Showing papers by "Swedish University of Agricultural Sciences published in 1993"

The abundance of various polymorphic microsatellite motifs differs between plants and vertebrates

Abstract: The abundance of different simple sequence motifs in plants was accessed through data base searches of DNA sequences and quantitative hybridization with synthetic dinucleotide repeats. Database searches indicated that microsatellites are five times less abundant in the genomes of plants than in mammals. The most common plant repeat motif was AA/TT followed by AT/TA and CT/GA. This group comprised about 75% of all microsatellites with a length of more than 6 repeats. The GT/CA motif being the most abundant dinucleotide repeat in mammals was found to be considerably less frequent in plants. To address the question if plant simple repeat sequences are variable as in mammals, (GT)n and (CT)n microsatellites were isolated from B.napus. Five loci were investigated by PCR-analysis and amplified products were obtained for all microsatellites from B. oleracea, B.napus and B.rapa DNA, but only for one primer pair from B.nigra. Polymorphism was detected for all microsatellites.

Litter mass loss rates in pine forests of Europe and Eastern United States: some relationships with climate and litter quality

Abstract: The purpose of this study was to relate regional variation in litter mass-loss rates (first year) in pine forests to climate across a large, continental-scale area The variation in mass-loss rate was analyzed using 39 experimental sites spanning climatic regions from the subarctic to subtropical and Mediterranean: the latitudinal gradient ranged from 31 °N to 70 °N and may represent the the largest geographical area that has ever been sampled and observed for the purpose of studying biogeochemical processes Because of unified site design and uniform laboratory procedures, data from all sites were directly comparable and permitted a determination of the relative influence of climateversus substrate quality viewed from the perspective of broad regional scales Simple correlation applied to the entire data set indicated that annual actual evapotranspiration (AET) should be the leading climatic constraint on mass-loss rates (Radj 2 = 0496) The combination of AET, average July temp and average annual temp could explain about 70% of the sites' variability on litter mass-loss In an analysis of 23 Scots pine sites north of the Alps and Carpatians AET alone could account for about 65% of the variation and the addition of a substrate-quality variable was sufficiently significant to be used in a model The influence of litter quality was introduced into a model, using data from 11 sites at which litter of different quality had been incubated These sites are found in Germany, the Netherlands, Sweden and Finland At any one site most ( ≫ 90%) of the variation in mass-loss rates could be explained by one of the litter-quality variables giving concentration of nitrogen, phosphorus or water solubles However, even when these models included nitrogen or phosphorus even small changes in potential evapotranspiration resulted in large changes in early-phase decay rates Further regional subdivision of the data set, resulted in a range of strength in the relationship between loss rate and climatic variables, from very weak in Central Europe to strong for the Scandinavian and Atlantic coast sites (Radj 2 = 0912; AETversus litter mass loss) Much of the variation in observed loss rates could be related to continentalversus marine/Atlantic influences Inland locations had mass-loss rates lower than should be expected on the basis of for example AET alone Attempts to include seasonality variables were not successful It is clear that either unknown errors and biases, or, unknown variables are causing these regional differences in response to climatic variables Nevertheless these results show the powerful influence of climate as a control of the broad-scale geography of mass-loss rates and substrate quality at the stand level Some of these relationships between mass-loss rate and climatic variables are among the highest ever reported, probably because of the care taken to select uniform sites and experimental methods This suggest that superior, base line maps of predicted mass-loss rates could be produced using climatic data These models should be useful to predict the changing equilibrium litter dynamics resulting from climatic change

A small diffusible signal molecule is responsible for the global control of virulence and exoenzyme production in the plant pathogen Erwinia carotovora.

Abstract: Virulence of the plant pathogen Erwinia carotovora subsp carotovora is dependent on the production and secretion of a complex arsenal of plant cell wall-degrading enzymes Production of these exoenzymes is controlled by a global regulatory mechanism A virulent mutants in one of the regulatory loci, expI, show a pleiotropic defect in the growth phase-dependent transcriptional activation of exoenzyme gene expression The expI gene encodes a 26 kDa polypeptide that is structurally and functionally related to the luxI gene product of Vibrio fischeri Functional similarity of expI and luxI has been demonstrated by reciprocal genetic complementation experiments LuxI controls bioluminescence in Vfischeri in a growth phase-dependent manner by directing the synthesis of the diffusible autoinducer, N-(3-oxohexanoyl) homoserine lactone Ec subsp carotovora expI+ strains or Escherichia coli harboring the cloned expI gene excrete a small diffusible signal molecule that complements the expI mutation of Erwinia as well as a luxI mutation of Vfischeri This extracellular complementation can also be achieved by Ecoli harboring the luxI gene from Vfischeri or by adding the synthetic Vfischeri autoinducer Both the production of the plant tissue-macerating exoenzymes and the ability of the bacteria to propagate in planta are restored in expI mutants by autoinducer addition These data suggest that the same signal molecule is employed in control of such diverse processes as virulence in a plant pathogen and bioluminescence in a marine bacterium, and may represent a general mechanism by which bacteria modulate gene expression in response to changing environmental conditions

Differential expression of two related, low-temperature-induced genes in Arabidopsis thaliana (L.) Heynh.

Abstract: Plant cold acclimation is correlated to expression of low-temperature-induced (lti) genes. By using a previously characterized lti cDNA clone as a probe we isolated a genomic fragment that carried two closely located lti genes of Arabidopsis thaliana. The genes were structurally related with the coding regions interrupted by three similarly located short introns and were transcribed in the same direction. The nucleotide sequences of the two genes, lti78 and lti65, predict novel hydrophilic polypeptides with molecular weights of 77856 and 64510, respectively, lti78 corresponding to the cDNA probe. Of the 710 amino acids of LTI78 and 600 amino acids of LTI65, 346 amino acids were identical between the polypeptides, which suggests that the genes may have a common origin.

Relationship between N immobilization and volatile fatty acids in soil after application of pig and cattle slurry

Abstract: A laboratory study was performed to determine decomposition of fatty acids and mineralization of C and N from slurries in soil. Fatty acids present in slurries decomposed within 1–2 days at 25°C in soil. Parallel to the fatty acid decomposition, immobilization of N was measured in soil. The correlation between the initial fatty acid concentrations in the slurries and the amounts of N immobilized were found to be highly significant (R 2=0.97). It was concluded that fatty acids act as an easily decomposable C source for microorganisms and cause immobilization of N. Immobilization of N was followed by a curvilinear mineralization of N in all slurrytreated soils. Despite mineralization, only fresh pig slurry and anaerobically digested pig slurry showed a net release of N over 70 days whereas cattle slurry and anaerobically fermented pig slurry did not. The percentage of slurry C evolved during 70 days was fresh pig slurry, 65%; anaerobically fermented pig slurry, 48%; anaerobically digested pig slurry, 45%; and anaerobically fermented cattle slurry, 42%.

Structure and regeneration patterns in a virgin Picea abies forest in northern Sweden.

Abstract: . A high-altitude boreal Picea abies forest, with tree ages of up to 410 yr, was studied with respect to age structure, spatial regeneration patterns, and substrate. The results suggest that recruitment is primarily dependent on germination substrate but also negatively correlated with the density of the tree layer. 60 % of all spruces < 1.3 m high grew on substrates connected with tree-fall; ca. 40 % were found on decomposing logs and stumps, covering only ca. 6 % of the forest floor. Individual logs remain important as a regeneration substrate for ca. 150 yr. Continuous presence of decomposing coarse wood is a condition for the maintenance of the population structure under the prevailing climatic conditions. Peaks in the age distribution (the 1870's and the 1940's - 1950's) are probably climatically induced. The results challenge the previous assumptions that this kind of forest undergoes cyclic development. Long-term structural stability with climatically induced minor variations may be an alternative model.

Temporal variation in the hydraulic conductivity of a tilled clay soil as measured by tension infiltrometers

Abstract: SUMMARY Steady-state infiltration rates from tension infiltrometers were measured on ploughed and unploughed plots in a clay soil during the period June to October Measurements were made both at the soil surface and at depths of 15 and 25 cm Hydraulic conductivity in the water potential range zero to −11 cm was obtained using a piece-wise exponential K(Ψ) function and Wooding's solution for infiltration from a circular source A two-line regression model showed excellent fits to paired (In KΨ) values on all measurement occasions This may indicate the existence of a bimodal pore system, reflecting the contributions of macro- and mesopores to the measured K(Ψ) function The break-point potential dividing the two pore systems varied between c−4 and −6cm Significant variations in the K(Ψ) function between sampling occasions were found at the soil surface, but not at depths of 15 and 25 cm Measured K(Ψ) values decreased during the growing season, particularly at potentials between −4 and −6 cm where reductions were up to one order of magnitude This was attributed to soil structural breakdown by rain impact and surface capping or sealing Hydraulic conductivity near the soil surface was significantly increased by disc harrowing in autumn In contrast, no pronounced difference in the K(Ψ) function between ploughed and unploughed treatments could be discerned at 15 and 25 cm depths in the soil

Muscle histochemical and biochemical properties in relation to meat quality during selection for increased lean tissue growth rate in pigs.

Abstract: The relationship between the histochemical and biochemical properties of muscle and the quality of meat during selection to improving the lean tissue growth rate was studied. Pigs (n = 82) from Generations 2 and 4 were randomly sampled in a selection experiment in which the genotype x protein interaction was studied. Comparisons were made of longissimus muscle (LM) and quadriceps femoris (QF) from Generations 2 and 4, and biceps femoris (BF) in the fourth generation from pigs fed a low- or high-protein diet. A higher total growth rate, lean tissue growth rate, and lean percentage were found in pigs fed the high-protein diet than in pigs fed the low-protein diet. Pigs fed the high-protein diet had a higher glycolytic capacity in all muscles than pigs fed the low-protein diet. When the meat quality traits were compared, pigs fed the high-protein diet had a lower intramuscular fat content, higher shear force value, higher protein extractability, lower light reflectance, and somewhat higher water-holding capacity. With selection, pigs became fatter on both diets. In Generation 4, glycolytic and oxidative capacity was somewhat higher in muscle tissue than in Generation 2. Muscle metabolic profile and meat quality traits differed among muscles (LM, BF, QF) but no pronounced differences were found between generations. No marked changes were observed in Type I, IIA, or IIB fibers, either between diets or between generations. The Type IIC fibers could only be identified in Generation 4.

Prognostic Factors in Canine Mammary Tumors: A Multivariate Study of 202 Consecutive Cases

Abstract: The prognostic variables of 223 consecutively sampled spontaneous mammary tumors from female dogs were studied. These variables included flow cytometric DNA analysis and cell proliferation measured as cells in S-phase rate evaluated from DNA histograms. The dogs were surgically treated, in most cases with unilateral mastectomy (all mammary glands), and 202 of the 223 dogs were studied temporally following surgery. Univariate analysis with correction for age indicated that the variables of lymph node metastasis, elevated S-phase rate, presence of a sarcoma, DNA aneuploidy, and ulceration and infiltrative growth into underlying tissue had a statistically significant negative influence on the survival rates of dogs with a diagnosed malignant tumor. Similar results were obtained from tests on all dogs, but tumor size and its relative hazard increased with increasing size of the tumors, regardless of whether total or disease-specific mortality was considered. Using multivariate-analysis conducted Cox's proportional hazards model, elevated S-phase rate, increased age, and presence of a sarcoma remained statistically significant risk factors. The prognostic value of DNA ploidy and lymph node status varied depending on choice of end point. The study of tumor growth pattern and tumor size provided no prognostic information in the multivariate analysis. Flow cytometric cell analysis, including S-phase rate and DNA ploidy, is of value in predicting the prognosis of canine mammary tumors and can be used as a new prognostic tool to improve the preoperative diagnostics of canine mammary tumors.

Major histocompatibility complex monomorphism and low levels of DNA fingerprinting variability in a reintroduced and rapidly expanding population of beavers

Abstract: Loss of genetic variation due to population bottlenecks may be a severe threat for the survival of endangered species. Assessment and maintenance of genetic variability are thus crucial for conservation programs related to endangered populations. Scandinavian beavers went through an extensive bottleneck during the last century due to overhunting. In Sweden the species became extirpated but in Norway extinction was avoided by legal protection. Following reintroductions of small numbers of remaining Norwegian animals in 1922-1939, the Swedish population has increased tremendously, now harboring 100,000 animals. We show here that this viable population of beavers possesses extremely low levels of genetic variability at DNA fingerprinting loci and monomorphism at major histocompatibility complex (MHC) class I and class II loci. A similar pattern was also evident among Norwegian beavers but low levels of genetic variability were not a characteristic of the species since Russian conspecifics displayed substantial DNA fingerprinting polymorphism. However, the Russian animals were monomorphic at MHC loci, indicating that the European beaver is exceptional in its low level of MHC variability. The results demonstrate that a conservation program can be successful despite low levels of genetic variation in the founder population.

Soil Solution Chemistry: Effects of Bulking Soil Samples

Abstract: Bulking of soil samples is commonly used to obtain a spatially averaged measure of soil properties. This study investigated whether bulking can affect the chemistry of soil solution extracted by the centrifuge drainage technique. The short-range variation within a 1-m-wide pit face was also investigated. Systematic differences were found between the chemistry of soil solutions taken from bulked and unbulked soil samples. The soil samples studied were taken on several occasions from the upper and lower part of a Bs horizon. Samples of soil solution extracted from replicate bulked soil samples contained significantly (P ≤ 0.05) larger amounts of Si, Na, Mg, and K as well as significantly (P ≤ 0.05) smaller amounts of Al and Fe than soil solution from unbulked samples. Bulking reduced the variation in all solutes measured, although a variation remained in replicates from the bulked sample. The variation between individual core samples taken just a few tens of centimeters apart can be considerable, although the magnitude of variation differs depending on the solute studied. The results suggest that unbulked soil samples may be preferable, especially when Al or Fe chemistry is studied and a centrifuge drainage technique is used. Contribution from Swedish Environmental Protection Agency, contract no. Dnr 802-761-91-Fs.

Osteochondrosis in the tarsocrural joint and osteochondral fragments in the fetlock joints in Standardbred trotters. I. Epidemiology

Abstract: Summary Radiographic examinations of the tarsocrural and metacarpo/metatarsophalangeal joints were made in two groups of 1.5-year-old Standardbreds. One group comprised 674 horses drawn at random from the Swedish population of Standardbred trotters to provide an estimate of the incidence of tarsocrural joint osteochondrosis and osteochondral fragments in the fetlock joints. An additional 119 progeny of 4 stallions which themselves had osteochondrosis or fetlock fragments were included for the study of the distribution of lesions and the characteristics of affected animals, i.e. a total of 793 animals. The radiographic views were chosen to detect osteochondrosis in the tarsocrural joints (OC) and palmar/plantar osteochondral fragments (POF), ununited palmar/plantar eminences (UPE) and dorsal fragments (DF) in the fetlock joints. The incidence of tarsocrural joint OC was estimated as 10.5% while palmar/plantar osteochondral fragments in the fetlock joints were present in 21.5% of the 674 animals. In the group of 793 animals, tarsocrural joint OC was seen in 11.5% of the horses and was found bilaterally in 45% of the affected animals. In the fetlock joints, POF was found in 22.4%, UPE in 4.2% and DF in 4.4% of the horses. One or several of the lesions were found in 35.9% of the 793 horses. There were no significant sex differences in the incidence of OC and POF, but when all lesions were considered males were significantly more often affected than females (40.5% vs 31.2%). Of the OC lesions in the tarsocrural joint, 95% were found at the intermediate ridge of the tibia and 5% were seen at the lateral trochlea of the talus. POF and UPE mainly occurred in the hindlimbs. In 75% of the POF cases, the findings were located in the medial part of the joint while UPE findings almost exclusively were found laterally. Horses with UPE had a significantly higher incidence of POF. The incidence of OC in the tarsocrural joint was related to the date of birth and the incidence was higher in the later than in the early part of the foaling season. The incidence of OC findings was also related to body size. Horses affected were taller at the withers and had a greater circumference of the carpus. Synovial effusions of the tarsocrural joint were significantly more pronounced in horses with radiographic signs of OC. In horses with POF and UPE, synovial effusions of the fetlock joints were not more frequent or severe.

Spatial and temporal variation in lightning ignitions in Sweden

Abstract: Analysis of fire statistics revealed that there are steep gradients in the distribution of lightning-caused fire ignitions in Sweden. The highest ignition density was found in the southeastern provinces of Kalmar and Osterg6tland, ca. 0.23/10 000 ha/yr. From there, densities generally declined both to the north and to the west, with a density averaging ca. 0.05 in the six northernmost provinces, and an equally low density in the southwestern province of Halland. For both northern and southern Sweden, lightning ignitions peaked in early July, but in the south the season for ignitions started 2 - 3 weeks earlier and ended 2 - 3 weeks later. The geographical gradients in lightning ignition density correspond to the aver- age precipitation during summer. The patterns of lightning ignition densities may also indicate gradients in natural fire frequencies. This hypothesis is supported by the distribution of certain fire-adapted plant species.

Nosema Apis—A Parasite in the Honey Bee Colony

Abstract: (1993). Nosema Apis—A Parasite in the Honey Bee Colony. Bee World: Vol. 74, No. 1, pp. 5-19.

Size of the soil microbial biomass in a long-term field experiment as affected by different n-fertilizers and organic manures

Abstract: The size of the soil microbial biomass was measured in a more than 30 yr old field experiment, whose treatments included different N fertilizers and organic manures. The size of the microbial biomass was measured as biomass C and N by the chloroform fumigation-incubation technique, as K2SO4 extractable ninhydrin-reactive N released upon fumigation and as the soil's ATP content. There was a high degree of correlation (r > 0.88) between the fumigation-based methods and the ATP determinations. Compared with the biomass estimate by ATP, biomass C was underestimated in the ammonium sulphate fertilized soil (pH 4.4), the peat-amended soils, and the sewage sludge amended soil. Biomass N was only underestimated in the ammonium sulphate and peat-amended soil, whereas there was a good correlation between the ninhydrin assay and the ATP assay for all soils. Between three successive years biomass C showed larger, statistically significant, variations than the size of the biomass measured by the ninhydrin assay. There was a high degree of correlation (r > 0.90) between both the rate of base respiration and the size of the microbial biomass and the soil's carbon content. These relationships generally held independent of whether carbon was derived from stabilized soil organic matter (in the fallow soil), from crop residues, or from organic manures such as straw, green manure, farmyard manure, or sawdust. Relative to the soil's carbon content the microbial biomass was smaller than expected in the peat amended-soils, the ammonium sulphate fertilized, and the sewage sludge-amended soil. The rate of base respiration was only lower than expected in the sewage sludge treated soil. The size of the biomass was negatively affected by a low soil pH, but the rate of base respiration was not. Liming some of the soils indicated that other factors than low pH restricted the size of the biomass in the peat and sewage-sludge amended soils, but not in the ammonium sulphate fertilized soils.

15N Abundance of forests is correlated with losses of nitrogen

Abstract: A direct correlation was found between fractional losses of added N and the change in δ15N‰ during 19 years in an experiment with annual additions of N at three rates to a Scots pine (Pinus sylvestris L.) forest in northern Sweden. This confirms that processes leading to losses of N discriminate against15N, and opens possibilities to conduct retrospective studies of the N balance in forests.

The role of organic acids in the soil solution chemistry of a podzolized soil

Abstract: SUMMARY The soil solution chemistry of a podzolized soil in the north of Sweden was monitored for four years using percolation lysimeters. Weak organic acids were a major constituent of the soil solution and are important because of their ability to form complexes with aluminium. Dissolved organics leached from the mor layer enhance the weathering rate in the eluvial horizon by forming complexes with aluminium, especially during the autumn when the leaching of dissolved organics was greatest. The weak organic acids were titrated and their pKa values were evaluated. Aluminium was speciated with an ion-exchange method and by applying equilibrium calculations. Formation constants for the organic aluminium complexes were calculated to be log KAlong=5.42±0.32 m−1 (n=13) in spring and summer and log KAlorg=4.87±0.14 m−1 (n=6) in autumn. Equilibria of Al3+ with solid phases were also examined using solubility constants. Percolation lysimeters below undisturbed and cut-off mor layers were compared.

Deletion analysis of a 2S seed storage protein promoter of Brassica napus in transgenic tobacco.

Abstract: The promoter and upstream region of the Brassica napus 2S storage protein napA gene were studied to identify cis-acting sequences involved in developmental seed-specific expression. Fragments generated by successive deletions of the 5' control region of the napA gene were fused to the reporter gene beta-glucuronidase (GUS). These constructs were used to transform tobacco leaf discs. Analyses of GUS activities in mature seeds from the transformed plants indicated that there were both negatively and positively acting sequences in the napin gene promoter. Deletion of sequences between -1101 and -309 resulted in increased GUS activity. In contrast, deletion of sequences between -309 and -211 decreased the expression. The minimum sequence required for seed-specific expression was a 196 bp fragment between -152 and +44. Further 5' deletion of the fragment to -126 abolished this activity. Sequence comparison showed that a G box-like sequence and two sequence motifs conserved between 2S storage protein genes are located between -148 to -120. Histochemical and fluorometric analysis of tobacco seeds showed that the spatial and developmental expression pattern was retained in the deletion fragments down to -152. However, the expression in tobacco seeds differed from the spatial and temporal expression in B. napus. In tobacco, the napA promoter directed GUS activity early in the endosperm before any visible activity could be seen in the heart-shaped embryo. Later, during the transition from heart to torpedo stages, the main expression of GUS was localized to the embryo. No significant GUS activity was found in either root or leaf.

Relationship between the levels of antibodies to bovine viral diarrhoea virus in bulk tank milk and the prevalence of cows exposed to the virus

Abstract: A positive relationship was found between the prevalence of cows in a herd which were antibody-positive for bovine viral diarrhoea virus (BVDV) and the level of antibodies to the virus in bulk tank milk as determined by an indirect enzyme-linked immunosorbent assay (ELISA). In herds with an ELISA absorbance value of up to 0.20 there were very few or no antibody-positive cows, whereas in herds with an ELISA absorbance value of at least 0.81, 87 to 100 per cent of the lactating cows were antibody-positive to BVDV. An analysis of the level of antibodies to BVDV in milk samples from Sweden and Finland showed that of 123 Swedish herds, 83.7 per cent had detectable antibodies to BVDV in their bulk milk whereas only 3.1 per cent of the 291 Finnish samples were antibody-positive. The incidence of BVDV infection in 105 herds in one area of Sweden was determined by analysing two samples of bulk tank milk taken one year apart. The infection had apparently occurred recently in five of these dairy herds.

Naive birds and noble savages - a review of man-caused prehistoric extinctions of island birds

Abstract: Many bird species were extirpated or became extinct when prehistoric man reached oceanic islands We list > 200 species of extinct island birds only recorded as sub-fossils and which probably vanished due to prehistoric man In addition we list c 160 cases where an extant species has been found as subfossil on islands where it no longer occurs Several species today considered endemic to single islands of island groups had a much wider distribution in the past Biogeographic analyses of insular avifaunas are almost meaningless it the extensive prehistoric extinctions are not taken into account Most extinct species belong to Anatidae Rallidae and Drcpanididae while local extirpations are numerous among doves and seabirds Smaller birds are rare mainly due to sampling bias and taphonomic factors The bird populations were depleted mainly by overhunting predation by introduced vertebrates and alteration of the original vegetation Prehistoric humans on islands although dependent on limited animal resources regularly failed to exploit these in a sustainable way Several cases where human populations disappeared from islands in the Pacific may have been due to over-exploitation of native animals Prehistoric man reached most tropical and temperate islands and most of the few remaining island faunas have been severely depleted in historic times The prehistoric extinctions emphasize the extreme vulnerability and value of the very few pristine island faunas that still remain

Willow coppice systems in short rotation forestry: Effects of plant spacing, rotation length and clonal composition on biomass production

Abstract: Above ground biomass production was determined for ten Salix clones grown in pure and mixed stands at a square spacing of 1 m and seven rotation periods (1 to 6 and 8 years), and of one clone grown at four square spacings (0.5, 0.6, 0.7 and 1 m), with rotation cycles of 1 to 5 years. Most clones reached a maximum mean annual increment (8 to 14 tons dry matter ha −1 yr −1 ) under a rotation period of 4 to 5 years. Densely spaced stands exhibited a higher production than wider spacings during the first harvests under the shortest rotation periods. Neither in later harvests of short cycles (1 to 3 years) nor in any harvests of longer cycles (> 3 years) did spacing affect biomass production. Some clones suffered from leaf rust and grazing by roe deer. Clone mixtures showed a higher biomass production in the later stages due to the compensatory effect of the successful clones which, when growing in mixtures, could fill out the gaps left by individuals that suffered from impacts other than competition. We conclude that extremely short rotations (1 to 2 years) are unsuitable for Swedish conditions, and that 4- to 6-year rotations perform best. In such longer rotations, biomass production of stands with 2 × 10 4 plants per hectare equals the production of denser stands.

Microbial biomass P, labile P, and acid phosphatase activity in the humus layer of a spruce forest, after repeated additions of fertilizers

Abstract: A 20-year-old forest fertilization trial was used to investigate the effects of repeated P additions on P availability in the humus layer of a Norway spruce forest soil N was supplied annually, and P, K, and micronutrients were supplied every 4th year The last P application was made 2 years before the investigation started Microbial P concentrations in the P+NK+micro-amended plots were about half as high as those in the control and the N-only treatment In plots without P amendments, around 50% of the total P in the humus layer was found in microorganisms, whereas in P-amended plots the figure was around 25% The block supporting more rapid tree growth, situated on the middle of a slope, showed a significantly higher microbial biomass P concentration than the less productive block at the bottom of the slope Labile P concentrations did not vary between treatments and thus could not have directly contributed to the treatment-related differences in total microbial biomass P Acid phosphatase activities were around three times lower in the sites treated with P+NK+micro-nutrients Two sources are suggested for the acid phosphatases, active excretion by living roots and fungi and passive release from ruptured cells For all eight plots investigated, there was a positive correlation (R=083) between acid phosphatase activity and the microbial P concentration The P concentration in current-year needles was the lowest in the N-only treatment at 1,13 mg g-1 dry weight, and the highest in the P+NK + micronutrients + lime treatment at 192 mg g-1 dry weight The P:N ratio in needles varied from 0115 in the P+NK + micronutrients + lime plots to 0068 in the N-only plots The latter value is at the level where P is considered to be the growth rate-determining nutrient

The Role of the Endoplasmic Reticulum in Protein Synthesis, Modification and Intracellular Transport

Abstract: The endoplasmic reticulum (ER) is the port of entry of the protein secretory pathway. Proteins destined for the cell wall, the vacuole or for the other compartments of the endomembrane system are first inserted into the ER and then transported to the Golgi complex en route to their final destinations. The ER is the compartment where newly-synthesized polypeptides fold, where many multimeric proteins assemble and where glycoproteins acquire their asparagine-linked glycans. The ER also provides a protein quality control function and proteins are usually retained in this compartment until they have acquired their correct conformation

Response of small birch plants (Betula pendula Roth.) to elevated CO2 and nitrogen supply

Abstract: Small birch plants were grown for up to 80 d in a climate chamber at varied relative addition rates of nitrogen in culture solution, and at ambient (350 μmol mol-1) or elevated (700 μmol mol-1) concentrations of CO2. The relative addition rate of nitrogen controlled relative growth rate accurately and independently of CO2 concentration at sub-optimum levels. During free access to nutrients, relative growth rate was higher at elevated CO2. Higher values of relative growth rate and net assimilation rate were associated with higher values of plant N-concentration. At all N-supply rates, elevated CO2 resulted in higher values of net assimilation rate, whereas leaf weight ratio was independent of CO2. Specific leaf area (and leaf area ratio) was less at higher CO2 and at lower rates of N-supply. Lower values of specific leaf area were partly because of starch accumulation. Nitrogen productivity (growth rate per unit plant nitrogen) was higher at elevated CO2. At sub-optimal N-supply, the higher net assimilation rate at elevated CO2 was offset by a lower leaf area ratio. Carbon dioxide did not affect root/shoot ratio, but a higher fraction of plant dry weight was found in roots at lower N-supply. In the treatment with lowest N-supply, five times as much root length was produced per amount of plant nitrogen in comparison with optimum plants. The specific fine root length at all N-supplies was greater at elevated CO2. These responses of the root system to lower N-supply and elevated CO2 may have a considerable bearing on the acquisition of nutrients in depleted soils at elevated CO2. The advantage of maintaining steady-state nutrition in small plants while investigating the effects of elevated CO2 on growth is emphasized.

Inhibition of enterobacteria and Listeria growth by lactic, acetic and formic acids

Abstract: Minimum inhibitory concentrations (MIC) of undissociated lactic, acetic and formic acids were evaluated for 23 strains of enterobacteria and two of Listeria monocytogenes. The evaluation was performed aerobically and anaerobically in a liquid test system at pH intervals of between 4.2 and 5.4. Growth of the enterobacteria was inhibited at 2-11 mmol l-1, 0.5-14 mmol l-1 and 0.1-1.5 mmol l-1 of undissociated lactic, acetic and formic acids, respectively. The MIC value was slightly lower with anaerobic conditions compared with aerobic conditions. The influence of protons on the inhibition was observed for acetic acid at the low pH values. Undissociated lactic acid was 2 to 5 times more efficient in inhibiting L. monocytogenes than enterobacteria. Acetic acid had a similar inhibitory action on L. monocytogenes compared with enterobacteria. Inorganic acid (HCl) inhibited most enterobacteria at pH 4.0; some strains, however, were able to initiate growth to pH 3.8. The results indicate that the values of undissociated acid which occur in a silage of pH 4.1-4.5 are about 10-100 times higher than required in order to protect the forage from the growth of enterobacteria and L. monocytogenes.