水稻"三控"施肥技术规程

从氮肥总量控制、氮肥的分阶段调控、磷钾肥的施用和其他配套技术等方面,介绍了水稻"三控"施肥技术规程:并指出应用水稻"三控"施肥技术规程中应注意的问题.     

Relative abundance and fungicide resistance patterns of Botrytis cinerea and B. pseudocinerea on apple in Northern Germany

Journal of Plant Diseases and Protection - In the Lower Elbe region of Northern Germany, low levels of fungicide resistance were recorded among Botrytis isolates obtained from blossom-end rot...     

In ovo leptin administration affects hepatic lipid metabolism and microRNA expression in newly hatched broiler chickens

Background

A leptin-like immunoreactive substance has been found in chicken eggs and has been implicated in serving as a maternal signal to program offspring growth and metabolism. In the present study, we investigated the effects of in ovo leptin administration on hatch weight, serum and hepatic concentrations of metabolites and hormones, as well as on the expression of genes involved in hepatic lipid metabolism and the predicted microRNAs (miRNAs) targeting the affected genes. To this end we injected fertile eggs with either 0.5 μg of recombinant murine leptin or vehicle (PBS) before incubation.

Results

Prenatally leptin-exposed chicks showed lower hatch weight, but higher liver weight relative to the body weight, compared to the control group. In ovo leptin treatment increased the hepatic content and serum concentration of leptin in newly hatched chickens. The hepatic contents of triglycerides (TG) and total cholesterol (Tch) were decreased, whereas the serum levels of TG, Tch and apolipoprotein B (ApoB) were increased. The hepatic mRNA expression of sterol regulator element binding protein 1 (SREBP-1c), SREBP-2, hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) and cholesterol 7α-hydroxylase 1 (CYP7A1) was significantly up-regulated, as was the protein content of both SREBP-1c and SREBP-2 in hepatic nuclear extracts of leptin-treated chickens. Moreover, out of 12 miRNAs targeting SREBP-1c and/or HMGCR, five were significantly up-regulated in liver of leptin-treated chicks, including gga-miR-200b and gga-miR-429, which target both SREBP-1c and HMGCR.

Conclusions

These results suggest that leptin in ovo decreases hatch weight, and modifies hepatic leptin secretion and lipid metabolism in newly hatched broiler chickens, possibly via microRNA-mediated gene regulation.     

Transcatheter Atrial Septal Defect Closure with the AMPLATZER® Atrial Septal Occluder in 13 Dogs: Short- and Mid-Term Outcome

Background: Transcatheter atrial septal defect (ASD) closure in the dog was first reported in 2005.
Objectives: Describe the technique and both short- and mid-term outcome of transcatheter ASD closure with the Amplatzer^® atrial septal occluder (ASO).
Animals: Thirteen client-owned dogs with ASD.
Methods: Records of the initial 13 dogs in which transcatheter ASD closure was attempted at Texas A&M University were reviewed.
Results: All dogs had hemodynamically relevant septum secundum ASD. Two dogs had concurrent congenital abnormalities. ASOs were deployed in 13 dogs and released in 12. Eleven were released by a right jugular approach and 1 by a transatrial approach through a right lateral thoracotomy. Transthoracic echocardiographic estimates of ASD size were 14.0 ± 5.4 mm (mean ± 1 standard deviation) with a range of 7–22 mm. Accidental right atrial release occurred in 1 dog and embolization after release occurred in 2 dogs. Transcatheter ASD closure was successful in 10 dogs. Transthoracic color Doppler echocardiography the day after ASD closure indicated complete occlusion in 5 dogs, trivial to mild residual shunting in 4 dogs, and moderate residual shunting in 1 dog. Follow-up echocardiograms (mean of 12.4 ± 7.4 months postprocedure) were available for 9 dogs. There was no residual ASD shunting in 6 dogs. In 3 of the 5 dogs with postoperative residual shunting it was judged to be decreased and hemodynamically unimportant relative to the dogs' postoperative evaluations. The mean length of event-free survival in the 10 dogs that underwent successful transcatheter ASD closure was 22.2 ± 10.2 months.     

Rapid shift from denitrification to nitrification in soil after biogas residue application as indicated by nitrous oxide isotopomers

Nitrous oxide (N₂O) is one of the major greenhouse gases emitted from soils, where it is mainly produced by nitrification and denitrification. It is well known that rates of N₂O release from soils are mainly determined by the availability of substrates and oxygen, but N₂O source apportioning, highly needed to advance N₂O mitigation strategies, still remains challenging. In this study, using an automated soil incubation system, the N₂O site preference, i.e. the intramolecular ¹⁵N distribution, was analyzed to evaluate the progression in N₂O source processes following organic soil amendment. Biogas fermentation residue (BGR; originating from food waste fermentation) was applied to repacked grassland soil cores and compared to ammonium sulfate (AS) application, both at rates equivalent to 160 kg NH₄⁺-N ha⁻¹, and to unamended soil (control). The soil cores were incubated in a helium-oxygen atmosphere with 20 kPa O₂ for 43 days at 80% water-filled pore space. 43-day cumulative N₂O emissions were highest with BGR treated soil accounting for about 1.68 kg N₂O-N ha⁻¹ while application of AS caused much lower fluxes of c. 0.23 kg N₂O-N ha⁻¹. Also, after BGR application, carbon dioxide (CO₂) fluxes showed a pronounced initial peak with steep decline until day 21 whereas with ammonium addition they remained at the background level. N₂O dual isotope and isotopomer analysis of gas samples collected from BGR treated soil indicated bacterial denitrification to be the main N₂O generating process during the first three weeks when high CO₂ fluxes signified high carbon availability. In contrast, in the second half after all added labile carbon substrates had been consumed, nitrification, i.e. the generation of N₂O via oxidation of hydroxylamine, gained in importance reaching roughly the same N₂O production rate compared to bacterial denitrification as indicated by N₂O SP. Overall in this study, bacterial denitrification seemed to be the main N₂O forming process after application of biogas residues and fluxes were mainly driven by available organic carbon.     

Measuring nitrogen fixation by <Emphasis Type="Italic">Sesbania sesban</Emphasis> planted fallows using <Superscript>15</Superscript>N tracer technique in Kenya

A field experiment was performed in eastern Kenya to estimate N₂ fixation by Sesbania sesban over an 18-month period using the ¹⁵N dilution method. The influence of three reference species, Senna spectabilis, Eucalyptus saligna and Grevillea robusta, on the estimates of N₂ fixation was also assessed. Percentage Ndfa (nitrogen derived from the atmosphere) was calculated based on foliar atom excess (FAE), above-ground atom excess (AAE) or whole tree atom excess (WAE) data. The differences in atom% ¹⁵N excess values between species and plant parts are presented and discussed. We recommend the use of several reference species for estimating %Ndfa and that the different results obtained should be carefully considered in relation to the issues being addressed. In this study, Senna was the most suitable of the three reference species because its N uptake pattern and phenology were very similar to those of Sesbania. When well established, the amount of N fixed by Sesbania accounts for more than 80% of its total N content, according to FAE-based estimates. We estimated the Ndfa by Sesbania after 18 months to between 500 and 600 kg ha⁻¹ , depending on whether FAE, AAE or WAE data were used and on the choice of reference species. The substantial accumulation of N in planted Sesbania highlighted its potential to increase the sustainability of crop production on N-limited soils. We consider the ¹⁵N dilution method to be appropriate for quantifying N₂ fixation in improved fallows in studies, similar to this one, of young trees with high N₂-fixing ability.     

Effects of tension wood on specific conductivity and vulnerability to embolism of Quercus ilex seedlings grown at two atmospheric CO2 concentrations

To determine whether there are decreases in hydraulic function of a woody stem when it has increased mechanical loading, Quercus ilex L. seedlings were grown upright or inclined to force the production of large amounts of tension wood (TW). Seedlings were grown in ambient or elevated carbon dioxide concentrations ([CO2]) for 16-17 months to provide two sets of seedlings differing in growth rates and allocation patterns. In both CO2 environments, inclination caused formation of large amounts of TW at the base and mid-section of most stems, but not at the stem tips. Contrary to expectation, there were no significant effects of stem inclination or amount of TW on specific conductivity (k(s)) or vulnerability to embolism. Samples with high amounts of TW had higher vessel frequency, similar average vessel lumen area, similar vessel lumen fraction (6% of the transverse area), elevated frequency of vessels in the smallest diameter class, and higher wood density than samples with very little TW. Samples from seedlings in the elevated [CO2] treatment had similar vessel frequency, larger average vessel lumen area (caused by a higher frequency of large-diameter vessels), similar vessel lumen fraction, and similar wood density as samples from seedlings in the ambient [CO2] treatment. There was a strong position effect: the highest wood density and lowest ks were at the stem base, intermediate values were at the middle, and the lowest density and highest ks were at the stem tip. We conclude that, in a species that uses different cells for mechanical support and water transport, there can be large modifications in performance of the mechanical function through TW formation without impacting the water transport functions-ks and vulnerability to embolism.     

Regeneration niches of Norway spruce (<Emphasis Type="Italic">Picea abies</Emphasis> [L.] Karst.) saplings in small canopy gaps in mixed mountain forests of the Bavarian Limestone Alps

Natural regeneration measurements are the main silvicultural objective in overaged protective forests of the Bavarian Limestone Alps. While manifold problems with these stands, especially the impact of browsing, are widely recognised, the regeneration niches of Norway spruce (Picea abies [L.] Karst.) are insufficiently known. The purpose of this study was to determine favourable combinations of site factors for the development of spruce in small, unfenced canopy gaps, located on Aposerido-Fagetum caricetosum albae forest sites. We recorded the occurrence of spruce saplings (as dependent variable) and of six site factors (as independent variables) on 480 0.5 m²-subplots. In addition, we estimated the coverage of six acid adapted plant species to determine correlations with the humus depth. A binary logistic regression analysis was used to predict the probability of the occurrence of a spruce sapling in dependency of the different site factors. Supported by other studies, we assumed that the supply of solar radiation was adequate for the sufficient regeneration of spruce within the canopy gaps. Other site factors significantly determined the regeneration niches of spruce saplings. More spruce saplings were found near hindrances and on rough surfaces than would be expected from a random occurrence of saplings. These microsite types may have characteristics, especially protection against snow gliding that promotes spruce establishment. A calculated “hindrance index”, which accounted for the number, and the distance of surrounding hindrances might be a good specific value to describe the influence of hindrances on steep slopes. The sapling establishment decreased on thin humus layers. Our assumption for the sites was that thick organic layers might represent a good seedbed for spruce. Decayed dead wood was scarce, but was exceedingly favoured by spruce saplings. Results obtained suggest that the natural regeneration establishment of spruce on steep slopes can be successfully influenced by site factors which inhibit the influence of snow gliding. According to a “positive microsite” concept, we recommend for artificial regeneration measurements with spruce, microsites close to hindrances (e.g. stumps, downed trees) and Vaccinium myrtillus as a predictor for thick, acid humus layers.     

How low can you go? Physical production mechanism of elephant infrasonic vocalizations

Elephants can communicate using sounds below the range of human hearing ("infrasounds" below 20 hertz). It is commonly speculated that these vocalizations are produced in the larynx, either by neurally controlled muscle twitching (as in cat purring) or by flow-induced self-sustained vibrations of the vocal folds (as in human speech and song). We used direct high-speed video observations of an excised elephant larynx to demonstrate flow-induced self-sustained vocal fold vibration in the absence of any neural signals, thus excluding the need for any "purring" mechanism. The observed physical principles of voice production apply to a wide variety of mammals, extending across a remarkably large range of fundamental frequencies and body sizes, spanning more than five orders of magnitude.     

Photonic crystal light collectors in fish retina improve vision in turbid water

Despite their diversity, vertebrate retinae are specialized to maximize either photon catch or visual acuity. Here, we describe a functional type that is optimized for neither purpose. In the retina of the elephantnose fish (Gnathonemus petersii), cone photoreceptors are grouped together within reflecting, photonic crystal-lined cups acting as macroreceptors, but rod photoreceptors are positioned behind these reflectors. This unusual arrangement matches rod and cone sensitivity for detecting color-mixed stimuli, whereas the photoreceptor grouping renders the fish insensitive to spatial noise; together, this enables more reliable flight reactions in the fish's dim and turbid habitat as compared with fish lacking this retinal specialization.