Influence of nitrogen fertilization on minerals, carbohydrates, amino acids and phenolic compounds in beech (Fagus sylvatica L.) leaves

Beginning in 1985, plots in a 120-year-old beech (Fagus sylvatica L.) stand in the province of Scania, southern Sweden were fertilized annually with ammonium nitrate. In August 1989, leaves from both fertilized and unfertilized trees were analyzed for mineral nutrients, soluble carbohydrates, amino acids and phenolic compounds. Leaf concentrations of total nitrogen were increased by N fertilization. Ammonium was not detected in the leaves, but NO(3) (-) was increased by up to 65% as a result of N fertilization. Nitrogen fertilization decreased foliar concentrations of P and Cu, leading to a nutrient imbalance relative to N. Of the free amino acids, glutamic acid and aspartic acid predominated and, together with glutamine and asparagine, were significantly increased by N fertilization. The concentrations of amides were 2-4 times higher in fertilized trees than in unfertilized trees. Soluble carbohydrates did not change in response to N fertilization, but total phenolic compounds decreased markedly. The reduced concentration of phenolics may explain the greater susceptibility to parasite attacks of trees exposed to N deposition and excess N.     

Mechano-sorptive effects in wooden material

Summary The effects on wood of simultaneous mechanical and moisture loading are studied. In order to clarify the mechano-sorptive behaviour of wood, a review of different phenomena presented in the literature is included. Based on this review a constitutive model is proposed for the case of uniaxial stress in the longitudinal direction. The validity of the model is checked independently against test results. The calculations show that the model is capable of describing the response of wood with reasonable accuracy. Simulations indicate that the response of small test specimens is more difficult to describe than that of larger beams. Some differences in behaviour are found to depend on loading mode and nature of moisture cycling. Very large and fast moisture cycles seem to give larger mechano-sorption than smaller variations. The results of the simulations show that there is a significant influence of strain on the shrinkage and swelling response.     

Tracking leaf area index and coefficient of light extinction over the harvesting cycle of black wattle

The amount of photosynthetic radiation intercepted by a crop is a function of the incident solar radiation on the plants, the leaf area index (L _AI), and the light extinction coefficient (k). We quantified L _AI and k in stands of black wattle (Acacia mearnsii De Wild.) over a 7-year growth cycle at two locations in the state of Rio Grande do Sul, Brazil. Our study was conducted in commercial stands in agroecological regions with high densities of black wattle plantations. L _AI was calculated as the ratio between the leaf area of a tree and its planting space, and k was derived from Beer’s law. L _AI depends on the planting site and stand age. Between the two sites, the L _AI was similar over time, the amount of variation differed. Values of k depended only on stand age, with the highest average observed for stands up to 5 years old. The trend of k during the plantation cycle was inversely proportional to L _AI and was correlated with L _AI, leaf area, leaf dry mass, canopy volume, height, branches dry mass, total dry mass, and crown diameter.     

A method for automatic collimator alignment in microdensity measurements

Summary In microdensitometry, based on X-ray absorption technique and a direct, electronic detector technique, it is usually not possible to observe the collimator and its alignment to the annual ring under investigation during the measurement. In this paper a method for automatic alignment of the collimator to the ring is described. The operating technique is based on an optimization of the resolution of the instrument at every annual ring while the collimator is rotated to the best position. The procedure has been in use a number of years and has proven itself to be efficient and reliable. The theory of operation for the procedure is described and its software structure is shown in a block diagram. Advantages and limitations of the procedure are discussed.The funding of this project is made by Nordbanken. The density profile in Fig. 5 has been recorded by Mr. Bo Larsson and is published with his kind permission     

Evaluation of Bacillus thuringiensis Berliner as an alternative control of small hive beetles, Aethina tumida Murray (Coleoptera: Nitidulidae)

Small hive beetles, Aethina tumida Murray, are parasites and scavengers of honeybee colonies, Apis mellifera L., and have become an invasive species that can cause considerable damage in its new distribution areas. An effective subspecies of Bacillus thuringiensis Berliner (=Bt) would provide an alternative to chemical control of this pest. Therefore, we tested three different Bt strains [B. thuringiensis, var. aizawai (B401^®), B. thuringiensis var. kurstaki (Novodor^®) and B. thuringiensis var. San Diego tenebrionis (Jackpot^®)] and Perizin^® (3.2% coumaphos), each applied on combs with a pollen diet fed to pairs of adult beetles. This evaluates the products for the suppression of successful small hive beetle reproduction. While none of the tested Bt strains showed a significant effect on the number of produced wandering larvae, we could confirm the efficacy of coumaphos for the control of small hive beetles. We further show that it is also efficient when applied with a lower concentration as a liquid on the combs. We suggest the continued search for efficient Bt strains naturally infesting small hive beetles in its endemic and new ranges, which may become a part of the integrated management of this pest.     

Do trees use reserve or newly assimilated carbon for their defense reactions? A 13C labeling approach with young Scots pines inoculated with a bark-beetle-associated fungus (Ophiostoma brunneo ciliatum)

Three-year-old saplings of Pinus sylvestris L. were labeled with ¹³CO₂ prior to inoculating the trunk with Ophiostoma brunneo ciliatum, a blue-staining fungus usually associated to Ips sexdentatus. During incubation, half the trees were submitted to a severe drought that decreased photosynthesis and natural ¹³C content in non-labeled saplings. A large ¹³C-excess was obtained in wood and phloem, especially in the fractions of soluble proteins, starch and soluble sugars of labeled saplings. Drought increased ¹³C-excess, due to reduced photosynthesis and smaller dilution of ¹³C by the addition of newly assimilated ¹²C. The induced-reaction zones in inoculated saplings displayed large total C (58 g 100 g^?1) because of the accumulation of secondary metabolites. They also showed much larger ¹³C-excess than any other compartment: the contribution of stored C to the reaction zones was much higher than that of currently assimilated C. Moreover, drought lowered the contribution of the latter, as shown by the increase of ¹³C in the reaction zones. We conclude that stored C was readily mobilized for the construction of reaction tissues, and that the contribution of currently assimilated C was only minor.     

Homogenization conditions affect the oxidative stability of fish oil enriched milk emulsions: oxidation linked to changes in protein composition at the oil-water interface

Fish oil was incorporated into milk under different homogenization temperatures (50 and 72 degrees C) and pressures (5, 15, and 22.5 MPa). Subsequently, the oxidative stability of the milk and changes in the protein composition of the milk fat globule membrane (MFGM) were examined. Results showed that high pressure and high temperature (72 degrees C and 22.5 MPa) resulted in less lipid oxidation, whereas low pressure and low temperature (50 degrees C and 5 MPa) resulted in faster lipid oxidation. Analysis of protein oxidation indicated that especially casein was prone to oxidation. The level of free thiol groups was increased by high temperature (72 degrees C) and with increasing pressure. Furthermore, SDS-PAGE and confocal laser scanning microscopy (CLSM) indicated that high temperature resulted in an increase in beta-lactoglobulin adsorbed at the oil-water interface. This was even more pronounced with higher pressure. Less casein seemed to be present at the oil-water interface with increasing pressure. Overall, the results indicated that a combination of more beta-lactoglobulin and less casein at the oil-water interface gave the most stable emulsions with respect to lipid oxidation.     

Urine flavonoids and plasma carotenoids in the validation of fruit, vegetable and tea intake during pregnancy in the Norwegian Mother and Child Cohort Study (MoBa)

OBJECTIVE: To validate a new food-frequency questionnaire (FFQ) for measuring the intake of fruit, vegetables and tea reported by women participating in the Norwegian Mother and Child Cohort Study (MoBa). DESIGN: Intake of fruits, vegetables and tea estimated by the FFQ was compared with urinary flavonoid excretion, plasma carotenoid concentration and intake measured by a 4-day weighed food diary (FD). The triangular method was applied to calculate FFQ validity coefficients using two independent biomarkers. SETTING AND SUBJECTS: One hundred and nineteen women participating in MoBa. RESULTS: The FFQ estimate of fruit intake was significantly correlated with urine phloretin (r = 0.33), citrus fruit/juice with urine hesperetin (r = 0.44), cooked vegetables with plasma alpha-carotene (r = 0.37), and tea with urine kaempferol (r = 0.41) (P < 0.01 for all). On average, 60% of the participants fell into the same or adjacent quintiles when classified by FFQ and biomarkers. Significant correlations between the FFQ and FD were found for fruit (r = 0.39), vegetables (r = 0.34), juices (r = 0.50) and tea (r = 0.53). The FFQ validity coefficient was 0.65 for citrus fruit/juice and 0.59 for cooked vegetables as calculated by the triangular method. CONCLUSIONS: The validation study shows that the MoBa FFQ can be used to estimate fruit, juice, vegetable and tea intake in pregnant Norwegian women, and to rank individuals within the distribution.     

Dispersal distances for airborne spores based on deposition rates and stochastic modeling

ABSTRACT A new modeling framework for particle dispersal is explored in the context of the particles being fungal spores dispersed within a field. The model gives rise to both exponentially decreasing and polynomially decreasing two-dimensional densities of deposited fungal spores. We reformulate the model in terms of time to deposition, and show how this concept is equivalent to the deposition rate for fungal spores. Special cases where parameter values for wind and gravitation lead to exponentially or polynomially decreasing densities are discussed, and formulas for one- and two-dimensional densities of deposited spores are given explicitly in terms of parameters for diffusion, wind, gravitation, and spore release height.