Growth response of six weed species and spring barley (Hordeum vulgare) to increasing levels of nitrogen and phosphorus

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.     

Investigation of bovine haemoplasmas and their association with anaemia in New Zealand cattle

CASE HISTORY AND CLINICAL FINDINGS: A dairy cow, from a herd in the Waikato region of New Zealand, was reported with regenerative anaemia on 12 September 2014. Testing of blood from the animal using PCR assays for Theileria orientalis produced a negative result for both Chitose and Ikeda types.

LABORATORY FINDINGS: Using PCR and DNA sequencing, blood from the cow was positive for Candidatus Mycoplasma haemobos. Further testing of another 12 animals from the case herd, 27 days after the affected cow was first reported, showed 11 animals were positive for Candidatus M. haemobos or Mycoplasma wenyonii in the PCR. None of these cattle were clinically anaemic or positive for T. orientalis Ikeda type using PCR.

A convenience sample of 47 blood samples from cattle throughout New Zealand, submitted to the Investigation and Diagnostic Centre (Ministry for Primary Industries) for surveillance testing for T. orientalis Ikeda, was selected for further testing for bovine haemoplasmas. Of these samples, 6/47 (13%) and 13/47(28%) were positive for M. wenyonii and Candidatus M. haemobos, respectively. There was no difference in the proportion of samples positive for the bovine haemaplasmas between cattle with anaemia that were negative for T. orientalis (6/20, 33%), or without anaemia or T. orientalis (10/18, 56%), or from cattle herds experiencing anaemia and infection with T. orientalis Ikeda type (3/9, 33%).

DIAGNOSIS: Bovine haemoplasmosis.

CLINICAL RELEVANCE: The presence of bovine haemoplasmas in blood does not establish causality for anaemia in cattle. Diagnosis of anaemia associated with haemoplasmosis would require exclusion of other causes of regenerative anaemia and an association of the agent with anaemia in affected cattle herds. The data collected in this study did not provide evidence that bovine haemoplasmas were associated with a large number of outbreaks of anaemia in cattle in New Zealand.     

Resynchronising returns to service in anoestrous dairy cows in the South Island of New Zealand

AIMS: To investigate the effect of targeted resynchronisation of cows treated for non-observed oestrus before the planned start of mating (PSM), that were not detected in oestrus or pregnant 23 days after treatment (phantom cows), on the proportion pregnant at 42 days after PSM and the end of mating.

METHODS: Farm staff from eight herds in two regions of the South Island of New Zealand identified 1,819 cows not showing oestrus by 10 days before PSM. These cows were treated with intravaginal progesterone for 7 days, and I/M gonadorelin 10 days and 1 day before PSM. Three days before PSM they were injected with cloprostenol and equine chorionic gonadotrophin, with fixed time artificial insemination (FTAI) at PSM. By 23 days after PSM, 1,218 cows had not returned to oestrus. Of these, 161 cows confirmed not pregnant by transrectal ultrasonography were randomly assigned to no treatment (control group; n=74) or were resynchronised 25 days after PSM using the same treatment programme as above, with FTAI 35 days after PSM (n=87). All cows that returned to oestrus were artificially inseminated until 42 days after PSM, when natural mating was used. All cows were examined using transrectal ultrasonography 80 to 90 days after PSM to confirm conception dates.

RESULTS: Of the 1,819 anoestrous cows treated before PSM, 526 (29 (95% CI=23.1–34.0)%) had not been observed in oestrus by 23 days after PSM and had not conceived, so were diagnosed as phantoms cows. For resynchronised cows, 42/87 (48 (95% CI=37.8–58.8)%) were pregnant by 42 days after PSM compared to 21/74 (28 (95% CI=18.1–38.7)%) control cows (p=0.009). At the end of mating 58/87 (67 (95% CI=56.6–76.7)%) cows in the resynchronised group were pregnant and 46/74 (62 (95% CI=50.9–73.2)%) in the control group (p=0.554). The hazard of conception from 21 to 42 days after PSM was 1.9 (95% CI=1.07–3.12) times greater for resynchronised than control cows (p=0.026).

CONCLUSION: In cows not observed in oestrus and treated before PSM, resynchronisation increased the proportion pregnant by 42 days after PSM.

CLINICAL RELEVANCE: The benefit of resynchronisation depends on the number of anoestrous cows before PSM and the number of phantom cows after PSM. However at the herd-level it is likely that providing advice to reduce the known risk factors for cows not being observed in oestrus before the PSM may well be more cost effective than identifying and treating a sub-population of phantom cows.     

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

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.     

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

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.     

栽培稻分类方法的比较

 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。     

Age-related differences in collagen crimp patterns in the superficial digital flexor tendon core region of untrained horses

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.