Showing papers by "Swedish University of Agricultural Sciences published in 1987"
TL;DR: In this article, a soil nitrogen model emphasizing mineral nitrogen dynamics and losses is presented, which has a one-dimensional layered structure and considers plant uptake, mineralization, immobilization, leaching and denitrification processes.
530 citations
TL;DR: In this paper, both zero-and first-order regression models were applied to results from a field experiment on the decomposition of barley straw, incubated 10-15 cm below the soil surface in a barley field.
Abstract: Models were applied to results from a field experiment on the decomposition of barley straw, incubated 10-15 cm below the soil surface in a barley field. Litter bags were sampled 14 times during a 2-yr period to follow the dynamics of total mass and chemical components, e.g., water-solubles and total N. Zero- and first-order regression models were fitted to total mass, with and without adjustment for ambient temperature. R2, adjusted for the number of model parameters, was used for comparisons of model fits. The first-order model showed a good fit (R2 = 0.9875) if days with mean soil temperatures ?00C were excluded. An improved fit was obtained using a temperature correction with QI0 = 1.21 (R2 = 0.9913). A one-compartment simulation model, using temperature and moisture as driving variables, showed a further improved fit (R2 = 0.9952) and a best Q10 = 1.78. Parallel and consecutive first-order models with two components did not improve the overall fit (R2 = 0.9896), but the initial loss of water-solubles coincided well with the predicted initial loss from the labile fraction. To describe the dynamics of selected chemical components, a four-compartment sim- ulation model, including decomposition product formation, was fitted to total mass, water- solubles and total nitrogen. The observed dynamics of these components were well repro- duced by the model. Influences of experimental and statistical techniques on interpretations of model results are discussed.
255 citations
TL;DR: The 30K protein of tobacco mosaic virus was localized to the plasmodesmata of infected tobacco leaves by immunogold cytochemistry, and no specific label was found in the nuclei or at any other site in the cells.
252 citations
TL;DR: It is shown that a formula derived for the root: shoot ratio can also be applied under non-steady-state conditions and agreement is good but more exact knowledge of the relationship between nutrient status and photosynthesis is needed.
Abstract: It is shown how root : shoot ratios can be derived from two plant characteristics, (i) the nitrogen productivity (amount of biomass produced per unit of nitrogen in the biomass and per unit of time) and (ii) the relationship between photo-synthetic rate and internal nitrogen concentration. Derived root: shoot ratios are compared with experimental data for seedlings of seven tree species grown with stable internal nitrogen concentrations. Agreement is good but more exact knowledge of the relationship between nutrient status and photosynthesis is needed. It is shown that a formula derived for the root: shoot ratio can also be applied under non-steady-state conditions.
234 citations
TL;DR: In this paper, a series of general concepts in modelling plant nutrition and growth are exemplified with laboratory and field experiments with steady state nutrition, mainly of forest tree species, and the experimental results suggest that plant nutrient requirements can be defined by two variables: complete nutrient proportions in plant and fertilizer and rate of application of fertilizer to support current growth.
198 citations
TL;DR: In this article, the authors determined the way in which the probability of windthrow depends on parameters that can be affected by forest management, viz. rotation age, thinning program, choice of species, spatial distribution of stands and drainage.
Abstract: In 1981 a storm caused windthrow of 3 million cubic meters of softwood in Denmark, equal to the normal removals of three years. The object of the present analysis is to determine the way in which the probability of windthrow depends on parameters that can be affected by forest management, viz. rotation age, thinning programme, choice of species, spatial distribution of stands and drainage. An empirical data set from 612 stands is used in the estimations. It is found that the windthrow probability is negatively affected by tree diameter, drainage, the time since last thinning and the protection from other stands. The probability increases with tree height, age and relative thinning volume in the latest thinning. Picea is more stable than Abies and Pseudotsuga.
186 citations
TL;DR: D disease risk predictions based on the distance of a tree from various infection sources correlated well with observed frequencies of rot, and the same fungal clone was found to be infecting adjacent trees from several old‐growth stumps.
Abstract: Two Norway spruce stands with heavy infections of Heterobasidion annosum were clear‐cut in 1957 and 1959 in Sweden. The stumps were extracted, the soil sifted to remove most of the roots, and young Norway spruce were planted. After 25 and 28 years, H. annosum had infected 1 % and 2% of trees on plots where stumps had been removed and 17 % and 12% of the trees on control plots, respectively. Several of the H. annosum clones fruiting on old‐growth stumps were also detected in decayed, standing trees. The same fungal clone was found to be infecting adjacent trees from several old‐growth stumps. In addition to old stumps, stumps from recent thinnings and diseased living trees were traced as infection sources. Their relative importance in spreading disease was estimated. Disease risk predictions based on the distance of a tree from various infection sources correlated well with observed frequencies of rot.
150 citations
TL;DR: Effects of full-fat crushed rapeseed on rumen and total digestion, rumen biohydrogenation, and rumen microbial protein synthesis were studied in lactating cows to find out whether these effects are detrimental or beneficial to rumen metabolism.
150 citations
TL;DR: Several key predators which are abundant in spring cereal fields at a time when R. padi emigrants arrive in the crop and which feed on R.padi during the aphids' establishment phase, are identified and are suggested to be faster at higher temperatures than the rate of elimination of prey solids from the guts.
Abstract: SUMMARY
Polyphagous predators (e.g. Araneae, Carabidae and Staphylinidae), collected from spring barley fields during 1981-85, were examined by either gut dissection or a R. padi-specific antiserum in enzyme linked immunosorbent assay (ELISA) in order to detect predation of Rhopalosiphum padi during the aphids' establishment and exponential growth phases.
Overall 18% of c. 3000 carabids dissected were shown to feed on R. padi during the aphids' pre-peak period. No overall relationship was found between percentage carabids with R. padi in the diet and peak R. padi densities. Relatively high proportions of Bembidion spp. (particularly B. lampros) and Pterostichus cupreus fed on R. padi during the aphids' establishment phase, and proportions of those predator taxa containing R. padi increased with increasing R. padi densities in both high and low aphid density years. P. melanarius and Harpalus rufipes mainly fed on R. padi during the aphids' exponential growth phase.
Overall 11% of c. 1350 predators examined in ELISA gave positive reactions to the R. padi antiserum. Relatively high proportions of linyphiid and lycosid spiders were positive throughout the aphid pre-peak period. Several Acari, Opiliones, Trechus spp. (Carabidae), Philonthus spp. (Staphylinidae), Cantharidae and Chilopoda were positive mainly during the aphids' exponential growth phase. Sample sizes were small, however.
Very few of the Bembidion spp. tested in ELISA were positive compared with those examined by gut dissection. The maximum period of R. padi protein (antigen) detection in B. lampros was related to temperature, i.e. 8.5 h at 30°C, 20.5 h at 20°C and 34.5 h at 10°C, respectively. It is suggested that the rate of R. padi protein digestion in B. lampros is faster at higher temperatures than the rate of elimination of prey solids from the guts.
Several key predators (in this case B. lampros, P. cupreus and linyphiid spiders) which are abundant in spring cereal fields at a time when R. padi emigrants arrive in the crop and which feed on R. padi during the aphids' establishment phase, are identified. The results are compared with those from similar investigations elsewhere with predators of Sitobion avenae and Metopolophium dirhodum.
144 citations
TL;DR: It is concluded that one month's adaptation to a high-fat diet results in increased muscle-LPL activity indicating a higher capacity for uptake of fatty acids from circulating serum triglycerides into the muscle cell in association with a greater capacity for triglyceride storage in the muscle.
Abstract: Men with regular physical training habits voluntarily increased their dietary fat intake from 43 to 54% of energy (E%) for four weeks. This was followed by a low-fat (29 E%), high-carbohydrate diet for another four weeks. During the high-fat diet period, the muscle lipoprotein lipase activity (LPLA) increased from 59 +/- 8 to 106 +/- 12 mU/g (mean +/- SE) (P less than 0.05). After the high-carbohydrate diet, LPLA was 57 +/- 16 mU/g, and unchanged relative to the pre-trial value. The triglyceride content in m. vastus lateralis increased from 30 +/- 4 to 47 +/- 9 mmol/kg d.w. (P less than 0.05; mean +/- SE) following the high-fat diet and to 41 +/- 8 following the high-carbohydrate diet. Neither of the diets affected the serum triglyceride and insulin concentrations, nor glucose, glycerol, beta-hydroxybutyrate, citrate and lactate levels in the blood. Nor did they alter enzyme activities in muscle used as markers for the oxidative (citrate synthase, beta-hydroxy-acyl CoA dehydrogenase) and glycolytic (glyceraldehyde phosphate dehydrogenase, lactate dehydrogenase) capacity. It is concluded that one month's adaptation to a high-fat diet results in increased muscle-LPL activity indicating a higher capacity for uptake of fatty acids from circulating serum triglycerides into the muscle cell in association with a greater capacity for triglyceride storage in the muscle. Under these conditions serum triglycerides were not decreased despite the increased muscle LPLA, and serum insulin variations could not explain the change in muscle LPLA.(ABSTRACT TRUNCATED AT 250 WORDS)
143 citations
TL;DR: Paternal inheritance of chloroplast DNA is suggested to be a general phenomenon in conifers, rather than the current belief that it is a specific phenomenon in European larch species.
Abstract: Restriction enzyme analysis was used to determine the inheritance of chloroplast DNA in conifers. The plant material studied included five individual trees of European larch (Larix decidua Mill.) and Japanese larch (Larix leptolepis Sieb. & Zucc.) and six hybrids from controlled crosses between these species. The chloroplast DNA fragment patterns generated by Bam-HI and Bcl-I were species-specific. Paternal inheritance of chloroplast DNA patterns was found in most Larix crosses. One hybrid showed maternal chloroplast DNA patterns. In addition, two other hybrids had mixed Bam-HI patterns suggesting recombination between maternal and paternal chloroplast DNA. The mechanisms favoring paternal inheritance in conifers are not known. Paternal inheritance of chloroplast DNA is suggested it to be a general phenomenon in conifers.
TL;DR: Carbon and nitrogen turnover in soils having continuous inputs of litter is described using theory developed for single cohorts of litter in this paper, where fresh litter is characterized by its quality (how easily it is decomposed by microbes) and its N:C ratio.
Abstract: Carbon and nitrogen turnover in soils having continuous inputs of litter is described using theory developed for single cohorts of litter. Fresh litter is characterized by its quality (how easily it is decomposed by microbes) and its N:C ratio. The decom- position process is described as a continuum and no transition between litter and humus is recognized. Equations are derived for the amounts of carbon and nitrogen in the soil at steady state. Depending upon the microbial production-to-assimilation ratio when substrate of the lowest quality (most-degraded litter) is decomposed, steady state implies either constant or linearly increasing amounts of soil carbon and nitrogen. Comparisons are made between theoretically estimated and observed relations between soil carbon and nitrogen turnover rates for a large range of terrestrial ecosystems, as well as carbon and nitrogen stocks in a Scots pine forest soil.
TL;DR: In this article, the authors measured the decomposition of Scots pine needle litter originating from five stands treated with different amounts of nitrogen fertilizer over a 4-year period in a mature Scots pine forest.
Abstract: Decomposition of Scots pine needle litter originating from five stands treated with different amounts of nitrogen fertilizer was measured over a 4‐year period in a mature Scots pine forest. The litter types, which differed in initial concentrations of nitrogen, phosphorus, potassium, and sulfur, but not in gross organic composition, were studied with respect to mass loss, ingrowth of total fungal mycelium, and net release of nutrients. During the first year of decomposition, rates of mass loss and ingrowth of fungal mycelium were highest in the nutrient‐rich litter. Phosphorus concentration was found to be the main factor affecting mass‐loss rate, and the rate of fungal ingrowth was positively correlated with initial nitrogen concentration. After this initial period, decomposition rates decreased, and after 4 years, accumulated mass loss and amounts of fungal mycelium were similar in all five litter types. These findings may be due, in part, to a lower rate of lignin decomposition in nitrogen‐enriched lit...
TL;DR: Composed of the adjuvant Quil A and immunizing peptides, ISCOM particles contain low concentrations of adjUvant and can significantly enhance immunogenicity, and may be significant part of the future vaccine programmes.
TL;DR: The observed changes in the neocortical and hippocampal EEGs suggest that the present swine were unconscious already when they exhibited motor reactions, and does not exclude the possibility that CO2-independent stress/arousal factors present in a slaughterhouse environment may facilitate the development of motor phenomena similar to seizures.
Abstract: The study is part of a series of investigations performed with the ultimate goal of obtaining an objective evaluation of the ethical aspects and the narcotic efficiency of CO2 inhalation used as pre-slaughter anaesthesia for swine. Six Yorkshire swine were exposed twice to 80% CO2 for 1 min during simultaneous recording of the EEGs from the frontal neocortex, the dorsal hippocampus, and the amygdaloid region via permanently implanted electrodes. In five of the animals myoclonic jerks started at 28 +/- 1 s of CO2 exposure and lasted for 6 +/- 2 s. Neocortical slow wave (delta) activity and increased amplitude of the hippocampal theta (5-7 Hz) waves (i.e. EEG changes seen during the second stage of barbiturate anaesthesia) had developed before the brief period of myoclonic jerks. After this period the EEG activity gradually declined, resulting in neocortical EEG silence at the end of the exposure. This apparent isoelectricity lasted for on average 1 min. The return of the neocortical EEG activity exhibited a pattern reverse to its disappearance, but was much prolonged in comparison to the EEG extinction. Pre-exposure neocortical EEG pattern was not regained until 3-5 min post-exposure. In eight out of 11 experiments the CO2 inhalation also induced hippocampal EEG silence lasting for on average 30 s. EEG flattening was further obtained when recording from the amygdaloid nuclear complex and the adjacent pyriform cortex. The observed changes in the neocortical and hippocampal EEGs suggest that the present swine were unconscious already when they exhibited motor reactions. This does not exclude the possibility that CO2-independent stress/arousal factors present in a slaughterhouse environment may facilitate the development of motor phenomena similar to seizures, with the result that such reactions become manifest before the neocortical EEG exhibits an anaesthesia pattern. The duration of the observed EEG silence implies that, from the ethical point of view, exsanguination might safely be performed within 1 min after the moment when the animal is removed from the high concentration CO2. However, the slow return to a pre-exposure neocortical EEG pattern suggests that the swine remains unconscious for at least another minute.
TL;DR: It is suggested that partial migration can be regarded as a conditional strategy with frequency-dependent choice, and whether this system will result in tactics with equal fitness payoffs is further discussed in relation to the life history consequences of migration and residency.
TL;DR: A method for trapping walking Hylobius abietis (L.) (Coleoptera: Curculionidae) was developed and evaluated and synergy between α‐pinene and ethanol in attracting H. abieti was confirmed.
Abstract: A method for trapping walking Hylobius abietis (L) (Coleoptera: Curculionidae) was developed and evaluated Synergism between α‐pinene and ethanol in attracting H abietis was confirmed The effects of varying release rates of these substances and of adding other host terpenes were studied A simple bait was developed containing α‐pinene and ethanol released from separate vials The correlation between trap catch and seedling damage was estimated during May, June, and August on 1‐, 2‐, and 3‐year‐old clear‐cuttings In May and June, population levels were relatively high on all clear‐cuttings and no significant correlations were found The August experiment showed a strong positive correlation between catch and damage The percentage damaged seedlings per captured weevil was considerably higher in August than in May or June Possibilities for developing a system for forecasting seedling damage using this trapping method are discussed
TL;DR: In this paper, the reproducibility of analytical methods for low molecular weight sugars, starch, soluble- and insoluble dietary fibre (1317), non-starch polysaccharides (NSP) and Klason lignin was tested in an investigation comprising 50 barley samples.
TL;DR: Chinese hamster ovary cells grown in vitro were treated with bleomycin or irradiated with high doses of 60Co gamma rays and DNA strand breaks in single cells were analysed by using the newly introduced microelectrophoretic technique.
Abstract: SummaryChinese hamster ovary cells grown in vitro were treated with bleomycin or irradiated with high doses of 60Co gamma rays (200 and 400 Gy). DNA strand breaks in single cells were analysed by using our newly introduced microelectro-phoretic technique. Bleomycin seems to act in a selective manner so that in some cells the DNA is heavily degraded while in others there is only moderate or no measurable damage. In contrast, a uniform response was found after gamma irradiation. To achieve the same magnitude of DNA fragmentation as in the most severely bleomycin-damaged cells, irradiation with more than 200 Gy is required. Some 8000 double-strand breaks per cell are produced by 200 Gy which will convert the molecular weight of the DNA to the range of 108–109 dalton, and free migration of DNA fragments occurs during electrophoresis. We include also a detailed study of the DNA migration pattern following doses of 0–100 Gy gamma rays.
TL;DR: In this paper, the effect of slash piles on nitrogen leaching was estimated by collecting precipitation and percolating water below slash piles and below the O, E and B horizons of an Orthic Podzol during two growing seasons.
Abstract: Piles of logging residues (slash‐piles) are a consequence of modem logging techniques. The piles cover 10 to 15% of a clear‐felled area. The effect of slash‐piles on nitrogen leaching was estimated by collecting precipitation1 and percolating water below slash‐piles and below the O, E and B horizons of an Orthic Podzol during two growing seasons. Open funnels were used for precipitation, PVC troughs for water leaving the pile and filled‐in zero tension lysimeters for percolating soil water. Exchangeable ammonium and nitrate of humus samples were analysed. The increased nitrogen leaching from the soil below slash‐piles was probably caused by an increased mineralization of the humus layer and a reduced nitrogen uptake by roots.
TL;DR: Half of the 16 Vibrio and Aeromonas strains adhered to the tissue culture cells and to the mucus-coated glass surface and were time-dependent and lost after treatment of the bacteria with heat, proteolytic enzymes or ultra-sound.
Abstract: Tissue culture cells from rainbow trout liver (Rl) and chinook salmon embryo (CHSE) were investigated for the adherence of clinical and environmental isolates of Vibrio anguillarum and Aeromonas hydrophila. Adsorption of these bacteria to a glass surface coated with mucus from fish body surface was also examined. The results showed that half of the 16 Vibrio and Aeromonas strains adhered to the tissue culture cells and to the mucus-coated glass surface. Adhesion and adsorption of these isolates were time-dependent and lost after treatment of the bacteria with heat, proteolytic enzymes or ultra-sound.
TL;DR: Information about leg weakness scored before slaughter and osteochondrosis in elbow and knee joints scored after slaughter in the Swedish pig progeny testing scheme were analysed and only severe joint lesions were correlated with increased incidence of clinical signs of leg weakness.
Abstract: Information about leg weakness scored before slaughter (1 =worst, 3=best) and osteochondrosis in elbow and knee joints scored after slaughter (0=best, 5=worst) in the Swedish pig progeny testing scheme were analysed. The data comprised information on 9 886 pigs (5 568 Landrace and 4318 Yorkshire) beginning test from November 1981 to September 1984. For the two osteochondrosis scores and leg weakness, Landrace was the inferior breed and castrates the inferior sex. The incidence and severity of osteochondrosis was highest in the knee joint, compared with the elbow joint. Only severe joint lesions were correlated with increased incidence of clinical signs of leg weakness. Pigs with inferior constitution grew faster during the first part of the test period, but slower at the end of test compared with constitutionally better pigs. Heritabilities of leg weakness score were 0.14±0.03 for Landrace and 0.11 ±0.03 for Yorkshire. Heritabilities for elbow joint scores for osteochondrosis were 0.21±0.03 and 0...
TL;DR: Allergic dermatitis usually appeared during the third grazing season for imported horses and during the fourth season for horses born in Sweden and the course of the disease tended to become worse with time.
Abstract: A survey of allergic dermatitis (sweet itch) in Sweden contained information on 441 Icelandic horses. Results of a questionnaire indicated that approximately 15 per cent of the country's Icelandic horses suffered from the disease. The prevalence of allergic dermatitis was significantly higher among horses imported from Iceland (26.2 per cent) compared to that of Swedish-born animals (6.7 per cent). In addition, horses born in Iceland were significantly more severely affected than horses born in Sweden. The risk of allergic dermatitis in Sweden appeared to be more than six times higher for horses exported from Iceland to Sweden relative to that of horses originally born in Sweden. The prevalence of disease for horses of seven years or older was 30 per cent for Icelandic-born individuals as compared to 7.3 per cent for horses born in Sweden. Similarly, the risk of allergic dermatitis in Sweden for horses of seven years or older appeared to be nearly 10 times higher for horses imported from Iceland relative to that of horses born in Sweden. Allergic dermatitis usually appeared during the third grazing season for imported horses and during the fourth season for horses born in Sweden. Furthermore, the course of the disease tended to become worse with time. Analysis of the prevalence of allergic dermatitis relative to gender revealed no significant differences. Certain geographical variations in the prevalence of the disease was also found.
TL;DR: Cholesterol oxides were enriched from lipid extracts of fresh and dehydrated egg yolk products by chromatography on Lipidex and TEAP-Lipidex as discussed by the authors.
Abstract: Cholesterol oxides were enriched from lipid extracts of fresh and dehydrated egg yolk products by chromatography on Lipidex and TEAP-Lipidex. Appropriate fractions from TEAP-Lipidex were analyzed by capillary GLC as their TMS derivatives. At the detection limit level, ca 0.2 ppm in total lipids, no cholesterol oxides could be detected in fresh egg yolk. Similarly, spray dried egg yolk powder contained only traces of cholesterol oxides when fresh or stored for 2 months at 4°C. Prolonged storage gave lipid extracts which contained variable levels (0.2–12 ppm) of known oxidation products, viz., cholest-5-ene-3β, 7α-diol, cholest-5-ene-3β, 7β-diol, 5,6α-epoxy-5α-cholestan-3β-ol, 5,6 β-epoxy-5 β-cholestan-3β-01, cholest-5-ene-3β, 20α-diol, 3 β-hydroxycholest-5-en-7-one. Traces or small quantifiable amounts of cholest −5-ene-3β, 25-diol and 5α-cholestane-3β, 5, 6β-triol were observed in some samples at longer storage periods.
TL;DR: In this article, a pre-column derivatization of amino acids in conifer extracts to form 9-fluorenylmethyl formate (FMOC) esters and the subsequent reversed phase high-performance liquid chromatography (HPLC) analysis of these esters have been investigated.
TL;DR: The frequency of nasal contacts between mother and young decreased during the last days of nest occupation, while the frequency of reciprocal contact grunts and “long grunts” from the gilt increased, indicating a change in the character of the mother-young interactions.
TL;DR: In this paper, a model of fungal growth in soil is described, where two biomass components, cell walls and cytoplasm, are considered, and the model predicts that equilibrium levels of active mycelium depend primarily on substrate input rate and yield efficiency and are independent of other parameters controlling substrate availability.
Abstract: A model of fungal growth in soil is described. Two biomass components, cell walls and cytoplasm are considered. Allocation of assimilates to cell wall and cytoplasm synthesis and the relative rate of cytoplasm translocation vary according to C and N availabilities. Model behaviour in relation to substrate supply is examined. For single substrate additions, active mycelium (cytoplasm-filled hyphae) shows a positive correlation to substrate availability, while total hyphal length (cytoplasm-filled + evacuated hyphae) shows an inverse response. For continuous substrate additions, the model predicts that equilibrium levels of active mycelium depend primarily on substrate input rate and yield efficiency and are independent of other parameters controlling substrate availability. Model assumptions about biosynthate allocation and cytoplasm translocation influence N mineralization and immobilization patterns. The model suggests that critical C:N ratios change during decomposition as the fungal biomass develops. The advantages conferred by the mycclial growth form, in terms of conserving energy and nutrient elements in resource-poor environments, are discussed.
TL;DR: In this article, the levels of Mg2+, Ca2+ and Fe2+/Fe3+ were determined in roots and shoots of sugar beet seedlings (Beta vulgaris L. cv. Monohill) cultured for 5 weeks in a complete nutrient solution to which either Cd2+ (0, 5 or 50 μM), EDTA ( 0, 10 or 100 μM) or a combination of both was added.
Abstract: Levels of Mg2+, Ca2+ and Fe2+/Fe3+ were determined in roots and shoots of sugar beet seedlings (Beta vulgaris L. cv. Monohill) cultured for 5 weeks in a complete nutrient solution to which either Cd2+ (0, 5 or 50 μM), EDTA (0, 10 or 100 μM) or a combination of both was added. The plants subjected to the various treatments showed a variety of deficiency symptoms. Leaves of the Cd2+-treated plants became thin and chlorotic (Mg- and Fe-deficiency symptoms). The plants showed reduced growth and developed only a few brownish roots with short laterals (Ca-deficiency symptoms). EDTA treatment resulted in green, stunted, hard leaves and reduced growth (Ca-deficiency symptoms). The deficiency symptoms observed correspond well with the observed uptake rates and distributions of Mg2+, Ca2+ and Fe2+/Fe3+. Increases in either Cd2+, EDTA or a combination of both in the growth medium, were correlated with increasing Mg2+ levels in the roots and with decreasing Mg2+ levels in the shoots. Cd2+ alone or in combination with EDTA had little influence on Ca2+ levels in the shoots but decreased Ca2+ levels in the roots. Thus, Cd2+ affects Mg2+ and Ca2+ transport in opposite ways: Mg2+ transport to the shoots is inhibited while that of Ca2+ is facilitated. Treatment with EDTA alone did not affect Ca2+ concentrations in either the shoots or the roots. Treatment with Cd2+ lowered Fe2+ concentrations in both roots and shoots.
TL;DR: In this paper, the use of lignin as a predictor for the onset of a net nitrogen release was found to be better than the C/N ratio, which is the most commonly used metric for predicting nitrogen release.
Abstract: Nitrogen dynamics were followed in several decomposing forest foliage litters in two contrasting ecosystem types. Litter types showing a significant net accumulation before a net release started were subjected to a study on nitrogen release mechanisms. In all cases no net release of nitrogen took place until a decomposition of the recalcitrant lignin fraction had started. The use of lignin as a predictor for the onset of a net nitrogen release was found to be better than the C/N ratio.
TL;DR: In this article, the effect of barley roots on denitrification was examined, and a pot experiment was designed to compare N2O production and denitification in soils with and without barley plants.
Abstract: To examine the effect of barley roots on denitrification, a pot experiment was designed to compare N2O production and denitrification in soils with and without barley plants. Denitrification, N2O resulting from denitrification and nitrification, and respiration were estimated by incubating pots with soil with and without intact plants in plastic bags at high moisture levels. C2H2-inhibition of nitrous oxide reductase (partial pressure of 10 kPa C2H2) was used to determine total denitrification rates while incubations with ambient air and with C2H2 at partial pressures of 2.5–5 Pa were used to estimate the amounts of N2O released from autotrophic nitrification and from denitrification processes. Other sources of N2O were presumed to be negligible. Potential denitrification, nitrification and root biomass were measured in subsamples collected from four soil depths. A positive correlation was found between denitrification rates and root biomass. N2 was the predominant denitrification product found close to roots; N2O formed by non autotrophic nitrifiers, assumed to be denitrifiers originated in soil not affected by growing roots. Apparently, roots promote denitrification because they consumed oxygen, thereby increasing the anaerobic volume of the soil. The ratio of actual to potential denitrification rates increased over time, especially in the presence of roots.