Perennial ryegrass (Lolium perenne L. cv. Parcour) grown at eight levels of nitrogen (N) fertilization (0–765 mg/pot) was exposed to ambient (390 ppm) and elevated (690 ppm) carbon dioxide (CO2) concentrations for 83 days. Plants were cut three times and dry matter yields determined for each harvest. At final harvest, dry weight of root and stubble biomass was determined, as N concentrations of all plant fractions were determined. Carbon dioxide enrichment effects on yield and total plant biomass increased with increasing N fertilization. The weaker CO2‐related yield enhancement at low N supply was due to the plants inability to increase tiller number. Root fraction of total plant biomass at final harvest was increased by high CO2 and decreased by N supply. Root biomass was significantly increased by CO2 enrichment and for both CO2 treatments the N supply for maximum root mass coincided with the N supply for reaching maximum total plant biomass. A significant correlation between root fraction of total plant dry matter and N concentration of total plant biomass, which was not changed by CO2 enrichment, indicates that biomass partitioning between shoot and root is controlled by the internal N status of the plant. 相似文献
Summary Potato virus S was eliminated from systemically infected stem cuttings of five potato cultivars after three passages in nutrient
media containing 0.003% of the synthetic riboside ribavirin (Virazole). Treatment effects could be detected after only two
passages which also revealed differences in cultivar response. Treated plants transferred to ribavirin-free culture media
and to soil remained PVS-free.
This simple method is less time-consuming than the usual meristem (axillary) tip culture procedures combined with chemotherapy
or heat treatment. 相似文献
Zusammenfassung Auf der Grundlage von Ergebnissen der Pflanzgutkontrolle der Jahre 1979 bis 1988 konnten ca. 77% des Gebietes der ehemaligen
Deutschen Demokratischen Republik in Befallsdruckzonen der ?konomisch relevanten Virusgruppen potato leafroll virus und schwere
Mosaikviren (potao virus A, potato virus M, potato virus Y) eingeteilt werden. Damit wurden die Aussagen von Schick (1952)
und Pfeffer (1956) zur Verteilung der Gesundheits- und Abbaulagen best?tigt. 相似文献
Studies on purebred Nellore cattle and their crosses with Fleckvieh, Chianina, Charolais and the Ibagé breed (5/8 Aberdeen Angus, 3/8 Nellore) during 39 months in the field gave mean daily counts for engorging female ticks of 3.3, 25.2, 22.2, 21.0 and 59.7 per animal respectively. Annual fluctuations were similar in all groups; with the exception of the purebred Nellore mean counts are at levels considered dangerous for the stability of enzootic tick fever. 相似文献
The effects of dietary β‐hydroxy‐β‐methylbutyrate (HMB) supplementation during gestation on reproductive performance of sows and the mRNA expression of myogenic markers in skeletal muscle of neonatal pigs were determined. At day 35 of gestation, a total of 20 sows (Landrace × Yorkshire, at third parity) were randomly assigned to two groups, with each group receiving either a basal diet or the same diet supplemented with 4 g/day β‐hydroxy‐β‐methylbutyrate calcium (HMB‐Ca) until parturition. At parturition, the total and live litter size were not markedly different between treatments, however, the sows fed HMB diet had a decreased rate of stillborn piglets compared with the sows fed the control (CON) diets (p < 0.05). In addition, piglets from the sows fed HMB diet tended to have an increased birth weight (p = 0.08), and a reduced rate of low birth weight piglets (p = 0.05) compared with piglets from the CON sows. Nevertheless, lower feed intake during lactation was observed in the sows fed the HMB diet compared with those on the CON diet (p < 0.01). The relative weights of the longissimus dorsi (LD) and semitendinosus (ST) muscle were higher (p < 0.05) in neonatal pigs from the HMB than the CON sows. Furthermore, maternal HMB treatment increased the mRNA levels of the myogenic genes, including muscle regulatory factor‐4 (MRF4, p < 0.05), myogenic differentiation factor (MyoD) and insulin‐like growth factor‐1 (IGF‐1, p < 0.01). In conclusion, dietary HMB supplementation to sows at 4 g/day from day 35 of gestation to term significantly improves pregnancy outcomes and increases the expression of myogenic genes in skeletal muscle of neonatal piglets, but reduces feed intake of sows during lactation. 相似文献
AIMS: To describe the methods used at the Animal Health Laboratory (AHL, Ministry for Primary Industries) to identify Paranannizziopsis australasiensis.
METHODS: Skin biopsy samples from two adult male tuatara were submitted to the AHL in March 2014. Approximately half of each sample was processed for fungal culture and incubated on mycobiotic agar containing cycloheximide at 30°C. Following morphological examination of the culture products, DNA was extracted from suspect colonies. PCR was used to amplify the internal transcribed spacer (ITS) region of fungal rRNA using primers ITS1 and ITS4. Positive amplicons were subjected to DNA sequencing and the results were compared to published sequences. In addition, DNA was extracted from the remaining skin samples and the same PCR was carried out to compare the results.
RESULTS: After 7 days of incubation, colonies morphologically resembling P. australasiensis were observed. DNA extracted from these isolates tested positive for P. australasiensis by PCR and DNA sequencing. Samples of DNA extracted directly from the infected skin samples tested negative for P. australasiensis using the generic fungal PCR.
CONCLUSIONS AND CLINICAL RELEVANCE: Isolation and identification of P. australasiensis was carried out using a combination of fungal culture and molecular testing available at AHL. Results were available in significantly less time than in the past, when isolates had to be sent overseas. PCR and sequencing of fungal isolates is a valuable tool for identification of species that have few, if any, unique macroscopic or microscopic features to aid identification. Further sampling from captive and wild New Zealand reptiles will provide important information on the epidemiology of P. australasiensis, and the conservation and management implications for tuatara and other native reptile species. 相似文献
Vesta's surface is characterized by abundant impact craters, some with preserved ejecta blankets, large troughs extending around the equatorial region, enigmatic dark material, and widespread mass wasting, but as yet an absence of volcanic features. Abundant steep slopes indicate that impact-generated surface regolith is underlain by bedrock. Dawn observations confirm the large impact basin (Rheasilvia) at Vesta's south pole and reveal evidence for an earlier, underlying large basin (Veneneia). Vesta's geology displays morphological features characteristic of the Moon and terrestrial planets as well as those of other asteroids, underscoring Vesta's unique role as a transitional solar system body. 相似文献
A seven-year old Australian Shepherd, suffering from idiopathic epilepsy under treatment with phenobarbitone and potassium bromide, was presented with generalised lower motor neuron signs. Electrophysiology and muscle-nerve biopsies revealed a neuromyopathy.The serum bromide concentration was increased more than two-fold above the upper reference value.Clinical signs disappeared after applying diuretics and reducing the potassium bromide dose rate. This is the first case report describing electrophysiological and histopathological findings associated with bromide induced lower motor neuron dysfunction in a dog. 相似文献