investigations are necessary to evaluate its growth and metal accumulation under soil and field conditions.     

Trace element concentrations in Antarctic krill,Euphausia superba

Whole Antarctic krill, Euphausia superba collected along the Western Antarctic Peninsula, were analyzed for 14 elements. Average element abundances (in parentheses) in g/g, in descending order, were as follows: P(9940), Cu (80.5), Zn (43.5), Fe (28.0), Se (5.80), Ba (3.78), Mn (1.98), As (1.92), Ag (1.71), Ni (0.54), Cr (0.30), Cd (0.29), Pb (0.22), and Hg (0.025). Inverse relationships were found between krill length and Hg concentration as well as between As and P levels. A geographic trend of increasing Mn and P levels from southwest to northeast along the Antarctic Peninsula was Sound. Results were compared to earlier data for evidence of metal concentration changes due to anthropogenic activity over the last 15 years.     

Effect of polyethylene glycol and sugar alcohols on soybean somatic embryo germination and conversion

The effect of different vitamins and inorganic micronutrients on callus growth and the induction and proliferation of somatic embryos from young mature, fully expanded leaves of chilli pepper (Capsicum annuum L.) was investigated. Explants were cultured on a solid Murashige and Skoog (MS) medium supplemented with 8% (w/v) sucrose, 12.9 M 6-benzyladenine, 9 M 2,4-dichlorophenoxyacetic acid and 0.5 mg l^–1 thiamin.HCl in various combinations of eleven different vitamins. Alternatively, explants were cultured onto a solid medium containing MS macro- and micronutrients except for the salts of Mn, Zn, I, Cu and Co which were added at either the standard MS concentration or at a tenfold increased (Cu, Co) or decreased (Mn, Zn, I) concentration. The results indicated that somatic embryogenesis from pepper leaves is favoured by the addition of nicotinic acid to the culture medium and the increase of copper concentration (an average induction of 70.2 globular embryos/mm² of explant surface, 9.2% higher than control), without reducing embryo maturation and germination.     

Superoxide dismutase: An enzyme system for the study of micronutrient interactions in plants

The effect of different Mn levels on the isozyme pattern of superoxide dismutase was investigated. Pisum sativum L. plants were grown in nutrient solutions containing three Mn concentrations: 0.005 g/ml (deficient), 0.05 g/ml (low), and 0.5 g/ml (optimum). Leaf extracts contained three electrophoretically distinct superoxide dismutases (SOD), two of which were inhibited by cyanide and were probably Cu-Zn-SODs, while the third one was CN-insensitive and could be either an Mn- or an Fe-SOD. At 0.005 g/ml Mn supply the CN-insensitive SOD was significantly depressed at 15, 30, and 45 days of growth, whereas at 0.05 g/ml Mn this isozyme was significantly decreased only at 45 days growth. The two CN-sensitive SODs were inversely related to the CN-resistant enzyme, the activities of the former enzymes being significantly increased at Mn-deficient levels throughout plant growth. Metal determinations of the plants showed that at low concentrations of Mn in the nutrient media, copper and zinc content of leaves increased: the lower the Mn level, the higher the increase produced. The CN-resistant SOD activity, as judged by its dependency on Mn, appears to be an Mn-SOD rather than an Fe-SOD. In the light of the results obtained, the use of the enzyme system superoxide dismutase for the study of the role and interactions between Mn, Cu, and Zn in the plant cell is proposed.Abbreviations EDTA ethylenediaminotetraacetic acid - NBT nitro blue terazolium - SOD superoxide dismutase (EC 1.15.1.1)     

Seasonal Variability in the Levels of Fe, Zn, Cu, Mn, and Cd in the Hepatopancreas of the Japanese Scallop Mizuhopecten yessoensis

The relationships between concentrations (g/g of tissue) and content (g/organ) of the metals Fe, Zn, Cu, Mn, and Cd with seasonal changes in the weight of the hepatopancreas in the Japanese scallop Mizuhopecten yessoensis are studied. It is shown that, during a year, the weight of the hepatopancreas in the mollusk shows significant (more than twofold) changes. A positive correlation is revealed between the seasonal changes in the concentrations of the physiologically important metals Fe, Zn, Cu, and Mn and the weight of this organ, although no general consistent pattern of seasonal variability in the metal concentrations is found. For toxic Cd, a negative correlation is found between its concentration and the weight of the hepatopancreas.     

Tolerance and bioaccumulation of copper in Phragmites australis and Zea mays

The effects of copper on the growth, tolerance indices, mineral composition (N, P, K, Fe, Zn and Mn) and metal uptake of reed (Phragmites australis [Cav. Trin. ex Steudel]) and maize (Zea mays L.) were investigated in hydroponic experiments at copper concentrations ranging from 0.5 to 157 M Cu. A reduction in root length was shown to be a good indicator of copper toxicity, concentrations of 15.7 and 78.7 M Cu inhibiting root growth in maize and reed, respectively. The reed was significantly more tolerant of copper than maize and at 7.85 M Cu (external concentration), reed can be described as a Cu tolerant plant, and maize as a Cu non-tolerant species. As a result of Cu toxicity, the concentrations of macronutrients N, P and K decreased in both shoot and root of maize, while the concentrations were hardly affected in reed tissues. Fe concentration increased in shoots and roots of maize and in roots of reed with increasing Cu treatments, leading to highly significant (p<0.01) linear relationships between tissue Fe and Cu concentrations. The bioconcentration factor (BCF) of Cu was higher in roots than in shoots of both plant species, ranging from 612 to 1592 in reed for the Cu treatments tested. In the roots of maize, BCF of Cu increased from 349 to 1931 when increasing Cu in nutrient solution from 7.85 M to 78.5 M. Therefore, reed could be useful in wastewater treatments for the removal of Cu. However, the use of reed in phytoextraction of Cu from contaminated soils is limited by the low accumulation rate in shoots and although reed can be more efficient than maize for Cu phytoextraction, harvesting the full biomass, including roots, may be required.     

Rapid Axillary Bud Proliferation and ex vitro Rooting of Eupatorium triplinerve

Effective protocol was established for micropropagation of the medicinal plant Eupatorium triplinerve Vahl through rapid axillary bud proliferation and ex vitro rooting. Murashige and Skoog (MS) medium fortified with 8.87 M benzylaminopurine (BAP) and 2.46 M indole-3-butyric acid (IBA) was the best for axillary bud proliferation and developed a mean of 8.1 shoots per node. Excision and culture of the node segments of the in vitro shoots on medium supplemented with the same concentration of growth regulators developed more than 30 shoots within 40 d. Shoot multiplication did not exhibit decrease in the number of shoots even at 7^th subculture. Dipping of the basal end of shoots in 2.46 M IBA solution for 10 d induced roots and its transfer to small pots facilitated the survival of all rooted shoots (100 %). Ex vitro rooting by direct transfer of the shoots from multiplication medium showed 92 % survival.     

Thidiazuron-Induced High-Frequency Shoot Regeneration from Root Region of Robinia pseudoacacia L. Seedlings

High-frequency regeneration of shoots was achieved at root region of seedlings of Robinia pseudoacacia L. cultured from seeds on medium supplemented with thidiazuron (TDZ, 1.0 M). The roots of intact seedlings proliferated and formed a compact callus followed by differentiation of numerous shoots. Corresponding cultures on benzylaminopurine-containing medium exhibited much weaker response. Hypocotyl segments also formed shoots at a lower concentration of TDZ (0.1 M). The shoots formed on TDZ-containing medium were well-developed and readily rooted on hormone-free medium. The obtained plants after acclimation in culture room survived after transfer to soil.     

6-Methylpurine-induced inhibition of sclerotia morphogenesis in Sclerotium rolfsii and its reversal by adenosine

In liquid synthetic medium inoculated with Sclerotium rolfsii (SR), addition of 6-methylpurine (MP, 50g/ml) immediately after inoculation led to approximately 100% reduction in sclerotia production. Adenosine, and to a lesser extent guanosine, each at final concentration of 100g/ml significantly reduced inhibition of sclerotia formation by SR in presence of 50g/ml MP. Uridine and cytidine each at 100g/ml had no such effect. The inhibition of sclerotia morphogenesis could be prevented by addition of 800g/ml of adenosine together with 50g/ml MP. Reversal by adenosine of MP-induced inhibition of sclerotia development was concentration dependent.     

Effect of various metal ions on growth of two wheat lines known to differ in aluminium tolerance

The effects of aluminium (Al), manganese (Mn), zinc (Zn), copper (Cu), boron (B), iron (Fe), gallium (Ga), scandium (Sc) and lanthanum (La) on growth of an Al-tolerant and an Al-sensitive line of wheat (Triticum aestivum L.) were measured in solution culture. The concentrations of nutrients in the basal nutrient solution were (M) 500 Ca, 100 Mg, 300 K, 600 N (150 NH₄, 450 NO₃), 600 SO₄, 2.5 P, 3 B, 2.5 Fe, 0.5 Zn, 0.5 Mn, 0.1 Cu at a pH of 4.7. The major solution nutrient concentrations were maintained at the nominal concentration with monitoring, frequent additions and weekly renewal. Differentiation in yield between the Al-tolerant and Al-sensitive line only occurred in the presence of Al indicating that, in the long term, none of the other metals tested could be used as an analog for Al. The visual symptoms in the roots of Cu toxicity (in both lines) and Al toxicity (in the sensitive line) were similar. The solution concentration (M) at which yield of the roots of the tolerant line was reduced by 50% was, in order of increasing tolerance, Cu 0.5, Sc 1.1, La 7.1, Ga 8.6, Al 15, Zn 19, Fe 84, B 490 and Mn 600.     

Geochemical cycling of heavy metals in a marine coastal area: benthic flux determination from pore water profiles and in situ measurements using benthic chambers

Concentrations of the heavy metals Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn were measured in sea water, suspended matter, sediments and pore water samples collected in a coastal area of the middle Tyrrhenian Sea. Concentration factors between pore water (extracted from the first centimeter of the sediments) and the overlying sea water (taken 30 cm above the sea bed) were less than 1 for Cr, Cu and Pb, 1–10 for Cd and Ni, 10–100 for Fe and Co, 100–1000 for Mn, and 1–100 for Zn.The benthic fluxes of heavy metals at the sediment-water interface were measured directly using in situ benthic chambers and calculated using Fick's first law during two experimental periods, one in 1986 and the other in 1988. The fluxes of Cu, Ni, Pb and Zn varied significantly over time; this appeared to be related to their relatively low ( 10) concentration factors. From the benthic chamber experiments, metals with positive fluxes were in the order: Mn > Fe > Co > Cd, while those with negative fluxes were: Zn > Pb > Ni Cu. Fluxes calculated using Fick's Law were: positive – Mn > Fe > Zn (or Zn > Fe) > Ni > Co > Cd, negative fluxes Pb > Cu > Cr.Measured (benthic chamber) and calculated (Fick's first law) fluxes for Co, Cd, Mn, Pb and Fe were comparable within an order of magnitude, although less agreement was found for Cu, Ni and Zn. Removal of Ni and Zn at the sediment-water interface has been proposed to explain the fact that the measured and calculated fluxes have opposite directions for these metals.     

In vitro culture of Vitis: the effects of light spectrum,manganese sulfate and potassium iodide on morphogenesis

The effects of blue and red light, manganese sulfate concentration (100 and 5 M), and potassium iodide (5 and 0 M) on shoot and root production from subcultured shoots of the Vitis hybrid Remaily Seedless were studied.Shoot production was greater in blue light. It was increased by lowering the manganese sulfate concentration. The response to manganese in blue light was greatest when there was no potassium iodide addition.Root production was decreased by red light and lower manganese concentration.The effects of manganese, iodide and light spectrum on morphogenesis are discussed in relation to their known effects on IAA metabolism.     

Copper in plant species in a copper gradient in Catalonia (North East Spain) and their potential for phytoremediation

The accumulation of Cu in roots and shoots of 32 plant species growing on soils with a wide range of Cu concentrations (30–18 500 g g^–1 total soil Cu) located in Collserola Mountain (Barcelona, Spain) was analysed. High Cu availability decreased the species diversity in the Hyparrhenietum hirto-pubescentis, the natural plant association at the study sites. Shoot and root Cu concentrations in relation to extractable soil Cu concentrations were used for the evaluation of the Cu resistance strategy in the different species. Saturation of Cu accumulation in roots was observed in most species. Hyparrhenia hirta was the most efficient shoot excluder, while the linear increase of shoot Cu with the Cu soil concentration exhibited the highest slope in Hirschfeldia incana. Most species accumulated more Cu in roots than in shoots. High shoot/root Cu ratios were only found in the highly Cu-resistant Hirschfeldia incana, in the resistant or moderately resistant Spartium junceum and Reseda sp. (R. lutea and R. phyteuma), and in the much less resistant Ononis natrix. Only two species, Hirschfeldia incana and Sedum sediforme were able to support the extreme Cu-toxicity conditions on soils with 5000–16 800 g g^–1 extractable Cu. Among the grass species tested Hyparrhenia hirta was the most Cu-resistant species (up to 1950 g g^–1 extractable soil Cu). The potential usefulness of these pseudometallophytes for phytoremediation of Cu-contaminated soils is discussed.     

Comparison of Ni-sensitive and Ni-resistant strains of Nostoc muscorum

A wild-type Ni-sensitive (Ni^s) strain of Nostoc muscorum ISU spontaneously yielded mutants resistant to inhibition by 40 M Ni with a frequency of about 10^-7. A Ni-resistant (Ni^r) mutant was deficient in the activities of urease and uptake hydrogenase. Cellular Ni uptake in the Ni^s strain was dependent on concentration (40 to 120 M) and time (0 to 30 min) (V_max=0.51 nmol/g protein.min; K_m=92 M). The Ni bioconcentration factor for such cells ranged between 0.95×10³ and 1.89×10³. Ni uptake in spheroplast preparations from Ni^s cells followed almost the same trend as intact cells except that the bioconcentration factor was slightly less [(0.82 to 1.39)×10³]. In contrast, Ni uptake in the Ni^r intact cells was not concentration dependent and also the uptake was saturated, even at 40 M, within 10 min. Spheroplasts from the Ni^r strain showed a Ni bioconcentration factor of 1.19×10³ compared with 4.41×10³ for intact cells. The invariably lower Ni uptake by spheroplasts was attributed to altered membrane transport properties.R.K. Asthana, A.L. Singh and S.P. Singh are with the Algal Research Laboratory, Centre of Advanced Study in Botany, Banaras Hindu University, Varanasi-221 005, India.     

Phytoavailability of Cd and Zn in soil estimated by stable isotope exchange and chemical extraction

The distribution of labile Cd and Zn in two contrasting soils was investigated using isotopic exchange techniques and chemical extraction procedures. A sewage sludge amended soil from Great Billings (Northampton, UK) and an unamended soil of the Countesswells Association obtained locally (Aberdeen, UK) were used. ¹¹⁴Cd and ⁶⁷Zn isotopes were added to a water suspension of each soil and the labile metal pool (E-value) determined from the isotope dilution. Samples were obtained at 13 time points from 1h to 50 days. For the sewage sludge amended soil, 29 g Cd g^–1 (86% of total) and 806 g Zn g^–1 (65% of total) were labile and for the Countesswells soil the value was 8.6 g Zn g^–1 (13% of total); limits of detection prevented a Cd E-value from being measured in this soil. The size of the labile metal pool was also measured by growing plants for 90 days and determining the isotopic content of the plant tissue (L-value). Thlaspi caerulescensJ. & C. Presl (alpine penny cress), a hyperaccumulator of Zn and Cd, Taraxacum officinale Weber (dandelion) and Hordeum vulgare L. (spring barley) were used. L-values were similar across species and lower than the E-values. On average the L-values were 23±0.8 g Cd g^–1 and 725±14 g Zn g^–1 for the Great Billings soil and 0.29±0.16 g Cd g^–1 and 7.3±0.3 g Zn g^–1 for the Countesswells soil. The extractable metal content of the soils was also quantified by extraction using 0.1 M NaNO₃, 0.01 M CaCl₂, 0.5 M NaOH, 0.43 M CH₃COOH and 0.05 M EDTA at pH 7.0. Between 1.3 and 68% of the total Cd and between 1 and 50% of the total Zn in the Great Billings soil was extracted by these chemicals. For the Countesswells soil, between 6 and 83% of the total Cd and between 0.1 and 7% of the total Zn was extracted. 0.05 M EDTA and 0.43 M CH₃COOH yielded the greatest concentrations for both soils but these were less than the isotopic estimates. On the whole, E-values were numerically closer to the L-values than the chemical extraction values. The use of isotopic exchange provides an alternative estimate of the labile metal pool within soils compared to existing chemical extraction procedures. No evidence was obtained that T. caerulescens is able to access metal within the soil not freely available to the other plants species. This has implications for long term remediation strategies using hyperaccumulating plant species, which are unlikely to have any impact on non-labile Cd and Zn in contaminated soil.     

Trace metal and vitamin requirements of Methanococcoides methylutens grown with trimethylamine

Trace organic nutrient and metal requirements for the growth of Methanococcoides methylutens strain TMA-10 were determined in defined medium that contained trimethylamine as the substrate. Biotin was the only organic supplement required in place of yeast extract, Trypticase or a mixture of 8 B-vitamins. Fe an Ni were required for growth and low concentrations of Fe²⁺ (<5 M) and Ni²⁺ (<0.25 M) provided limited growth. In the absence of added Co the growth rate was reduced by 94% and growth was limited at concentrations below 0.1 M. Stimulation of growth by Se, Mo, B, Al, Zn, Mn or Cu could not be demonstrated.     

Seedling responses of three Australian tree species to toxic concentrations of zinc in solution culture

A frequently desired outcome when rehabilitating Zn toxic sites in Australia is to establish a self-sustaining native ecosystem. Hence, it is important to understand the tolerance of Australian native plants to high concentrations of Zn. Very little is known about the responses of Australian native plants, and trees in particular, to toxic concentrations of Zn. Acacia holosericea, Eucalyptus camaldulensis and Melaleuca leucadendra plants were grown in dilute solution culture for 10 weeks. The seedlings (42 days old) were exposed to six Zn treatments viz., 0.5, 5, 10, 25, 50 and 100 M. The order of tolerance to toxic concentrations of Zn was E. camaldulensis> A. holosericea> M. leucadendra, the critical external concentrations being approximately 20, 12 and 1.5 M, respectively. Tissue Zn concentrations increased as solution Zn increased for all species. Root tissue concentrations were higher than shoot tissue concentrations at all solution Zn concentrations. The critical tissue Zn concentrations were approximately 85 and 110 g g^–1 DM for M. leucadendra, 115 and 155 g g^–1 DM for A. holosericea and 415 and 370 g g^–1 DM for E. camaldulensis for the youngest fully expanded leaf and total shoots, respectively. The results from this paper provide the first comprehensive combination of growth responses, critical external concentrations, critical tissue concentrations and plant toxicity symptoms for three important Australian genera, viz., Eucalyptus, Acacia and Melaleuca, for use in the rehabilitation of potentially Zn toxic sites.     

In vitro plant regeneration from callus derived from root explants of Lathyrus sativus

Protocols have been developed for the in vitro production of plants from callus derived from root explants of Lathyrus sativus cv. P-24. Callus and shoot regeneration were achieved only in MS medium supplemented with 10.7 M naphthaleneacetic acid and an increased concentration of kinetin (0.9 M for 14 days to 1.4 M for 18 days) during callusing. The shoots obtained rooted in 1/2 MS supplemented with 0.5 M indolebutyric acid. During the year plants have been regenerated several times. The requirement for growth regulators is very specific and narrow.Abbreviations IAA indoleacetic acid - IBA indolebutyric acid - NAA naphthaleneacetic acid - BA benzyladenine     

The bactericidal effects of Lactobacillus acidophilus,garcinol and Protykin® compared to clarithromycin,on Helicobacter pylori

Chronic infection with Helicobacter pylori causes peptic ulcers, gastric cancer and lymphoma. We evaluated the inhibitory effects of the probiotic Lactobacillus acidophilus DDS-1J, the antibiotic clarithromycin and the natural antioxidants garcinol and Protykin^® (containing 50% trans-resveratrol) on Helicobacter pylori strain ATCC 49503. The findings of this study indicate that Lactobacillus acidophilus DDS-1J exerts a growth inhibitory effect on H. pylori at a ratio of 1:1 or higher in vitro. In the case of clarithromycin, garcinol and resveratrol, the bactericidal effect is time and concentration dependent. Clarithromycin completely inhibited growth at 62.5 g/ml at 6 h and at 31.5 g/ml at 12 h. For garcinol the highest concentration needed for complete inhibition was 31.5 g/ml at 6 h and 3.9 g/ml after 12 h incubation. For resveratrol, significant inhibition was noted at 1000 g/ml at 12 h only. The bactericidal effect of garcinol was reduced by the addition of resveratrol at all concentrations 125 g/ml at 6 and 12 h. We conclude from this study that Lactobacillus acidophilus DDS-1J inhibits H. pylori at 1:1 and higher ratios. Also, between the two antioxidants, garcinol is much more potent than resveratrol as a bactericidal agent against H. pylori, and that resveratrol may antagonize this effect. Finally, our study showed equivalent or better bactericidal activity of garcinol compared to clarithromycin against H. pylori at 6 and 12 h incubation, indicating a potential role for this antioxidant in treatment for H. pylori infection.