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61.
南方菜豆花叶病毒(SBMV)主要有2株系:菜豆株系(SBMV-B)和豇豆株系(SBMV-C),血清学方法不能予以区分。根据已报道的核酸序列设计了2对特异引物,进行RT-PCR扩增并克隆到载体Bluescript中,序列测定予以证实后利用随机引物法合成放射性cDNA探针,再进行体外转译合成地高辛UTP标记的RNA探针。2种探针均可分别特异地检测Northernblot膜上的SBMV-B和SBMV-C。RNA探针检测SBMV-B和SBMV-C灵敏度分别为:0.1μg和0.01μg。 相似文献
62.
Tropical Animal Health and Production - 相似文献
63.
64.
S. Zetterström K. Horzmann J. Yin R. Moon S. Boorman S. Ceriotti A. Wooldridge L. Boone 《Equine Veterinary Education》2022,34(5):e187-e192
A 1-day-old American Paint Horse was presented for a large air-filled mass along the ventral aspect of the neck. Bronchoscopy and oesophagoscopy revealed no sign of communication with the trachea or oesophagus. Radiographs and a computed tomography scan of the neck identified a communicating tract between the lumen of the cystic mass and mid-trachea. The foal was systemically healthy at this initial presentation, and delayed removal of the cyst was recommended to allow further maturation of the foal prior to undergoing general anaesthesia. Upon discharge, the cyst continued to grow in size and became more fluid than air-filled requiring repeat centesis and draining. The foal was then re-presented at 3 weeks of age for surgical removal. In surgery, direct communication with the trachea was identified and ligated. Histopathology demonstrated that the cyst lining was composed of squamous epithelium with goblet cells and occasional ciliated cells. The location, morphological features and congenital presentation of the mass were consistent with a paratracheal air cyst (PAC). Surgical resection resulted in excellent functional and cosmetic outcome. Although not previously reported in horses, PAC should be included in the differential diagnosis of an air-filled ventral neck mass in equine neonates. Complete surgical excision may result in a successful outcome. 相似文献
65.
We measured vertical and horizontal variation in canopy transmittance of photosynthetically active radiation in five Pseudotsuga menziesii (Mirb.) Franco-Tsuga heterophylla (Raf.) Sarg. (Douglas-fir-western hemlock) stands in the central Cascades of southern Washington to determine how stand structure and age affect the forest light environment. The shape of the mean transmittance profile was related to stand height, but height of mean maximum transmittance was progressively lower than maximum tree height in older stands. The vertical rate of attenuation declined with stand age in both the overstory and understory. A classification of vertical light zones based on the mean and variance of transmittance showed a progressive widening of the bright (low variance and high mean) and transition (high variance and rapid vertical change) zones in older stands, whereas the dim zone (low variance and mean) narrowed. The zone of maximum canopy surface area in height profiles, estimated by inversion of transmittance profiles, changed from relatively high in the canopy in most young stands ("top-heavy") to lower in the canopy in older stands ("bottom-heavy"). In the understory, all stands had similar mean transmittances, but the spatial scale of variation increased with stand age and increasing crown size. The angular distribution of openness was similar in all stands, though the older stands were less open at all angles than the younger stands. Understory openness was generally unrelated to transmittance in the canopy above. Whole-canopy leaf area indices, estimated using three methods of inverting light measurements, showed little correspondence across methods. The observed patterns in light environment are consistent with structural changes occurring during stand development, particularly the diversification of crowns, the creation of openings of various sizes and the elaboration of the outer canopy surface. The ensemble of measurements has potential use in distinguishing forests of differing ages that have similar stature. 相似文献
66.
Tissue DT Lewis JD Wullschleger SD Amthor JS Griffin KL Anderson OR 《Tree physiology》2002,22(15-16):1157-1166
Trees exposed to elevated CO2 partial pressure ([CO2]) generally show increased rates of photosynthesis and growth, but effects on leaf respiration are more variable. The causes of this variable response are unresolved. We grew 12-year-old sweetgum trees (Liquidambar styraciflua L.) in a Free-Air CO2 Enrichment (FACE) facility in ambient [CO2] (37/44 Pa daytime/nighttime) and elevated [CO2] (57/65 Pa daytime/nighttime) in native soil at Oak Ridge National Environmental Research Park. Nighttime respiration (R(N)) was measured on leaves in the upper and lower canopy in the second (1999) and third (2000) growing seasons of CO2 fumigation. Leaf respiration in the light (R(L)) was estimated by the technique of Brooks and Farquhar (1985) in the upper canopy during the third growing season. There were no significant short-term effects of elevated [CO2] on R(N) or long-term effects on R(N) or R(L), when expressed on an area, mass or nitrogen (N) basis. Upper-canopy leaves had 54% higher R(N) (area basis) than lower-canopy leaves, but this relationship was unaffected by CO2 growth treatment. In August 2000, R(L) was about 40% of R(N) in the upper canopy. Elevated [CO(2)] significantly increased the number of leaf mitochondria (62%), leaf mass per unit area (LMA; 9%), and leaf starch (31%) compared with leaves in ambient [CO(2)]. Upper-canopy leaves had a significantly higher number of mitochondria (73%), N (53%), LMA (38%), sugar (117%) and starch (23%) than lower-canopy leaves. Growth in elevated [CO2] did not affect the relationships (i.e., intercept and slope) between R(N) and the measured leaf characteristics. Although no factor explained more than 45% of the variation in R(N), leaf N and LMA were the best predictors for R(N). Therefore, the response of RN to CO2 treatment and canopy position was largely dependent on the magnitude of the effect of elevated [CO2] or canopy position on these characteristics. Because elevated [CO2] had little or no effect on N or LMA, there was no effect on R(N). Canopy position had large effects on these leaf characteristics, however, such that upper-canopy leaves exhibited higher R(N) than lower-canopy leaves. We conclude that elevated [CO2] does not directly impact leaf respiration in sweetgum and that barring changes in leaf nitrogen or leaf chemical composition, long-term effects of elevated [CO2] on respiration in this species will be minimal. 相似文献
67.
Evaluation of existing on-farm agroforestry plots should provide useful supplementary information for the design of improved agroforestry systems, in both research and development projects. Such evaluation has been little used, however, largely due to the methodological difficulties of surveying highly variable on-farm plots, and difficulties in identifying key variables for measurement. This paper describes a set of methods and tools used in evaluating plots of alley-cropping and tree borders around crop fields established by farmers working with the CARE Agroforestry Extension Project in western Kenya. Details of survey design, sampling, and implementation are discussed, and suggestions made for carrying out agroforestry surveys in other projects. A condensed version of the questionnaire is appended. 相似文献
68.
A NMR study of water distribution in hardwoods at several equilibrium moisture contents 总被引:1,自引:0,他引:1
The water state of one tropical (Robinia coccinea) and two temperate (Acer saccharum and Fagus grandifolia) hardwoods was determined at different equilibrium moisture contents (EMC) during desorption at 25°C. NMR technique was used
to separate different components of water in wood. The species studied presented different structures, which were apparent
on the spin–spin relaxation T2 values. Three different water components were separated: slow T2 (liquid water in vessel elements), medium T2 (liquid water in fiber and parenchyma elements) and fast T2 (bound or cell wall water). The NMR results showed that even at equilibrated conditions a region exists where loss of liquid
water and bound water takes place simultaneously. This region will vary according to the wood structure. Finally, liquid water
was present at EMC lower than the fiber saturation point, which contradicts the concept of this point when considered as a
bulk property of wood. 相似文献
69.
Sanding is a common practice required in order to prepare wood surfaces for coating. Little literature is available regarding the effect of sanding parameters on the quality of surfaces. Sugar maple wood surfaces were evaluated in samples that had been sanded using two types of abrasive minerals, three grit sizes and four feed speeds. Roughness, wetting properties and cell damage were used to assess surface quality. Both abrasives decreased roughness and cell damage from 100- to 120-grit sanding stage. Addition of a 150-grit stage did not further reduce the roughness, whereas the cell damage continued to decrease. Increasing feed speed led to rougher surfaces due to higher fibrillation. Surfaces produced by silicon carbide were smoother and less damaged than those obtained with aluminum oxide. However, the surfaces sanded with aluminum oxide were more wettable and showed no significant difference in wetting time as a function of grit size. For these surfaces, the wetting time was reduced as feed speed increased.An erratum to this article is available at .An erratum to this article can be found at 相似文献
70.
Within-leaf variations in cell size, mitochondrial numbers and dark respiration rates were compared in the most recently expanded tip, the mid-section and base of needles of Pinus radiata D. Don trees grown for 4 years in open-top chambers at ambient (36 Pa) or elevated (65 Pa) carbon dioxide partial pressure (p(CO2)a). Mitochondrial numbers and respiratory activity varied along the length of the needle, with the highest number of mitochondria per unit cytoplasm and the highest rate of respiration per unit leaf area at the base of the needle. Regardless of the location of the cells (tip, middle or basal sections), needles collected from trees grown in elevated p(CO2)a had nearly twice the number of mitochondria per unit cytoplasm as those grown in ambient p(CO2)a. This stimulation of mitochondrial density by growth at elevated p(CO2)a was greater at the tip of the needle (2.7 times more mitochondria than in needles grown in ambient CO2) than at the base of the needle (1.7 times). The mean size of individual mitochondria was unaffected either by growth at elevated p(CO2)a or by position along the needle. Tree growth at elevated p(CO2)a had a variable effect on respiration per unit leaf area, significantly increasing respiration in the tip of the needles (+25%) and decreasing respiration at the mid-section and base of the needles (-14% and -25%, respectively). Although a simple relationship between respiration per unit leaf area and mitochondrial number per unit cytoplasm was found within each CO2 treatment, the variable effect of growth at elevated p(CO2)a on respiration along the length of the needles indicates that a more complex relationship must determine the association between structure and function in these needles. 相似文献