Effects of silver nanoparticles on the microbiota and enzyme activity in soil

To assess the impact of silver nanoparticles (SNP) on soil microbial biomass, microbial activity, and enzyme activities, a medium‐term experiment over four months was performed in which soil was applied with increasing SNP‐application rates compared to a control. The treatments included a single SNP‐application dose analogous to 3.2 (SNP‐1), 32 (SNP‐10), and 320 (SNP‐100) μg Ag (kg dry soil)^–1 and a control without SNP application, respectively. At the end of the experiment, clear evidence was found that microbial biomass was significantly decreased with increasing SNP‐application rate, while basal respiration was increased in this direction. In addition, metabolic quotients were increased in the SNP treatments compared to the control. This is at least circumstantial evidence that the efficiency of substrate use was lowered in SNP‐treated soils. Another suggestion might be that after four months microbial‐community composition was changed due to SNP. No treatment effects were found for microbial biomass N, fluorimetric enzymes, and the abiotic soil parameters pH and soil organic C.     

Effect of air‐drying on phosphorus fractions in clay soil

Despite the publication of a number of papers dealing with the effect of drying on the soil labile P pool, less attention has been paid to the possible drying‐evoked changes in the more stable P pools. We applied Hedley's sequential fractionation procedure that aims at quantifying soil P reserves according to their decreasing plant availability to examine the effects of drying on soil P fractions in clayey soil samples of different cultivation history. To further investigate the contribution of organic matter disruption to the solubility of soil P, the P extracted in each fractionation step was divided into two size classes by filtering the suspension through a 0.2 μm membrane filter. There were no air‐drying‐induced changes in the total amount of P extracted in each fractionation step. However, air‐drying changed the distribution of water‐extractable P in size fractions; increase in the small‐sized P took place at the expense of large‐sized P. Air‐drying increased also small‐sized molybdate‐unreactive P (MUP) in the NaOH fraction giving evidence that drying‐induced alterations take place also in less labile P forms. The results revealed that air‐drying alters the extractability and distribution of P in various pools rather than the total amount of extracted P and that a large proportion of H₂O‐ and NaOH‐extractable large‐sized MUP may remain undetected if only filtered samples are analyzed.     

Linarin, a selective acetylcholinesterase inhibitor from Mentha arvensis

Linarin (acacetin-7-O-beta-d-rutinoside) from the flower extract of Mentha arvensis showed selective dose dependent inhibitory effect on acetylcholinesterase.     

Ozone impairs autumnal resorption of nitrogen from birch (Betula pendula) leaves, causing an increase in whole-tree nitrogen loss through litter fall

Saplings of one half-sib family of birch, Betula pendula Roth, were exposed to three ozone concentrations (non-filtered air (NF); non-filtered air + 10-20 nmol O(3) mol(-1) (NF+); non-filtered air + 40-60 nmol O(3) mol(-1) (NF++)) in open-top chambers during two growing seasons from 1997 to 1998. Shed leaves were collected regularly during both growing seasons and, in 1998, the dry mass (DM) and nitrogen (N) concentrations ([N]) of the shed leaves were measured to quantify the total amount of N lost through litter fall. Dry mass and [N] were also determined in mid-August for attached, mature and non-senescent leaves, in order to estimate autumnal leaf N resorption efficiency and proportional leaf DM decrease. Net photosynthetic capacity was measured during August and September 1998, in a population of leaves that emerged in mid-July. Photosynthesis declined with increasing leaf age in the NF++ treatment, whereas it remained high throughout the measurement period in the NF and NF+ treatments. In both years, leaves abscised prematurely in the NF++ treatment, whereas this effect was only significant in 1998 in the NF+ treatment. There was a strong linear relationship between proportional leaf shedding and daylight ozone exposure above a threshold of 40 nmol mol(-1) (daylight AOT40) during the growing season. The resorption of N was significantly impaired by ozone, and the smaller autumnal decrease in leaf DM in elevated ozone concentrations suggested that the bulk resorption of leaf DM was also inhibited. Nitrogen resorption efficiencies were 81, 73 and 63% and leaf mass decreases were 45, 36 and 30% in the NF, NF+ and NF++ treatments, respectively. Compared with the NF treatment, total N loss through litter fall was increased by 16 and 122% in the NF+ and NF++ treatments, respectively. We conclude that ozone impaired N resorption from birch leaves before abscission, causing a substantial increase in whole-tree N loss through litter fall.     

Antioxidant and free radical scavenging activities of five moss species

Total phenolic content, reducing power, antioxidant and free radical scavenging activities of ethanol extracts of five mosses were determined in vitro. No correlation between the total phenolic content and antioxidant or scavenging activities was found.     

Critical night length for bud set and its variation in two photoperiodic ecotypes of Betula pendula

We studied the variation in critical night length for bud set in two photoperiodic ecotypes (two latitudinally distant stands) of silver birch (Betula pendula Roth) in three phytotron experiments. Seeds from 21 open-pollinated mother trees in a southern (Tuusula, 60 degrees N) and a northern (Kittil?, 67 degrees N) Finnish stand were germinated and grown for 4 weeks in a 24-h photoperiod in a greenhouse and then moved to different night length treatments at 18 degrees C for 4 to 6 weeks. Night lengths from 5 to 8.5 h were used for southern origin seedlings and from 1 to 4.5 h for northern origin seedlings. At the end of the treatments, apical bud set was observed and the percentage of seedlings with bud set calculated for each treatment and tree progeny. The critical night lengths (CNL) for 50% bud set were determined separately for seedlings from each mother tree by regression analysis. In both ecotypes, the mean percentage of seedlings with bud set was lowest for the shortest night lengths and increased rapidly as night lengths increased. Mean CNL with its 95% confidence interval for the southern and northern ecotypes was 6.3 +/- 0.2 and 3.1 +/- 0.3 h, respectively. The CNL of the two ecotypes differed significantly in three experiments. Within-ecotype variance of the CNL was significantly higher in the northern ecotype (0.484) than in the southern ecotype (0.150). Significant differences in CNL were detected between individual mother trees of the southern ecotype, but not between mother trees of the northern ecotype. The ranking of individual mother trees, based on CNL, differed in the three experiments.     

Phytate degradation in a mixture of ground wheat and ground defatted soybeans during feed processing: effects of temperature, moisture level, and retention time in small- and medium-scale incubation systems

The optimal conditions for degradation of phytate (IP6, myo-inositol hexaphosphate) in a mixture of ground wheat and ground defatted soybeans (1:2, w/w) with added exogenous E. coli phytase were investigated at different temperatures (45, 60, 75, and 95 degrees C), moisture levels (25%, 35%, and 45%), and retention times (2-45 min). All treatment combinations were investigated in a small-scale mixer conditioner (experiment 1). The combined 45 degrees C and 45% moisture treatment was most efficient and reduced the content of IP6 by 86% during 45 min of incubation. This treatment combination was applied in a medium-scale mixer conditioner (experiment 2), and 76% reduction of IP6 at 45 min was obtained. During incubation, the content of lower groups of inositol phosphates, such as IP4 (myo-inositol tetraphosphate) and IP3 (myo-inositol triphosphate), increased significantly as the content of IP6 decreased. The major isomer formed was Ins(1,2,5,6)P(4).     

Positional distribution of conjugated linoleic acid in triacylglycerol of Saccharomyces cerevisiae

Saccharomyces cerevisiae was cultivated in the presence of cis-9,trans-11 or trans-10,cis-12 isomers of free conjugated linoleic acid (CLA), and the effects of the isomers on the regioisomerisms of triacylglycerol (TAG) of the yeast were elucidated. Both isomers constituted about 34% of all fatty acids and increased drastically the number of different TAG species. Nearly all of the species contained CLA in at least one sn-position. In the most abundant species analyzed (20% of total species), the cis-9,trans-11 isomer appeared in combination with monounsaturated fatty acids (C16:1, C:18:1) whereas trans-10,cis-12 isomer was most frequently present with a medium chain fatty acid (C10:0 or C12:0) in the sn-2 position and C16:0 in one of the end positions (14% of total species). With either isomer, the amount of TAG species in which CLA encompassed all sn-positions was ca. 4%. Thus, S. cerevisiae can be used to produce edible single cell oil characterized by very heterogeneous distribution of CLA among the different TAG species.     

Microbially safe utilization of non-inactivated oats (Avena sativa L.) for production of conjugated linoleic acid

A microbially safe process for the enrichment of conjugated linoleic acid (CLA) in oats was developed. The process consists of hydrolysis of oat lipids by non-inactivated oat flour, followed by propionibacterium-catalyzed isomerization of the resulting free linoleic acid to CLA. The first stage was performed at water activity (a(w)) 0.7, where hydrolysis of triacylglycerols progressed efficiently without growth of the indigenous microflora of flour. Thereafter, the flour was incubated as a 5% (w/v) aqueous, sterilized slurry with Propionibacterium freudenreichii ssp. shermanii. The amount of CLA produced in 20 h was 11.5 mg/g dry matter corresponding to 116 mg/g lipids or 0.57 mg/mL slurry. The oat flour had also the capability to hydrolyze exogenous oils at a(w) 0.7. Sunflower oil, added to increase linoleic acid content in triacylglycerols 2.7-fold, was hydrolyzed rapidly. Isomerization of this oil-supplemented flour as a 5% slurry gave final CLA content of 22.3 mg/g dry matter after 50 h of fermentation, corresponding to 118 mg/g lipids or 1.14 mg/mL slurry. Storage stability of CLA in fermented oat slurries at 4 degrees C was good.     

Endocrine characteristics of late pregnant hyperketonaemic ewes and their reproductive performance following the induction of ovarian cyclicity out of the breeding season

Ketosis was diagnosed in a flock of Merino ewes that conceived from synchronised oestrus in the early autumn period. On day 140 of pregnancy the ewes were sampled for determination of betaOH-butyrate (BHB), AST, glucose, non-esterified fatty acids (NEFA), total cholesterol (TCH), insulin, T4, T3, cortisol, IGF-1 and leptin. The results were evaluated according to the number of fetuses born some days later and the presence of hyperketonaemia (BHB: > or = 1.60 mmol/l). In May, about 3 months after lambing, cyclic ovarian function was induced (Cronolone + eCG), and the ewes were inseminated artificially (AI) 48 h after the removal of gestagen-containing sponge. At the time of AI and 10 days later blood samples were collected again to check the plasma levels of the same constituents as previously (in samples taken at AI), and to monitor the ovarian response by assaying progesterone (in both samples). On day 140 of gestation significantly lower BHB levels were detected in dams with single (n = 41) than in those with twin (n = 57) pregnancies. Hyperketonaemia was found only in ewes bearing twins (n = 27). These animals had higher NEFA and cortisol, and lower TCH, insulin, IGF-1, leptin and T3 levels than their normoketonaemic twin-bearing flock-mates, and those with single pregnancy. The blood glucose concentrations varied within a wide range, and the means of groups did not exhibit any significant differences. The formerly hyperketonaemic individuals were characterised by lower leptin level 3 months after lambing, and they showed a poorer response to the cycle-induction procedure than the others. The non-responders had lower IGF-1 and leptin levels than those ovulated after this treatment. It was concluded that the subclinical form of ovine ketosis is characterised by complex endocrine alterations, reflecting an obvious form of negative energy balance. If attempts to induce cyclic ovarian function outside the breeding season are made soon after lambing, the ovarian response and fertility of these ewes may also be depressed.