Phytoplankton in reservoir R-11 of Techa reservoir cascade of Industrial Association "Maiak"

Phytoplankton of reservoir R-11 was investigated at vegetative seasons of 2007 and 2008. R-11 is a locking reservoir in the cascade of Mayak PA reservoirs. The specific activity in water of R-11 ranged from 0.9 to 1.8 kBq/dm for 90Sr and from 0.98 to 3.97 kBq/dm3 for 137Cs; in bottom sediments it ranged from 20 to 400 kBq/kg for 90Sr and from 0.35 to 220 kBq/kg for 137Cs. Concentration of SO4- exceeded the maximum permissible concentration for fishing reservoirs in 5-7 times. The content of 90Sr in the phytoplankton has made 400 kBq/kg (for dry weight), and 137Cs--2.20 kBq/kg (for dry weight). The absorbed dose of irradiation for the phytoplankton calculated under the content of 137Cs and 90Sr in water and in phytoplankton (the external irradiation from activity of bottom sediments was not considered) has made 901 mGy per year. Altogether the phytoplankton of reservoir R-11 included 107 species. Such species of Cyanobacteriae as Oscillatoria agardhii Gom. was the dominant in phytoplanktonic community. Another Cyanobacteriae, Lyngbya limnetica Lemm. and Aphanizomenonflos-aquae (L.) Ralfs. acted the most important part in a complex of species-subdominants. According to quantitative development of the phytoplankton the reservoir R-11 can be classified as P-mezosaprobe waters.     

Assessment of radiation exposure level for hydrobionts in some special industrial ponds at the "Mayak" PA

Evaluation of the radionuclide content in the ecosystem components (water, sediments, aquatic organisms) of industrial reservoirs-storages of liquid radioactive waste of the "Mayak" PA (reservoirs R-4, R-10, R-11, R-17, R-9) and the estimation of the absorbed dose rate in aquatic organisms of these reservoirs using the software package ERICA Assessment Tool 1.0 May 2009 have been performed. Gradient of the absorbed dose rate for the detected taxonomic groups of hydrobionts in the series of the studied reservoirs R-11 --> R-10 --> R-4 --> R-17 --> R-9 was almost equal to one order of magnitude. The estimated absorbed dose rate for phytoplankton ranged from 5.4 x 10(0) mGy/day (R-11) to 4.0 x 10(4) mGy/day (R-9), for zooplankton--from 6.4 x 10(-1) mGy/day (R-11) to 3.8 x 10(3) mGy/day (R-9), for zoobenthos (chironomids)--from 5.6 x 10(0) mGy/day (R-11) to 1.1 x 10(3) mGy/day (R-17), for fish (roach)--from 8.0 x 10(-1) mGy/day (R-11) to 1.9 x 10(1) mGy/day (R-4).     

Life-history traits of a tube-dwelling corophioid amphipod, Paracorophium excavatum, exposed to sediment copper

This is the first demonstration that sediment contaminants can influence the reproduction of amphipods. Groups of Paracorophium excavatum from a slightly contaminated estuarine site were held within laboratory mesocosms containing four copper-spiked estuarine sediments (Cu 14-46 μg g⁻¹ dry weight) and a control sediment (Cu 5 μg g⁻¹ dry weight) at 15 °C for 28 days. Copper sediment concentration did not affect the amphipod sex ratio. Female maturation was inhibited within copper-spiked sediments but female length was similar. Juvenile recruitment occurred only in sediments containing less than 20 μg g⁻¹. Males were significantly larger than females in the control sediment (Cu 5 μg g⁻¹ dry weight) and male length decreased linearly with increasing copper concentration. The copper concentration within whole body tissues increased with dry body dry weight in all sediments except the highest copper concentration. Following 28 days of exposure, none of the female amphipods from the copper-dosed sediments was brooding embryos. In contrast, brood size of females in the control sediment (Cu 5 μg g⁻¹) was similar to field samples. Because low concentrations of sediment copper affect the maturation and growth rates of male and female amphipods differently, these life-history traits could affect the population structure of amphipods exposed to copper contaminated sediments.     

Increase of Scopolamine Production by High Density Culture of Duboisia myoporoides Roots

A circulation culture system was established for the high density root culture of Duboisia roots. It consists of a vessel for root culture, an aeration tube, a medium reservoir, and a peristaltic pump. Medium saturated with pure oxygen was circulated continuously through the culture vessel and the medium reservoir, and was pumped back into the aeration tube by the pump. Duboisia roots could be cultured at densities of up to 120g dry weight (DW) dm^?3 with no decrease in scopolamine content, this density being about 20 times the amount that can be used in ordinary flask culture. The final scopolamine yield at the end of 3 weeks was 1350mgdm^?3.     

The carbohydrate management of leaves of prunus laurocerasus L. at low and Sub-Freezing temperatures

The changes n dry weight and in the content of sugars and starch of leaves of the evergreen species Prunus laurocerasus L. were studied in the field and in laboratory conditions. The leaves of field-grown bushes as well as those kept under controlled conditions were analyzed at one week intervals at the end of the winter and in early spring from March 11 to May 6, 1970, The effect of four different temperature regimes was compared (day/night) : A : — 2 to — 6 °C/ — 6°C. B: 6°C/ —6°C, C: 6 °C/6 °C and D: 12 °C/ — 6 °C. During the whole experimental period of 56 days a net increase in dry weight 246.84 mg dm^-2, i.e. 21.7 % was found under field conditions. A negative balance in assimilate management was recorded only during the one week period. The total content of sugars decreased from 11.68 % to 6.42 % while the content of starch rose from zero to 3.12 %. The net increase in dry matter found under controlled conditions was 6.69 (A), 4.68 IB). 6.88 (C) and —0.43 (D) mg dm^-2 d^-1.     

Aquatic macroinvertebrate community structure of aNymphoides peltata-dominated and macrophyte-free site in an oxbow lake

The aquatic macroinvertebrates in two freshwater biotopes,viz. aNymphoides peltata-dominated site and a macrophyte-free site, were studied quantitatively in a shallow alkaline oxbow lake of the river Waal, the main branch of the river Rhine in The Netherlands. The research comprised the analysis of water, sediment and macrophyte samples.In the macrophyte-free site Oligochaeta and Nematocera, particularly of the collector gatherer functional feeding group, dominated the prevailing benthic community. The total macroinvertebrate biomass ranged here from 0.3 to 0.9 g ash-free dry weight per m² of biotope.Species richness, densities, and biomass of macroinvertebrates were considerably higher in the biotope dominated byNymphoides peltata. Many taxa were found associated with the aboveground macrophyte. The sediment compartment, however, contributed most to the total density and biomass of macroinvertebrates. Nematocera and Oligochaeta were the most abundant fauna groups, whereas the largest share in total biomass was provided by clams (Mollusca). The biomass of the total macroinvertebrate community in theNymphoides-dominated site ranged from 6.2 to 7.5 g ash-free dry weight per m² of biotope. The biomass of the aboveground phytophilous fauna ranged from 0.1 to 0.6 g ash-free dry weight per m² of biotope. In September, when theNymphoides peltata vegetation was in its senescent phase, the largest numbers and the highest biomass of phytophilous macroinvertebrates were observed. The contribution of the shredder functional feeding group was high in this period. This, and the overall high abundance of fauna with a detritivorous mode of life, indicates the importance of macrophyte detritus as input to food chains.     

Sampling Design and Enumeration Statistics for Bacteria Extracted from Marine Sediments

The spatial and temporal distributions of marine bacteria were studied at both a muddy and a sandy subtidal site in North Inlet, S.C. The sampling design was hierarchical, since subsampling (by a dilution series) of the sediments was necessary to count bacterial cells using acridine orange epifluoresence microscopy. The cell count data fit a log-normal distribution. The abundance of bacteria was 10¹¹ g⁻¹ (dry weight) of mud and 10⁹ g⁻¹ (dry weight) of sand. Variance component analyses demonstrated that variation due to the subsampling procedures was always statistically significant. Thus the common practice of counting 20 fields from one filter preparation is inadequate for estimating the true bacterial population variance in marine sediments. It is recommended that replication of the subsampling level be performed. Standardization of data (by dry weight of sediment) decreased sampling variance at the mud site but not at the sand site, implying that bacteria are more homogeneously distributed in sand than in mud.     

Bacterioplankton and Bacteriobenthos of Three Floodplain Lakes in the Lower Course of the Amur River

The main structural and functional characteristics of bacterioplankton and bacteriobenthos of three lakes in the lower course of the Amur River are presented: the total number of bacteria (TNB), biomass, the numbers of bacteria of certain aerobic and anaerobic groups; the intensities of methanogenesis (MG), methane oxidation (MO), assimilation of ¹⁴C-compounds, sulfate reduction (SR); and gross estimate of organic matter decomposition (D). Depending on the reservoir type and the anthropogenic load, TNB constituted (2.27 to 16.1) × 10⁶ cells/ml in water and (1.06 to 10.35) × 10⁹cells/cm³ in sediments; MO was 0 to 0.28 ml CH₄/(l day) in water and 0 to 8.4 ml CH₄/(dm³ day) in sediments; MG in sediments was 0.001 to 40 ml CH₄/(dm³ day); SR varied from 0.001 to 24.8 mg S/(dm³ day); D was 0.3 to 25 g C/(m² day) in water and 0.2 to 4.9 g C/(m² day) in sediments. The role of anaerobic microbial processes of organic matter decomposition was shown to increase with an increase in the anthropogenic load, attaining 95% of the total D in the ecosystem of an accumulating pond.     

Production and distribution of dry matter in trees of Coffea arabica L. in Kenya as affected by seasonal climatic differences and the presence of fruits

Standard growth analysis procedures were used to study the production and distribution of dry matter in 3 1/2 to 5-year-old coffee trees through their first and into their second commercial fruiting year. The trees were growing in the field and were treated according to normal commercial practice. Up to fifteen fruiting and deblossomed trees were harvested on each of seven occasions, at intervals of 63–90 days. The dry weights of four aerial fractions, five root fractions and all fallen, picked and pruned material were recorded. The net assimilation rate (E) of deblossomed trees was as large as that recorded in East Africa for coffee seedlings (0·13 g dm^-2wk^-1). Fruiting trees increased in dry weight faster than deblossomed trees, even when their leaf area was 30% smaller. Their E was up to 0·19 g dm^-2wk^-1when expressed on a leaf area basis and up to 0·16 g dm^-2wk^-1even when the total green fruit surface area was included in the calculation. In the hot, dry season, January–February 1968, all parts of the trees increased in dry weight relatively slowly, except the thin roots (< 3 mm diameter) which, in this season, took about 10% of the dry weight increment. The trees had been pruned in December and E of deblossomed trees was only 0·09 g dm^-2wk^-1. Flushes of shoot growth occurred at the beginning of the Long Rains 1967 and 1968 (February–March). During the 1967 shoot growth flush, 61% of the dry weight increment was used in the production of new, large leaves with a mean specific leaf area of over 140 cm²g^-1. The thin roots took about 10 % of the increment, but the thicker roots increased in weight very slowly. The branches and trunk extended rapidly, but their radial growth was relatively slow. Following the shoot growth flushes, the leaf area ratio of the trees was large (0·38 dm²g^-1in 1967) and during the Long Rains (April–June 1967, 1968), when conditions were favourable for photosynthesis (E 0·13 g dm^-2wk^-1), all parts increased in dry weight relatively rapidly, although in 1968 the thin roots took as little as 3 % of the total increment. Leaf area ratio decreased during the Long Rains owing to a large decrease in specific leaf area (in 1967: 118 to 95 cm²g^-1). Pruning was carried out in June and new leaf production during the cool, dry season, July to mid-September, was very slow. Consequently, the total dry weight increase of the trees during this season was relatively small, although the E of deblossomed trees was 0·13 g dm^-2wk^-1. The leaves, which took 33 % of the increment, decreased further in specific leaf area (to 83 cm²g^-1) and most root fractions increased in dry weight rapidly, the thin ones taking 17 % of the increment. Light fruiting in 1967 did not affect the seasonal periodicity in growth described. Both light and heavy fruiting tended, eventually, to lessen the dry weight increase of leaves and thin roots proportionately more than that of the trunk and thick roots. In 1968 fruiting trees retained over 8000 fruits per tree, which took over 70 % of the dry weight increment during the 1968 Long Rains, and became 36 % of the trees' dry weight. Some rootlets on these trees decreased in weight. Aspects of the productivity, growth periodicity and fruiting of coffee are discussed, and some management implications are noted.     

The relationship between leaf canopy development and yield of barley

A study was carried out into the relationship between sowing date, canopy development and yield of four barley genotypes sown in autumn and spring. Yield was considered as the product of PAR absorbed by the crop canopy up till anthesis, the dry matter: radiation quotient, the ratio of grains m²at maturity to the weight of the crop at anthesis and the mean grain weight. Equations were derived to predict the time course of the proportion of PAR absorbed in relation to date of sowing using thermal time as predictor. In crops that were not short of water and were fully vernalised, genotypic differences were detected in plant population density, date of anthesis, and the four yield components identified above. All attributes except plant population density were affected by shortage of water but genotypes differed in their response.     

Sediment Distribution of Methanogenic Bacteria in Lake Erie and Cleveland Harbor

The direct fluorescent-antibody technique was employed to determine the distribution patterns of four species of methanogens in the sediments of Lake Erie and Cleveland Harbor. Methanobacterium ruminantium was the most numerous methanogen found in regions of high-organic-silt sediments. The population of this species ranged from 10⁶ to 10⁹ cells/g of dry sediment. Methanobacterium strain MoH and Methanosarcina barkeri were identified in sand-silt, clay, or sand sediments. These methanogens ranged in density from 10⁶ to 10⁷ cells/g of dry sediment. Methanospirillum hungatii was observed only after an organic enrichment was performed on Cleveland Harbor sediments. The seasonal and selective sediment distribution of these methanogens appears to be related to the type and concentration of carbon as substrate as well as to the activities of heterotrophic and sulfate-reducing bacteria.     

Aspects of nitrogen uptake and distribution in maize

The amount of nitrogen (N) taken up after treatment decreased by nearly 50% when either the top five or middle four leaf laminae of maize (Zea mays) plants were removed shortly after flowering, and by 70% when both the middle four and bottom six laminae were removed, but the amount of N moving from the remaining parts of the shoot to the grain did not change much. When all the laminae were removed little N was taken up and only 35% as much N as in untreated plants moved from the shoot to the grain. Removal of all the laminae increased the N content per cent of dry weight of both grain and shoot at final harvest, but the other treatments did not have much effect on the N concentration of any of the parts of the shoot. Plants bearing grain, whether intact or with alternate laminae removed (half-defoliated) at the time of flowering, took up N approximately in proportion to their increase in dry weight during the 4 wk after flowering. The N taken up went to the ear (husks, core and grain) and so did N from the stem and leaves. Intact and half-defoliated plants with no developing grains, because pollination had been prevented, took up no N during this period, though they accumulated about as much dry matter as did plants with grain; the N increment of the husks and core was supplied by the stem and leaves. At final harvest total and grain N content of plants per unit area of land increased by 20 and nearly 30%, respectively, with increase in population between 2·3 and 6·1 plants/m², but apparently fell slightly with further increase of population to 7·4 plants/m². Until shortly after flowering N uptake was rapid enough to maintain similar N contents per cent of dry weight of the parts of the shoot in all populations. Uptake continued at a steady rate, though a slower one than before flowering, until near the time of final harvest in the most widely spaced population. In the denser populations uptake slowed down progressively after flowering, and in the densest population it apparently ceased a few weeks before final harvest. The N concentration of the grain of maturing plants fell with increase of population, but not that of the other parts of the shoot. At final harvest N content of the grain decreased from 1·6% in the most widely spaced to 1·2% in the densest population. That of the rest of the shoot varied between 0·70 and 0·79%. Between 6 and 18 wk after sowing, N content per unit area of green parts of the leaf laminae decreased only slightly, changing from about 20 to 18 mg/dm² with 2·3 plants/m², 18 to 16 mg/dm² with 3·5 plants/m², and 16 to 13 mg/dm² in populations between 4·8-7·4 plants/m².     

Effects of grazing on the quantity and quality of freshwater Aufwuchs

Qualitative and quantitative measures of the Aufwuchs (scum flora) on artificial substrates in situ were used to evaluate the effects of grazing by freshwater pulmonate snails in a shallow pond in southeastern Michigan. Grazer densities of 216 snails/m² marked reduced standing crop so that after 45 days grazed substrata had 6.46 mg dry weight, 604 µg C and 4.18 µg chlorophyll a as compared to controls with 30.62 mg dry weight, 3699 µg C and 6.29 µg chlorophyll a, all on a per dm² basis.Grazing did not change carbon per mg dry matter but caused significant increases in both µg chlorophyll a (control, 0.206; and grazed, 0.649 µg chlorophyll a/mg dry weight, P < 0.01) and nitrogen (control, 8.3; and grazed, 24.2 µg N/mg dry weight, P < 0.001) after 45 days. Both abundance and diversity of the attached community was reduced by grazing from 24 taxa and 80,889 individuals/cm² on control to 8 taxa and 501 individuals/cm² on grazed substrates. Mean productivity of the Aufwuchs was significantly (P < 0.001) reduced by grazing from 76.3 µg C/(dm²·day) on control to 17.7 µg C/(dm²·day) on grazed substrata.Snails were very efficient at clearing smooth surfaces of living cells, detritus, and particulate inorganic matter. There was little evidence of selectivity except for an apparent inability to remove some of the smallest cells (e.g. Cocconeis sp.) probably for mechanical reasons.     

Biomass Measurement of Methanogens in the Sediments of Tokyo Bay Using Archaeol Lipids

An archaeal ether-linked lipid, archaeol, was determined to be a biomass indicator for methanogens both in the laboratory enriched culture and in marine sediments. The archaeol measurement method described by Ohtsubo et al. in 1993 was modified and applied to marine sediments. We compared the amount of archaeol with the cell number of methanogens or methane concentration in laboratory enriched culture of methanogens from marine sediment. Good correlations were obtained as follows: (Methane, mmol) = 11.2 × (Archaeol, mg): r= .996 or (Cell number) = 1.13 × 10¹¹× (Archaeol, mg): r= .995, respectively. In the sediments of Tokyo Bay, archaeol was measured from approximately 46 to 561 ng/dry g sediment at the entrance to 267 to 4160 ng/dry g sediment at the innermost area. Using the coefficient from the laboratory experiment, these data corresponded to cell numbers of 5.2 × 10⁶ to 4.7 × 10⁸/dry g sediment. These values were 1 or 2 orders of magnitude higher than those obtained by culture methods in previous studies. Although dead or decomposed cells might be detected, archaeol measurement is useful for estimating the biomass of methanogens because of the good correlation between methane concentration and archaeol content in marine environments. In this study, we found a correlation of (Methane, mmol) = 0.012 × (Archaeol, mg): r= .932, n= 17 in marine sediments. Received December 21, 1998; accepted June 16, 1999     

Utilization of cyanobacteria by Brachionus calyciflorus: Anabaena flos-aquae (NRC-44-1) as a sole or complementary food source

The rotifer Brachionus calyciflorus can utilize the cyanobacterium Anabaena flos-aquae as either a sole or supplementary food source in laboratory culture. Positive population growth rates accompany food densities of 10 or 100 µg dry weight ml^–1, but slightly negative rates are found at a lower density (1.0 µg ml^–1). These results are consistent for rotifers feeding on two strains of A. flos-aquae, UTEX-1444 and NRC-44-1, with slightly enhanced survivorship and reproduction with the latter food. A 1:1 mixture (by dry weight) of Euglena gracilis and A. flos-aquae (NRC-44-1) produces survivorship comparable to that of control rotifer cohorts fed E. gracilis alone, but elicits significantly greater fecundity and population growth rates than found with the control food suspension at the same biomass density.     

Pilot study of the Urals population by tooth electron paramagnetic resonance dosimetry

During 1949–1956, about 76 × 10⁶ m³ of radioactive liquid waste containing a total activity of 10¹⁷ Bq was discharged into the Techa River by the first Russian industrial nuclear facility Mayak. As a consequence, the population living in the river valley received considerable internal and external radiation doses. The results of a first application of electron paramagnetic resonance (EPR) of tooth enamel for a retrospective individual dose evaluation of the residents of the Techa riverside are presented. Three main contributions to the dose absorbed in tooth enamel have been considered: external exposure mainly from the Techa River sediments, internal exposure mainly due to ⁹⁰Sr; and background radiation including all other sources of exposure except the Techa River. The teeth of 86 inhabitants of the town Kamensk-Uralskii were analysed to determine the age-dependent contribution of the background radiation to the enamel dose. For 22 residents of the middle and lower Techa riverside, measurements of the ⁹⁰Sr whole-body content and EPR measurements of the absorbed dose in enamel were used to establish a correlation between these two quantities. Finally, absorbed doses in the enamel of five residents of the upper Techa riverside were determined by the EPR method. Contributions of the background radiation and the internal ⁹⁰Sr contamination were subtracted to determine the external exposure of the residents.     

Radiocesium Distribution in Bamboo Shoots after the Fukushima Nuclear Accident

The distribution of radiocesium was examined in bamboo shoots, Phyllostachys pubescens, collected from 10 sites located some 41 to 1140 km from the Fukushima Daiichi nuclear power plant, Japan, in the Spring of 2012, 1 year after the Fukushima nuclear accident. Maximum activity concentrations for radiocesium ¹³⁴Cs and ¹³⁷Cs in the edible bamboo shoot parts, 41 km away from the Fukushima Daiichi plant, were in excess of 15.3 and 21.8 kBq/kg (dry weight basis; 1.34 and 1.92 kBq/kg, fresh weight), respectively. In the radiocesium-contaminated samples, the radiocesium activities were higher in the inner tip parts, including the upper edible parts and the apical culm sheath, than in the hardened culm sheath and underground basal parts. The radiocesium/potassium ratios also tended to be higher in the inner tip parts. The radiocesium activities increased with bamboo shoot length in another bamboo species, Phyllostachys bambusoides, suggesting that radiocesium accumulated in the inner tip parts during growth of the shoots.     

Recombinant and wild-type Pseudomonas aureofaciens strains introduced into soil microcosms: effect on decomposition of cellulose and straw

The effect of a genetically engineered Pseudomonas aureofaciens (Ps3732RNL11) strain (GEM) and the parental wild-type (Ps3732RN) on decomposition of cellulose paper, straw and calico cloth was assessed after 18 weeks incubation in laboratory soil microcosms. Effect(s) of inoculum density (10³, 10⁵, and 10⁸ cells/ g dry soil) and single versus multiple bacterial inoculations were also investigated. Cellulose paper was completely decomposed after 18 weeks in all treatments. There were no significant differences (95% level), between treatments, in percentage decomposition of either straw or calico cloth. Recovery of the GEM at 18 weeks, using viable plating, was limited to treatments originally receiving 10⁸ cells/g dry soil. Log 1.8 CFU/g dry soil were recovered from the single dose treatment while log 4.2 CFU/g dry soil were recovered from the multiple dose treatment Biolog metabolic tests were used to determine if the GEM or parental wild-type had any effect on overall carbon utilization in soil. Results suggested they did not. Detection of the recombinant lacZY gene sequence in soil using PCR suggested the possibility of viable but nonculturable cells and/or persistence of chromosomal DNA.     

Culturable Bacteria in Subglacial Sediments and Ice from Two Southern Hemisphere Glaciers

Viable prokaryotes have been detected in basal sediments beneath the few Northern Hemisphere glaciers that have been sampled for microbial communities. However, parallel studies have not previously been conducted in the Southern Hemisphere, and subglacial environments in general are a new and underexplored niche for microbes. Unfrozen subglacial sediments and overlying glacier ice samples collected aseptically from the Fox Glacier and Franz Josef Glacier in the Southern Alps of New Zealand now have been shown to harbor viable microbial populations. Total direct counts of 2–7 × 10⁶ cells g^–1 dry weight sediment were observed, whereas culturable aerobic heterotrophs ranged from 6–9 × 10⁵ colony-forming units g^–1 dry weight. Viable counts in the glacier ice typically were 3–4 orders of magnitude smaller than in sediment. Nitrate-reducing and ferric iron–reducing bacteria were detected in sediment samples from both glaciers, but were few or below detection limits in the ice samples. Nitrogen-fixing bacteria were detected only in the Fox Glacier sediment. Restriction fragment analysis of 16S rDNA amplified from 37 pure cultures of aerobic heterotrophs capable of growth at 4°C yielded 23 distinct groups, of which 11 were identified as -Proteobacteria. 16S rDNA sequences from representatives of these 11 groups were analyzed phylogenetically and shown to cluster with bacteria such as Polaromonas vacuolata and Rhodoferax antarcticus, or with clones obtained from permanently cold environments. Chemical analysis of sediment and ice samples revealed a dilute environment for microbial life. Nevertheless, both the sediment samples and one ice sample demonstrated substantial aerobic mineralization of ¹⁴C-acetate at 8°C, indicating that sufficient nutrients and viable psychrotolerant microbes were present to support metabolism. Unfrozen subglacial sediments may represent a significant global reservoir of biological activity with the potential to influence glacier meltwater chemistry.     

In vitro selection and characterization of Ni-tolerant callus lines of Setaria italica L

Nickel tolerant callus lines of Setaria italica L. were developed from callus cultures grown on MS medium supplemented with 0.5 mg·dm⁻³ kinetin+2.0 mg·dm⁻³ 2,4-D+2.0 mg·dm⁻³ Ni⁺². Standard growth parameters such as callus fresh and dry weight, growth tolerance index were used as indicators of nickel toxicity. Measurements as early as 2 weeks after the beginning of the treatments did not yield consistent results. However, growth tolerance index at 4, and 8 weeks after the beginning of treatments yielded significant differences among the non-tolerant and tolerant calli. The tolerant calli has enhanced growth at 2.0 mg·dm⁻³ Ni⁺² while non-tolerant calli showed a reverse trend in growth in the presence of 2.0–2.5 mg·dm⁻³ of nickel. The tolerant calli differentiated into mass of embryogenic calli within 4 weeks of culture which could be maintained for prolonged period without loss of regenerative capacity.