水曲柳的光合作用效率   总被引：4，自引：0，他引：4  

桑运荣  王传宽  郎广林  周晓峰  赵惠勋 《东北林业大学学报》1999,27(2):15-18

在野外自然环境条件下对水曲柳叶片的光合效率（ＰＥ）及其相关的环境因子的测定结果表明：水曲柳的光合效率随叶片生长发育而升高,旺盛生长的叶片光合效率低于成年叶和老叶;生长末期老叶的光合效率高达５．８９％,在影响水曲柳光合效率的环境因子中,ＰＥ随光合有效辐射（Ｑ）的增大而呈现幂函数式下降;ＰＥ与水汽压亏缺（ＶＰＤ）成负相关,而与ＣＯ２浓度（包括周围空气中的ＣＯ２浓度（Ｃａ）和细胞间隙的ＣＯ２浓度（Ｃｉ）  相似文献   

微机在全光雾插嫩枝育苗上应用的研究     

安建强  姜磊  黄志辉  桑士舟  李树卿 《农业网络信息》2002,17(5):8-10

本文介绍了微型计算机的测控技术在农业育苗方面的一个应用。通过监测温度、湿度、光照等环境参量,控制执行机构营造嫩枝生长所需的小环境;同时利用计算机的多任务执行系统实现对多个苗盘的控制,从而达到自动化、工厂化育苗的目的。  相似文献   

Peritoneography and Herniography in Non-Human Primates     

Mitchell  Bush RichardM.  Heller  Jr.  Clinton W.  Gray  Kook Sang  Oh  A. Everette  James  Jr. 《Veterinary radiology & ultrasound》1974,15(2):77-82

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Predicting mortality of phosphine-resistant adults of Sitophilus oryzae (L) (Coleoptera: Curculionidae) in relation to changing phosphine concentration     

Daglish GJ  Kopittke RA  Cameron MC  Pavic H 《Pest management science》2004,60(7):655-659

Adults of a phosphine-resistant strain of Sitophilus oryzae (L) were exposed to constant phosphine concentrations of 0.0035-0.9mg litre(-1) for periods of between 20 and 168h at 25 degrees C, and the effects of time and concentration on mortality were quantified. Adults were also exposed to a series of treatments lasting 48, 72 or 168 h at 25 degrees C, during which the concentration of phosphine was varied. The aim of this study was to determine whether equations from experiments using constant concentrations could be used to predict the efficacy of changing phosphine concentrations against adults of S oryzae. A probit plane without interaction, in which the logarithms of time (t) and concentration (C) were variables, described the effects of concentration and time on mortality in experiments with constant concentrations. A derived equation of the form C(n)t = k gave excellent predictions of toxicity when applied to data from changing concentration experiments. The results suggest that for resistant S oryzae adults there is nothing inherently different between constant and changing concentration regimes, and that data collected from fixed concentrations can be used to develop equations for predicting mortality in fumigations in which phosphine concentration changes. This approach could simplify the prediction of efficacy of typical fumigations in which concentrations tend to rise and then fall over a period of days.  相似文献   

Development of goat embryos reconstituted with somatic cells: the effect of cell-cycle coordination between transferred nucleus and recipient oocytes     

Zhang LS  Jiang MX  Lei ZL  Li RC  Sang D  Sun QY  Chen DY 《The Journal of reproduction and development》2004,50(6):661-666

The developmental ability and the nucleus and microtubule dynamics of nuclear transplanted goat embryos derived from in vitro matured oocytes were studied while controlling cell-cycle coordination of donor embryonic nuclei and recipient cytoplasts. Three groups of transfers were studied: G0/G1 (after the fibroblast cells grew to 100% confluence) and G2/M (nocodazole treated) phase fibroblasts transferred to MII cytoplasts (G0/G1-->MII and G2/M-->MII group, respectively), and G0/G1 phase fibroblasts transferred to preactivated cytoplasts, mostly at S-phase, (G0/G1-->Pre group) by electrical fusion. The results showed that fusion and developmental ability did not differ between G0/G1-->MII and G0/G1-->Pre groups. However the developmental rate of embryos in the G0/G1-->MII group was significantly higher than that of the G2/M-->MII group. Most fibroblast nuclei (G0/G1 and G2/M) transferred into MII oocytes underwent premature chromosome condensation (PCC). Normal spindle were only detected in the G0/G1-->MII group. In contract, fibroblast nuclei in pre-activated oocytes rarely underwent PCC, but formed a swollen nuclear structure. The data suggest that in vitro matured goat oocytes can support the development of somatic fibroblasts after nuclear transfer, G0/G1 -->MII and G0/G1-->S nuclear transfer might be effective ways for improving the developmental competence of the reconstituted embryos, and that G2/M-->MII nuclear transfer by electrical fusion (even in Ca2+-free fusion medium) induces abnormal chromosome ploidy.  相似文献   

Longitudinal study to investigate variation in results of repeated ELISA and culture of fecal samples for Mycobacterium avium subsp paratuberculosis in commercial dairy herds     

van Schaik G  Rossiter CR  Stehman SM  Shin SJ  Schukken YH 《American journal of veterinary research》2003,64(4):479-484

OBJECTIVE: To determine sources and amounts of variation in a kinetics ELISA (KELA) and results of culture of fecal samples for Mycobacterium avium subsp paratuberculosis (MAP) in repeated tests of individual cows. ANIMALS: 112 cows on 6 commercial dairy farms in New York. PROCEDURE: A nonrandom longitudinal study was conducted from January 2001 to March 2002. A KELA was performed monthly, and MAP culture was performed bimonthly. Cow- and herd-level data were collected. The KELA and culture results were analyzed by use of models that corrected for clustering within herds and repeated measures on cows. RESULTS: Cows of second or higher lactation had increased KELA values, compared with values for first-lactation cows. Cows had lowest KELA values during the first 15 days in milk; KELA values increased until 60 days in milk and then stabilized. Moderate and heavy shedders had significantly higher KELA values than culture-negative cows, and KELA values of shedders progressively increased over time. On average, the KELA value was significantly increased 132 days after a cow was first detected to be a moderate shedder and 236 days after a cow was first detected to be a low shedder. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis suggests that KELA results vary on a cow-level on the basis of lactation number and stage of lactation. High KELA values indicate heavy fecal shedding, but the KELA is not useful in identifying low and moderate shedders that can require up to 236 days to have a significant increase in KELA value.  相似文献   

Antibody-based bio-nanotube membranes for enantiomeric drug separations   总被引：1，自引：0，他引：1  

Lee SB  Mitchell DT  Trofin L  Nevanen TK  Söderlund H  Martin CR 《Science (New York, N.Y.)》2002,296(5576):2198-2200

Synthetic bio-nanotube membranes were developed and used to separate two enantiomers of a chiral drug. These membranes are based on alumina films that have cylindrical pores with monodisperse nanoscopic diameters (for example, 20 nanometers). Silica nanotubes were chemically synthesized within the pores of these films, and an antibody that selectively binds one of the enantiomers of the drug was attached to the inner walls of the silica nanotubes. These membranes selectively transport the enantiomer that specifically binds to the antibody, relative to the enantiomer that has lower affinity for the antibody. The solvent dimethyl sulfoxide was used to tune the antibody binding affinity. The enantiomeric selectivity coefficient increases as the inside diameter of the silica nanotubes decreases.  相似文献   

榆童锤角叶蜂防治指标的研究     

武星煜  高嵩 《甘肃林业科技》2001,26(4):16-18

通过研究榆童锤角叶蜂幼虫期的食量，叶量损失对直径0．4－0．6cm、长50cm标准枝生长量的影响，建立标准枝叶损失率与标准枝生长量损失率的生长曲线，分析确定出明显影响标准枝材积生长量的叶损失临界值，即叶损失率达45％时，为防治指标所允许的叶损失阈值。  相似文献   

Performance and blood plasma amino acid and urea concentrations in growing pigs given diets of cereals and groundnut meal and supplemented with graded amounts of L-lysine     

R. Braude  Rosemary J. Fulford  K.G. Mitchell  A.W. Myres  J.W.G. Porter 《Livestock Production Science》1974,1(4):383-400

The addition of graded amounts of L-lysine to a basal diet of cereals and groundnut meal given to growing pigs caused the expected improvements in rate of growth, N retention and carcass quality. Best responses were obtained when the diet contained 9 g lysine/kg; above that level there were no significant additional responses.Blood samples were taken from the anterior vena cava before and at intervals after a meal of each diet, and the concentration of amino acids and urea in the plasma determined. The concentrations of most amino acids in blood plasma increased after a meal, reaching maxima about 2 h after feeding.At all times of sampling the concentrations in plasma of essential amino acids other than lysine were largely unaffected by the lysine content of the diet, but the concentration of lysine increased linearly over a wide range of lysine intake.The concentration of urea in blood plasma fell as the lysine content of the diet increased. Lowest concentrations were found with diets containing 9 g or more lysine/kg.It was concluded that measurement of the concentrations of urea in blood plasma of growing pigs fed twice daily may be of more value in assessing the amino acid requirements and efficiency of protein utilization than determination of changes in concentration of blood plasma amino acids.  相似文献   

不同养分进食水平及日粮降解蛋白质与代谢能比对妊娠后期细毛羊生产性能的影响     

李建国  桑润滋  曹玉凤  郭钢  孔祥浩  王俊杰 《动物营养学报》1996,(2)

用87只2～3岁的河北细毛羊母羊,对日粮不同代谢能(ME)、降解蛋白(RDP)和非降解蛋白(UDP)水平对妊娠后期母羊体重及羔羊初生重影响进行了研究。试验结果表明,河北细毛羊妊娠后期(100～150天)能量和蛋白质的适宜供给量分别是0.79MJME/kgW~(0.75)/d、7.02gRDP/kgW~(0.75)/d和2.32gUDP/kgW~(0.75)/d。这一营养水平可保证母羊体重适度增加。同时还发现母羊日粮能量及蛋白质水平对羔羊初生重无显著影响。  相似文献