Nutrient reserves of Salicornia europaea seeds

Seeds of Salicornia europaea L. were analyzed for their nutrient reserves. The content of potassium and sodium was 216 and 39 mmol (kg dry seeds)^-1, respectively. Calcium and magnesium accounted for 30 and 138 mmol (kg dry seeds)^-1, respectively. Whereas most of the alkali metals were water soluble, the alkaline earth metals were mostly acid soluble. The acid-soluble calcium plus magnesium corresponded well with the acid-soluble phosphate. Chloride was accumulated to a level equivalent to that of sodium. Carbonate was present at a concentration of 9 mmol (kg dry seeds)^-1. Carbohydrates accounted for 93 g (kg dry seeds)^-1, nearly half of which was derived from sucrose. Fructose and glucose were present only in traces. Total nitrogen was determined to be 55 g (kg dry seeds)^-1, 16% of which was diethylether soluble. The remaining nitrogen was separated into 39 g (kg dry seeds)^-1 ethanol-insoluble and 8 g (kg dry seeds)^-1 ethanol-soluble nitrogen. About 10% of the ethanol-soluble nitrogen were derived from amino acids. Total lipid content was about 280 g (kg dry seeds)^-1. The alcoholic component of the storage lipids was glycerol and the glycerides were calculated from gas chromatography to be 66% of the total lipids. About 90% of the fatty acids consisted of unsaturated acids, linoleic and oleic acid, the majority (77%) of which was linoleic acid.     

Some effects of low pH and calcium on the growth and tissue mineral content of yearling brown trout, Salmo trutta

Yearling brown trout, Salmo trutta , were exposed to low mineral content water (nominal concentrations of 20μmol 1⁻¹ magnesium, 7.7 μmol 1⁻¹ potassium, 44 μmol 1⁻¹ sodium) over a pH range of 4.0–5.2 with ambient calcium concentrations of 2.5–60 μmol 1⁻¹. All fish died at pH 4.0 and 4.2 irrespective of ambient calcium concentration and also at pH 4.4 with only 2–3 μmol 1 ⁻¹ calcium (that is calcium-free water except for that leached from the diet or excreted by the fish). Good growth rates were obtained over the remaining treatments which extended down to pH 4.4 with as little as 7 μmol 1⁻¹ calcium. When starved, weight loss was inversely correlated with pH. Effects on plasma chloride, percentage dry weight and calcium, potassium sodium, and phosphorus contents of skin, muscle and bone tissue were also investigated. These demonstrated pH effects on mineral metabolism in starved fish, but no effects were detected in fed fish.     

Growth, mineral uptake and skeletal calcium deposition in brown trout, Salmo trutta L., yolk-sac fry exposed to aluminium and manganese in soft acid water

In 30-day exposures in artificial soft water medium, survival of brown trout alevins was not affected by low pH (4.5,4.8, 5.4), by low calcium concentration (10.25 μmol l⁻¹) or by manganese (≤20 μmol l⁻¹), but was impaired by aluminium (6–8 μmol l⁻¹) at low calcium concentration (10 μmol l⁻¹) irrespective of pH (4.5 or 5.4). Manganese (6.6, 20 μmol l⁻¹) impaired net calcium uptake and calcium deposition in the skeleton at low calcium concentration (25 μmol l⁻¹) irrespective of pH. Aluminium (2–8 μmol l⁻¹) impaired gross development, net uptake of calcium, potassium and sodium, and calcium deposition in the skeleton, and slightly increased the net loss of magnesium, some of these effects being more severe at calcium concentration 10 μmol l⁻¹ than 50 μmol l⁻¹, and some more severe at pH 5.4 than pH 4.5. Net uptake of calcium and sodium were impaired at low pH (4.5, 4.8), and skeletal calcium deposition was impaired at low calcium concentration (10 μmol l⁻¹), but these effects of low pH and low calcium concentration were slight compared with those of the trace metals. The possible role of trace metals in reports of the deleterious effects on fish of low pH levels is discussed.     

Nutritional estimate of populations of some wild free-ranging African ungulates in grassland (Nechisar national park, Ethiopia) in dry season

The amount and nutritive value of forage plants, diet composition, digestibility of dry matter and nutrients were recorded for zebra. Grant's gazelle, Swayne's hartebeest and hippopotamus in November-December 1991 Besides, daily egest of feces, the level of food and nutrient consumption, energy and protein requirements were recorded for zebra and Grant's gazelle The digestibility of pasture forage was determined as a ratio of lignin concentration in food to the concentration m feces (lignin tracer technique), a daily intake was calculated on the basis of the daily feces egest Protein percentage m the diet of zebra and hartebeest consuming dry parts of grasses did not exceed 5% Gazelle diet consists of green parts of plants and included 18% of protein The digestibility of dry matter in nonruminants (zebra, hippopotamus) was 40-45%, in hartebeest - 50%, in gazelle - 60% Due to the abundance of dry grasses (3 7 ton ha^-1) the daily food consumption of zebra was high - 7 2 kg ind^-1 (dry weight), the metabolizable energy intake (ME) being 51 MJ Adult gazelles consumed 15-25 kg ind^-1 of food and 14-24 MJ of ME The energy requirements of adult males and non-lactating females of zebras and gazelles (48 and 13 MJ respectively) were met, the energy balance berig negative for lactating animals The daily protein requirement was not met in zebra (392-704 g md^-1 vs 134 g ind^-1 of intake) and in lactating gazelles (250 g ind^-1 vs 197 g md^-1) Non-lactating gazelles consume sufficient amount of both energy and protein due to the high feeding selectivity of the species and thanks to the abundance of burnt areas with young green after-grass m the dry period     

Role of benthic insect feces in a Rocky Mountain stream: fecal production and support of consumer growth

The feces of stream insects may be a major component of fine particulate organic matter (FPOM) available to collector organisms. In Mink Creek, Idaho, winter defecation rates for 9 species ranged from 86 mg dry feces (g dry body wt)⁻¹ d⁻¹ (Ephemerella spinifera) to 154 mg g⁻¹ d⁻¹ (Paraleptophlebia heteronea) . Detailed studies of 3 species in summer revealed that rates were much greater than in winter and exhibited high between-individual variation (e.g., 695 ± 184.8 mg (g body wt)⁻¹ d⁻¹ for Baetis tricaudatus ). By combining measured and literature values, it is estimated that the benthic insect community egests approximately 3.4 kg feces m⁻² yr⁻¹. This value lies within the range of FPOM estimated to be derived from degradation of leaf litter input (0.7–9.9 kg m⁻² yr⁻¹, depending upon assimilation efficiency of the organisms).
Short-term winter growth experiments showed that, with two exceptions, collectors fed on fecal detritus will grow as well as on other food resources; relative growth rates depend upon the species. Because fecal detritus is abundant throughout the year, and is treated by many species as a source of food, it could be a major mechanism by which seasonal fluctuation in availability of allochthonous litter input is minimized and homeostasis of structure and function maintained.     

Episodic exposure to acid and aluminium in soft water: survival and recovery of brown trout,Salmo trutta L.

Yolk-sac fry, swim-up fry and 1–2 yr juveniles of brown trout, Sulmo trutta L., were exposed to episodes of aluminium and low pH, maximum aluminium concentration 12 μmol l⁻¹ (323 μg l⁻¹), minimum pH 4.5, total duration up to 54 h (yolk-sac fry) or up to 78 h (swim-up fry and juveniles), in an artificial soft water medium, [Ca] 20 μmol l⁻¹ (0–8 mg l⁻¹) (nominal baseline: pH 5.6, zero aluminium concentration). Yolk-sac fry mortality was nil or very low. A marked increase in susceptibility, with high mortalities, occurred when the yolk was fully absorbed. Mortality of juveniles exposed to two successive episodes was lower than would have been expected on the basis of comparisons with mortalities in single episodes, and mortality declined as the interval between the two episodes was increased. Disturbance of sodium, potassium or calcium balance or gill damage in surviving yolk-sac fry or juveniles was still evident 5 to 6 days after the end of a single episode.     

The effect of increased deposition of atmospheric nitrogen on Calluna vulgaris in upland Britain

Regular (monthly) additions of NH₄NO₃ (4–12 g N m⁻² yr⁻¹) were made over a period of 8 yr (1989–98) to areas of moorland in North Wales dominated by the ericaceous shrub Calluna vulgaris . Results from the early stages of the experiment (1990–94) have shown marked and dose-related increases in shoot extension and canopy height in response to the nitrogen treatments, with significantly higher shoot nitrogen contents. The nitrogen-related stimulation in the growth of the C. vulgaris canopy over this period has resulted in large accumulations of litter on the high-nitrogen-treated plots (6.6 kg m⁻² in plots treated with 12 g N m⁻² yr⁻¹, compared with 3.8 kg m⁻² for the water controls). Litter nitrogen concentrations were also significantly increased at the higher rates of nitrogen addition, leading to a doubling of the total return of nitrogen to the litter layer over the experimental period. These changes in vegetation structure were associated with large reductions in the abundance of the bryophyte and lichen species normally present under the untreated canopy. Results since 1994, however, show little increase in shoot extension in response to the nitrogen treatments, with no clear dose response to increasing levels of addition. These findings are associated with a dose-related increase in the susceptibility of the nitrogen-treated areas of the C. vulgaris canopy to late winter injury, characterized as browning of the shoot tips in early to late spring. These results indicate that deleterious effects are now accumulating as a result of the long-term addition of nitrogen to these moorland plots.     

外源施钙对盐胁迫下花生营养元素吸收与分配的影响

为解决盐碱地花生养分吸收不畅及分配受阻等问题,研究外源施钙对盐胁迫下花生氮、磷、钾、钙、镁吸收积累、分配特性和产量的影响,为盐碱地花生生产合理、高效施肥提供理论依据.以‘花育25号’为材料,在0.3%盐胁迫浓度下,设置4个Ca浓度梯度[T₁(0)、T₂(75)、T₃(150)和T₄(225) kg·hm^-2 CaO]进行盆栽试验.结果表明: 花生植株内养分含量依次为氮>钾>钙>磷>镁,苗期植株对氮和钙素的吸收中心均在叶片,磷、钾、镁的吸收中心为茎,苗期近一半的营养积累分配在各元素相应的生长中心.成熟期氮、磷、钾吸收中心转移到荚果中,尤以氮、磷在籽仁中的积累量居多,达72.3%～78.9%;钙、镁的吸收中心仍为叶片和茎,其分配比例分别为49.8%、32.6%.盐胁迫明显抑制花生植株各器官对氮、磷、钾、钙和镁各元素的吸收积累与分配,尤以对叶片和籽仁中氮素积累的抑制较为显著,但盐胁迫对荚果中镁的积累有促进作用.外源钙对盐胁迫下花生植株各器官氮、磷、钙和镁的吸收累积有明显的促进作用,尤其对籽仁中磷素积累的调节最为显著,其在籽仁中的积累量提高50%以上.适宜的钙施用量可显著促进盐胁迫下花生养分吸收积累量,提高花生成熟期荚果中氮、磷、钾的分配比,最终提高产量.综合各养分吸收、积累分配和产量结果,在0.3%盐胁迫条件下钙肥适宜施用量为150 kg·hm^-2 CaO.     

Estimation of the starvation losses of nitrogen and energy in the rainbow trout (Oncorhynchus mykiss) with special regard to protein and energy maintenance requirements

Literature data are analysed regarding losses of body substances occurring during a period of food deprivation in rainbow trout ( Oncorhynchus mykiss ). Nitrogen (protein) and energy losses show a distinct dependence on fish mass (FM [g]) and water temperature (T [°C]). Several regression models for this relationship were compared with best testing estimates as follows:
Nitrogen loss [mg N 2 fish⁻¹ 2 d⁻¹] = 0.0658 e^(1.037) 2 FM^0.739
( n = 49, 9–20°C, 5–400g fish mass, P < 0.001, B = 0.826)
Nitrogen-corrected energy loss [J 2 fish⁻¹ 2 d⁻¹] = 22.09 e^(1.034) 2 FM^0.833
( n = 63, 9–25°C, 8–400 g fish mass, P < 0.001, B = 0.887).
For nitrogen loss as well as for nitrogen-corrected energy loss, the metabolic rate shows a progressive increase with rising water temperature. The temperature coefficient increases in magnitude as temperature increases. The introduction of a general common exponent (0.8 instead of 0.739 for nitrogen loss and 0.833 for energy loss) for fish mass decreases the precision of the estimate. The equations could serve as a base for estimating net protein and net energy maintenance requirements of rainbow trout. Possible limitations, caused by uncertainities in estimating the elevated metabolic rate by food intake and ingestion, are discussed.     

Energy and ration requirements of juvenile Pacific halibut (Hippoglossus stenolepis) based on energy consumption and growth rates

Growth of captive juvenile Pacific halibut was linearly related to energy consumption (J g⁻¹ day⁻¹) at 4°C by the following equation: growth (% body weight (b.w.) day⁻¹)=0–007 (consumption J g⁻¹ day⁻¹)– 0.192; r² =0.81. Weight gain was independent of size for fish between 9 and 7000 g when growth was expressed as a function of consumption in J g⁻¹ day⁻¹. Maintenance ration determined in feeding–growth experiments averaged 27.4 J g⁻¹ day⁻¹ at 4–0°C. Small halibut ate significantly more food than large fish. Single meals following 2 day fasts averaged 4.1% b.w. for halibut under 100 g, 1.72% b.w. for 1.2 kg fish and 1.1% B.W. for 6.8 kg fish. Both large and small size categories of halibut tended to evacuate their meal in about 3 days even though small fish ate relatively larger meals. Minimum estimates for daily ration to achieve growth rates observed in the Gulf of Alaska were approximately 0.5 to 2.4% b.w. day⁻¹ depending on fish size and whether northern shrimp or yellowfin sole were their prey.     

A potential anti-oxidant protein in a ferrous iron-oxidizing Sulfolobus species

Abstract Eight species of halophilic Archaea were tested for the presence of isocitrate lyase activity. High activities (up to 100 nmol min⁻¹ mg protein⁻¹) were detected in Haloferax mediterranei and Haloferax volcanii when grown in medium containing acetate as the principal carbon source. Little activity was found in representatives of the genera Halobacterium and Haloarcula . Isocitrate lyase from Haloferax mediterranei required high potassium chloride concentrations, optimal activity being found at 1.5–3 M potassium chloride and pH 7.0. Replacement of potassium chloride by sodium chloride resulted in much lower activities. Sulfhydryl compounds (cysteine, glutathione) were not stimulatory. In other properties (stimulation by magnesium ions, sensitivity to different inhibitors) the enzyme resembled isocitrate lyases from representatives of the Bacteria and Eucarya.     

Changes in forest soils and vegetation in Søgne, southern Norway, during a 20 year period

An investigation of the edaphic conditions and the vegetation of 21 fixed plots in Søgne municipality, Vest-Agder, South Norway was carried out in 1967-69 and 1987. Loss on ignition, pH, total nitrogen, total exchangeable bases, base saturation, exchangeable hydrogen, sodium, potassium, magnesium, calcium and manganese was analysed. The species composition of vascular plants was investigated. The total cover of the bottom layer was scored.
The soil pH had decreased in the more basic soils but had increased in the more acidic soils. The organic content had increased and base saturation had decreased in most samples. Na⁺ had increased in more than half of the plots, Ca²⁺ and Mg²⁺ had not changed, and K⁺ and Mn²⁺ had decreased in most plots. Salt depositions from the neighbouring North Sea and leaching from the soil accounted for these changes. In many of the parameters opposite changes were found in the poorer soils compared to the richer soils. In the field layer Deschampsia flexuosa, Convallaria majalis had increased, and Oxalis acetocella, Galium odoratum had decreased. The cover of cryptogams had decreased in most of the plots.     

Isolation of an inclusion body from sporulating, enterotoxin-positive Clostridium perfringens

Abstract Inclusion bodies (IB) synthesized during sporulation and enterotoxin formation by Clostridium perfringens were isolated. Sporulating cells were lysed by sonication in the presence of protease inhibitors. IB were isolated by centrifugation in linear gradients of sucrose, sodium bromide or sodium diatrizoate and banded at buoyant densities of 1.33–1.36 g/cm³, 1.30–1.34 g/cm³ and 1.33 g/cm³, respectively. Isolated IB were treated with detergent to remove attached cell membrane. They ranged in size from 0.5–1.4 μm long and from 0.2–0.5 μm wide. They were found to be serologically related to purified enterotoxin.     

Calcium and magnesium effects on symbiotic nitrogen fixation in the alfalfa (M. sativa) –Rhizobium meliloti system

An investigation of the roles of calcium and magnesium ions in symbiotic nitrogen fixation by legumes has shown that alfalfa plants ( Medicago sativa L. cv. Saranac and Apollo) deficient in either cation were poorly nodulated and retarded in growth on nitrogen-free media. This effect was reversed by supplementation with normal levels of these cations. After recovery, the calcium deficient seedlings showed continuing effects of early mineral deficiencies but recovered to 75% of the nitrogenase activity and had nearly the same yield as control plants. Magnesium deficient plants recovered nitrogenase activity to the same degree but grew to only about 50% of the weight of controls. Supplementation of non-deficient seedlings grown on N-free media with varying amounts of Ca²⁺ and Mg²⁺ resulted in the identification of an optimal ratio of calcium and magnesium near 2 when neither cation was growth limiting. A highly significant positive correlation was obtained between yield of dry matter and the fraction of total expressed nitrogenase activity that was actually available for dinitrogen reduction (nitrogen reducing equivalent). Bacteroids isolated from root nodules and freed of plant cytoplasmic components required high magnesium levels for maximal utilization of externally supplied ATP and dithionite. Ca⁺ was antagonistic to this activity but complemented Mg²⁺ in stimulating the respiration-supported nitrogenase activity of intact bacteroids which had been treated with a chelating agent. The effects of calcium and magnesium on the nitrogenase system of intact bacteroids may be due to binding of the Ca²⁺ ions to the bacteroid membrane.     

Bioenergetics of growth of a cyprinid, Phoxinus phoxinus: the effect of ration, temperature and body size on food consumption, faecal production and nitrogenous excretion

Food consumption, faecal production and nitrogen excretion by minnows, Phoxinus phoxinus , weighing 1–5.5 g were studied at five rations ranging from starvation to ad libitum and four temperatures ranging from 5 to 15°C.
The maximum rate of food consumption (C_max) was related to body weight ( W ) and temperature ( T ) by the relationship: C _max= aW^b1T^b2 . There were significant daily variations in C_max, which tended to decline over time. Absorption efficiency increased with increasing ration size and decreasing temperature. Body weight had no significant effect on the faecal production. The equation F = a C^b1e^b2 T described the relationship between faecal production ( F ), food consumption ( C ) and temperature. Ammonia-N predominated over urea-N in the excreta of most experimental fish. The proportion of urea-N in the total nitrogen excreted was generally higher at lower rations than at higher rations. Rates of nitrogen excretion increased with increased ration size and were, to a lesser extent, influenced by temperature. Body weight had no significant effect on the nitrogen excretion by feeding minnows. The equation N = a+b_lT+b₂C described the effects of food consumption and temperature on nitrogen excretion ( N ) other than urea-N excretion. The relationship between urea-N excretion ( N_u ), food consumption and temperature was described by the equation N_u= ae^b1T ((C+1) ^b 2.
On the average, 11 % of food energy was lost in faecal production and nitrogen excretion by minnows feeding on whiteworms, Enchytraeus spp.     

Kinetic and metabolic effects of nitrogen, magnesium and sulphur restriction in Xanthomonas campestris batch cultures

By reducing the concentration of nitrogen (from 5.0 to 2.5 mmol 1^-1), batch cultures of Xanthomonas campestris induced the enzyme UDP-glucose dehydrogenase and stimulated the Entner-Doudoroff pathway enzyme glucose-6-P dehydrogenase. The surplus energy generation was directed to xanthan biosynthesis resulting in a 10% polysaccharide increase. The nitrogen restriction led to a higher consumption of nitrogen (93%) whereas glucose consumption did not surpass 75% utilization. Low concentrations of both magnesium and sulphur exerted a negative effect on xanthan formation. Both restrictions reduced the phosphomannose isomerase enzyme activity by 10-fold turning the mannose transference presumably into the rate-limiting step for xanthan biosynthesis. Conversely, the rate of synthesis of glucuronic acid residues did not affect the rate of xanthan biosynthesis. Polysaccharide synthesis in magnesium and sulphur cultures was negatively affected in comparison with cell formation as the cell volumetric production rate increased from 0.037 to 0.091 g 1^-1 h^-1 and the xanthan volumetric production rate dropped from 0.133 g 1^-1 h^-1 to the minimum obtained at 0.083 g 1^-1 h^-1. The efficiency of the carbon substrate conversion was also greatly changed.     

The relative abundance of brown trout in acidic softwater lakes in relation to water quality in tributary streams

The influence of the water quality of tributary streams on the relative abundance in benthic gillnet catches (catch per unit effort, cpue) of allopatric brown Salmo trutta was assessed in associated acidic, softwater lakes. The study was carried out over 6 years (1989–1994) in 15 lakes located at altitudes between 230–715 m a.s.l. in two Norwegian catchments. The water quality of the main inlets and outlets varied little, as indicated by their of pH range (4·93–5·51) and calcium concentrations (0·19–0·44 mg 1⁻¹), but varied more with respect to concentrations of inorganic, monomeric aluminium (7·0–41·0 μg l⁻¹). Most of the lakes were also fed by secondary streams with better water quality: a maximum pH of 6·56, calcium levels of up to 0·74mg 1⁻¹, and inorganic aluminium levels as low as l·0 μg 1⁻¹. The cpue was inversely correlated with lake altitude ( r ²=0·50), and thus was adjusted to a mean altitude. The calcium concentration in the richest secondary stream to each lake, its richness judged on the basis of its acid-neutralizing capacity, had the highest predictive power of the variability in cpue ( r ² = 0·49).The calcium content in the other secondary streams or in the main inlets and outlets did not correlate with cpue. Alkalinity in the main outlets correlated to some extent with cpue ( r ² = 0·27). It is suggested that secondary streams with good water quality provide important refuges for the recruitment of brown trout in acidic softwater lakes.     

Effect of ion channel blockers on germination of Bacillus megaterium spores

Abstract We surveyed 23 drugs that can interact with membrane components, such as ion channels, for their effect on spore germination. The results showed that triggering of spore germination was inhibited by specific calcium (Ca²⁺) potassium (K⁺) and sodium (Na⁺) channel blockers.     

Planktic cyanophytes and their ecology in the shallow Lake Mikri Prespa, Greece

Cyanophytes dominated the phytoplankton of shallow Lake Mikri Prespa during the period May 1990 to September 1992 (76.5 and 52.0% of the total phytoplankton biomass in 1990–1991 and 1991–1992, respectively). Biomass peaks were observed in autumn (from 5.2 to 34.5 g m^-3) when low dissolved inorganic nitrogen, high phosphate phosphorus and low Z_cu to Z_mix ratio prevailed. The dominant species were Microcystis aeruginosa and M. wesenbergii. These represented 64 and 86% of the cyanophyte biomass in 1990–1991 and 1991–1992, respectively and revealed similar patterns of seasonality forming biomass peaks in late summer - autumn. Small chroococcalean cyanophytes (< 2 μm) showed also similar temporal distributions. Of the filamentous cyanophytes, the most important species was Anabaena lemmermannii var. minor which formed peaks in late summer and autumn (2.6 and 1.1 g m^-3 in 1990 and 1992, respectively). Rainfall and the N:P ratio were probably the main factors influencing the seasonality of all of the filamentous cyanophytes in the lake. Cyanophytes, tended to increase at temperatures higher than 16 °C and at inorganic nitrogen concentrations lower than 100 μg 1^--¹. The frequent mixing of the water column did not seem to prohibit the substantial increase of the group.     

Sublittoral abundance and food consumption of Baltic gobies

Two small demersal fishes, the sand goby Pomatoschistus minutus and the common goby Pomatoschistus microps , were quantified on soft bottoms at 20–40 m depth in the Baltic Sea, using a camera placed above the bottom. The largest numbers of gobies were seen following the settlement of young in late summer and autumn. Most recorded fishes were sand gobies. An annual average of 4·7 individuals m⁻²(0·24 g dry mass m⁻²) was recorded in 1983–1985 and 2·5 individuals m⁻²(0·13 g m⁻²) in 1997–1998. Using these densities, the annual goby food consumption was estimated to 100 kJ m⁻² in 1983–1985 and 50 kJ m⁻² in 1997–1998, corresponding to most of the annual macrobenthos production available to the gobies. The resulting goby production, assumed equal to 25% of the food consumed, must have been an important food source for the larger fishes occasionally recorded in the photographs.