Growth response of six weed species and spring barley (Hordeum vulgare) to increasing levels of nitrogen and phosphorus   总被引：1，自引：0，他引：1  

C ANDREASEN  A-S LITZ  & JC STREIBIG 《Weed Research》2006,46(6):503-512

A glasshouse experiment was carried out to investigate the influence of increasing levels of nitrogen and phosphorus on the growth of six common weed species growing alone or in competition with spring barley (Hordeum vulgare). Capsella bursa‐pastoris, Chenopodium album, Papaver rhoeas, Sinapis arvensis, Spergula arvensis, Viola arvensis and spring barley were grown in pots with different levels of nitrogen (0, 30, 60, 90, 120 and 150 kg N ha^?1) or phosphorus (0, 10, 20, 30, 40 and 60 kg P ha^?1). The aboveground parts of the plants were harvested after 7 weeks and the dry weight of shoots, percentage N and P content of the shoot and uptake of N and P were determined. A linear or a polynomial model was used to describe the data. Growing alone, Spergula arvensis was the only weed species that increased its dry weight at the same rate as barley. Weed species with low dry weight increase had larger increases in percentage N or P content than barley, indicating a luxury accumulation of nutrients. The uptake of N and P per pot did not differ much between weeds and barley. V. arvensis and P. rhoeas accumulated least nutrients (per cent of dry matter) and Spergula arvensis accumulated most. Weeds grew poorly in competition with barley. The percentage N and P content in barley did not change when they grew in competition with weeds.  相似文献   

Characteristics for a judgment of the sorption and swelling behavior of wood   总被引：1，自引：1，他引：1  

D. Noack  E. Schwab  A. Bartz 《Wood Science and Technology》1973,7(3):218-236

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Suppression of bacterial soft rot in potato tubers by application of kasugamycin     

Jerry A. Bartz 《American Journal of Potato Research》1999,76(3):127-136

An immersion in aqueous solutions of Kasumin®, containing kasugamycin at 10 to 320 mg/L (ppm) for 1 to 320 sec delayed or prevented the development of soft rot on inoculated (Erwinia carotovora subsp.carotovora) tuber disks incubated over wet filter paper at 24C for 24 to 72 hr. Treatment efficacy decreased as inoculum level and incubation period increased. Short immersion periods were not as effective as longer ones. When stored tubers were inoculated withE. c. carotovora and incubated up to 5 days in fog chamber at 20 C, immersion treatments in 20 to 400 ppm kasugamycin either had no effect or increased soft rot development. By contrast, when the stored tubers were cut into sections before inoculation and treatment, immersion in 300 ppm reduced soft rot development on the cut surfaces from 83% (inoculated controls) to 3.2%. With non-inoculated sections, treatment with 25 ppm reduced the SAD from 13.3 to 0.6%. Wash or rinse treatment of freshly harvested tubers in 40 to 160 ppm produced a significant reduction in the severity of bacterial soft rot among tubers incubated for 72 to 96-hr. The 160-ppm treatment delayed disease onset by at least 24 hr. Pre-washing freshly harvested tubers with clean or chlorinated water prior to antibiotic treatment did not consistently improve the efficacy of the kasugamycin treatment.  相似文献   

Vertical Flux of Biogenic Carbon in the Ocean: Is There Food Web Control?     

RB Rivkin  L Legendre  D Deibel  JE Tremblay  B Klein  K Crocker  S Roy  N Silverberg  C Lovejoy  F Mesple  N Romero  MR Anderson  P Matthews  C Savenkoff  A Vezina  JC Therriault  J Wesson  C Berube  RG Ingram 《Science (New York, N.Y.)》1996,272(5265):1163-1166

Models of biogenic carbon (BC) flux assume that short herbivorous food chains lead to high export, whereas complex microbial or omnivorous food webs lead to recycling and low export, and that export of BC from the euphotic zone equals new production (NP). In the Gulf of St. Lawrence, particulate organic carbon fluxes were similar during the spring phytoplankton bloom, when herbivory dominated, and during nonbloom conditions, when microbial and omnivorous food webs dominated. In contrast, NP was 1.2 to 161 times greater during the bloom than after it. Thus, neither food web structure nor NP can predict the magnitude or patterns of BC export, particularly on time scales over which the ocean is in nonequilibrium conditions.  相似文献   

Simultaneous Measurement of Local Gain and Electron Density in X-ray Lasers     

R Cauble  Da Silva LB  TW Barbee  P Celliers  C Decker  RA London  JC Moreno  JE Trebes  AS Wan  F Weber 《Science (New York, N.Y.)》1996,273(5278):1093-1096

X-ray lasers (XRLs) have experimental average gains that are significantly less than calculated values and a persistently low level of spatial coherence. An XRL has been used both as an injected signal to a short XRL amplifier and as an interferometer beam to measure two-dimensional local gain and density profiles of the XRL plasma with a resolution near 1 micrometer. The measured local gain is in agreement with atomic models but is unexpectedly spatially inhomogeneous. This inhomogeneity is responsible for the low level of spatial coherence observed and helps explain the disparity between observed and simulated gains.  相似文献   

栽培稻分类方法的比较   总被引：18，自引：3，他引：18  

周汇  JC Glaszmann  程侃声  施晓群 《中国水稻科学》1988,2(1):1-7

 为了比较Glaszmann和程侃声等对亚洲栽培稻的分类体系,将Glaszmann氏提供的197个水稻品种的同功酶位点原始记录和程氏对它们就6个形态性状的评分作了主成分分析和聚类分析。结果显示二人的分类基本一致,数值分类也表明栽培稻可以只分籼粳两个亚种,处于中间的少数品种可称为偏籼或偏粳。程氏采用的“性状指数法”似更为便利而有效,特别适于田间及育种工作,虽然带有一定的经验成分,但加以生化或数值分类的检验,即可弥补该法的不足,有助于澄清个别不够明确和错划的事例。因此,我们建议为求得最佳的分类系统,最好运用二种以上的方法,相互补充校正。  相似文献   

Age-related differences in collagen crimp patterns in the superficial digital flexor tendon core region of untrained horses   总被引：5，自引：0，他引：5  

JC PATTERSON-KANE  EC FIRTH  AE GOODSHIP  DAD PARRY 《Australian veterinary journal》1997,75(1):39-44

Objective To measure collagen fibril crimp angles and lengths as well as collagen fibril mass-average diameters in central and peripheral regions of the superficial digital flexor tendon of wild horses, to ascertain any age-related changes in either region in the absence of imposed galloping exercise.
Design Measurements from a random cull of wild horses.
Sample population Superficial digital flexor tendon samples were taken from 23 wild horses ranging in age from two to ten years.
Procedure Horses were divided into 'young' (< 5 years, n = 10), 'middle-aged' (5 to < 10 years, n = 9) and 'old' groups (10+ years, n = 4) and the mean crimp angle, mean crimp length and collagen fibril mass-average diameter calculated for the central region, and for the peripheral region of each group. Differences between groups and regions were analysed using two-tailed t tests.
Results The crimp angle for the central region was found to decrease with age, so that in old horses it was smaller than that for the tendon periphery (P < 0.05). The crimp angle for the latter region did not alter significantly with age. Crimp period lengths and collagen fibril mass-average diameters did not show significant changes with age in either region.
Conclusion Reduction of the crimp angle in the core of the superficial digital flexor tendon occurs normally with age, as tendons of older animals would have undergone a higher number of loading cycles. It is possible that athletic training increases the frequency and/or the magnitude of high loading cycles experienced by the tendon, and may accelerate and worsen the normal load-related ageing process in the superficial digital flexor tendons of young performance horses, particularly in the central regions where lesions usually occur.  相似文献   

Fasciola hepatica infection in farmed emus (Dromaius novaehollandiae)     

JL VAUGHAN  JA CHARLES  JC BORAY 《Australian veterinary journal》1997,75(11):811-813

Objective To describe two cases of infection with Fasciola hepatica i n young farmed emus, subacute and chronic fasci-olosis and a response to treatment of the flock with albenda-zole.
Procedure Gross lesions were found at necropsy and hepatic lesions in microscopic examination. The parasite recovered from one emu was identified by its morphological characteristics and an egg count reduction test was carried out after treatment of the flock with albendazole.
Results Hepatic lesions resembling subacute and chronic fasciolosis of ruminants were identified. An adult fluke was recovered from the liver of one of the birds and was identified as F hepatica . The eggs of the fluke were irregular in shape and size. No fluke eggs were identifiable in faeces of live emus 10 days after treatment of the flock with albendazole at a dose of 10 mg/kg.
Conclusions This is the first reported case of infection with F hepatica i n farmed emus and the first report of the occurrence of Fasciola infection is the class Aves. The irregular shape and size of the eggs may be attributable to infection of an aberrant host. Treatment with albendazole eliminated eggs from the faeces of the flock.  相似文献   

Verotoxin-producing Escherichia coli from the faeces of sheep, calves and pigs   总被引：4，自引：0，他引：4  

H. SIDJABAT-TAMBUNAN  JC BENSINK 《Australian veterinary journal》1997,75(4):292-293

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Closantel resistance in Huemonchus contortus from sheep     

PF ROLFE  JC BORAY  C. FITZGIBBON  G. PARSONS  P. KEMSLEY  N. SANGSTER 《Australian veterinary journal》1990,67(1):29-31

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