Influence of ambient light and temperature on laser-induced chlorophyll fluorescence measurements

Chlorophyll fluorescence analysis is a powerful tool for the study of spatial and temporal heterogeneities of photosynthetic performance and has been successfully used at the laboratory scale. Field applications, however, are confronted with the challenges presented by fluctuating environmental factors, particularly varying light and temperature conditions.The influence of ambient light and temperature on the measurement signal of the laser-induced two-wavelength chlorophyll fluorescence remains both controversially and largely not well understood. Yet, a thorough understanding of this issue is essential for exploiting the large potential of this measurement method for precision agriculture as well as for precision phenotyping in plant breeding where the influence of ambient light and temperature is inevitably present. To fill this gap in our knowledge, we therefore investigated this area under both field and controlled laboratory conditions.Field measurements of laser-induced two-wavelength chlorophyll fluorescence under variable light conditions show a linear influence of direct sunlight on the ratio of F₆₉₀/F₇₃₀, whereas the ratio is unchanged under diffuse sunlight.We describe these measurement results in terms of a physical model of light–matter interaction in plant leaves. In particular, the results appear to derive from energetic saturation effects of the upper plant layers induced by sunlight, which result in larger mean depths of fluorescence emission induced by additional exciting light (i.e. laser light), in connection with the different scattering properties of the two different fluorescence light wavelengths (690 nm and 730 nm) on their way to the surface. The same model also provides an explanation for the temperature dependence of the fluorescence intensity ratio and is well suited to deal with the effects of both variable light and temperature conditions under field conditions.     

Performance of nitrification inhibitors with different nitrogen fertilizers and soil textures

Nitrification inhibitors (NIs), DCD (dicyandiamide), and DMPP (3,4‐dimethylpyrazole phosphate), in combination with urea (UR) and ammonium sulfate nitrate (ASN) fertilizers were studied under contrasting soil textures (sand, loam, and clay) from cultivated soils collected in Brazil and Germany. Soil samples were incubated over 50 days and the content of ammonium ( ), nitrate ( ), and soil pH were measured periodically. Applied NIs delayed the nitrification process across all soil textures. Correlation analysis indicated that combining ASN with NIs resulted in higher content and efficiency in delaying the nitrification process with high N‐conversion rate (r = –0.82). The combination of ASN+ DMPP increased the efficiency of the N‐conversion rate (r = –0.86) due to H⁺ release in soil, while UR+DCD (r = –0.50) had an efficiency of the N‐conversion rate similar to UR (r = –0.42). All the NIs had a better performance in reducing formation in sandy soils as compared to the loam and clay textured soils. Use of DMPP with an N fertilizer results in a soil pH decrease and can be an option to increase the efficiency of the N‐conversion rate, reducing N losses in soil. Overall, our results suggest that NIs have a better performance in reducing formation in sandy soils as compared to that of the loam and clay textured soils. Use of DMPP with ASN results in a soil pH decrease and can be an option to reduce N losses in soil.     

Optimizing the size of the area surveyed for monitoring a Eurasian lynx (Lynx lynx) population in the Swiss Alps by means of photographic capture–recapture

We studied the influence of surveyed area size on density estimates by means of camera‐trapping in a low‐density felid population (1–2 individuals/100 km²). We applied non‐spatial capture–recapture (CR) and spatial CR (SCR) models for Eurasian lynx during winter 2005/2006 in the northwestern Swiss Alps by sampling an area divided into 5 nested plots ranging from 65 to 760 km². CR model density estimates (95% CI) for models M₀ and M_h decreased from 2.61 (1.55–3.68) and 3.6 (1.62–5.57) independent lynx/100 km², respectively, in the smallest to 1.20 (1.04–1.35) and 1.26 (0.89–1.63) independent lynx/100 km², respectively, in the largest area surveyed. SCR model density estimates also decreased with increasing sampling area but not significantly. High individual range overlaps in relatively small areas (the edge effect) is the most plausible reason for this positive bias in the CR models. Our results confirm that SCR models are much more robust to changes in trap array size than CR models, thus avoiding overestimation of density in smaller areas. However, when a study is concerned with monitoring population changes, large spatial efforts (area surveyed ≥760 km²) are required to obtain reliable and precise density estimates with these population densities and recapture rates.     

禾谷缢管蚜在越冬寄主植物上的行为研究

通过室内饲养观察、田间调查和利用微型昆虫显微摄影技术,研究了禾谷缢管蚜越冬卵在越冬寄主稠李(Prunus padis)上孵化,干母、干雌取食、生长发育和繁殖等行为过程,以及形态和体色变异特点。结果表明,禾谷缢管蚜越冬卵在室内的孵化率为88.68％-92.51％;在德国北部吕贝克附近田间孵化率为24.2％。越冬卵孵化起点温度低于4℃。在室温22℃下卵孵化历期为5-7d,孵化高峰在卵孵化始期后第3-4天。一日内最佳孵化时间在05:00-07:30。在室内饲养条件下,将越冬卵孵化的干母直接移植到麦苗上,蚜虫几乎都不能存活。     

Prevalence of DNA of Mycoplasma haemofelis, 'Candidatus Mycoplasma haemominutum,' Anaplasma phagocytophilum, and species of Bartonella, Neorickettsia, and Ehrlichia in cats used as blood donors in the United States

OBJECTIVE: To identify the prevalence of DNA of Mycoplasma haemofelis; 'Candidatus Mycoplasma haemominutum'; Anaplasma phagocytophilum; and species of Bartonella, Neorickettsia, and Ehrlichia in blood of cats used as blood donors in the United States. DESIGN: Prospective study. ANIMALS: 146 cats that were active blood donors. PROCEDURES: Environmental history was requested for each blood-donor cat from which a blood sample (mixed with EDTA) was available. Polymerase chain reaction assays capable of amplifying the DNA of the microorganisms of interest following DNA extraction from blood were performed. RESULTS: Overall, DNA of one or more of the infectious agents was detected in blood samples from 16 of 146 (11%) feline blood donors. Twenty-eight laboratory-reared cats housed in a teaching hospital had negative results for DNA of all organisms investigated. The DNA of at least 1 infectious agent was amplified from blood samples collected from 16 of 118 (13.6%) community-source cats; assay results were positive for 'Candidatus M haemominutum,' M haemofelis, or Bartonella henselae alone or in various combinations. Of the community-source cats allowed outdoors (n = 61) or with known flea exposure (44), DNA for a hemoplasma or B henselae was detected in 21.3% and 22.7%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: When community-source cats, cats allowed outdoors, or cats exposed to fleas are to be used as blood donors, they should be regularly assessed for infection with M haemofelis, 'Candidatus M haemominutum,' and Bartonella spp, and flea-control treatment should be regularly provided.     

Treatment of severe adverse cutaneous drug reactions with human intravenous immunoglobulin in two dogs

Severe adverse cutaneous reactions were documented in two dogs with acute skin lesions and systemic signs after exposure to several oral and injectable drugs. Because of the high morbidity and mortality rates of many severe cutaneous drug reactions and a poor response to supportive care, wound management, and conventional immunosuppressive therapy, human intravenous immunoglobulin (IVIG) was infused on 2 consecutive days (1 g/kg per day) after informed consent was received. Human IVIG, with supportive care, resulted in rapid resolution of dermatological and systemic signs in both dogs; this treatment may be considered in other cases of severe cutaneous drug reactions.     

Hemolysis,myopathy, and cardiac disease associated with hereditary phosphofructokinase deficiency in two Whippets

Abstract: Two male castrated Whippet littermates were presented at 1 year of age for pallor, tachycardia, systolic heart murmur, dark yellow to orange feces, intermittent lethargy, pigmenturia, and muscle shivering or cramping after exercise. Persistent macrocytic hypochromic anemia with marked reticulocytosis and metarubricytosis was found when CBC results were compared with reference values for Whippets. Increased serum creatine kinase activity and hyperkalemia also were sometimes present over the 4‐year period of evaluation. Progressively increasing serum concentrations of N‐terminal prohormone brain natriuretic peptide suggested cardiac disease. Erythrocytes from the whippets were less osmotically fragile but more alkaline fragile than those from control dogs. Erythrocyte phosphofructokinase (PFK) activities and 2,3‐diphosphoglycerate concentrations were decreased. Restriction enzyme‐based DNA test screening and DNA sequencing revealed the same mutation in the muscle‐PFK gene of the Whippets as seen in English Springer Spaniel dogs with PFK deficiency. This is the first report of PFK deficiency in Whippet dogs. In addition to causing hemolysis and exertional myopathy, heart disease may be a prominent clinical component of PFK deficiency in this breed and has not been previously recognized in PFK‐deficient English Springer Spaniels.     

Molecular characterization and identification of markers associated with yield traits in mulberry using ISSR markers

Mulberry (Morus indica L.) is an important tree crop being exploited for feeding the silk‐producing insect Bombyx mori L. In order to identify parents suitable for breeding to raise high‐yielding varieties for the non‐traditional areas of Kerala, India and also to identify markers associated with leaf yield attributing traits, the present study was undertaken with 44 mulberry genotypes. Variability on morpho‐biometric traits and molecular markers, generated with 12 selected ISSR primers, was estimated. Significant differences between genotypes were observed for all the traits. The dendrogram generated with morpho‐biometric characters clustered the genotypes into three distinct groups and one isolate, while the same using Inter simple sequence repeat (ISSR) markers clustered the genotypes into five groups and six isolates. The greater resolving power of the ISSR markers was evident form the dendrograms. Using step‐wise multiple regression analysis, a number of markers associated with number of branches, total shoot length, leaf weight, internodal distance, leaf chlorophyll, protein, leaf moisture percentage were identified. These markers could be of much use in Marker assisted selection (MAS) breeding programmes in mulberry, especially when no genetic information in terms of linkage maps and Quantitative Trait Locis (QTLs) is available a plant with high heterozygosity and a long juvenile period.     

Nitrogen release from plant‐derived and industrially processed organic fertilizers used in organic horticulture

As a consequence of the BSE crisis, alternatives for fertilizers derived from animal residues are being sought for use in organic horticulture. Grain legumes (milled seeds of pea, yellow lupine, and faba bean) and organic fertilizers of industrially processed plant and microbial residues (Maltaflor®‐spezial, Phytoperls®, Agrobiosol®, Rizi‐Korn) were investigated as to their suitability as a replacement fertilizer. With four soils, incubation studies were conducted to determine net N mineralization of the organic fertilizers, and pot experiments were used to measure the apparent N utilization by perennial ryegrass. The objectives of this study were (1) to determine simple fertilizer characteristics that describe their N release and (2) to compare the suitability of both experimental setups to predict fertilizer N release. At the end of all experiments, net N mineralization and apparent N utilization from Rizi‐Korn was highest compared to all the other organic fertilizers, while pea performed relatively poor. This differentiation between the fertilizers developed during the first 2 weeks. Nitrogen release from the organic fertilizers as described by net N mineralization or apparent N utilization was significantly related to the N content of the fertilizers. Different soils modified this relationship. Two industrially processed fertilizers (Phytoperls®, Agrobiosol®) could not be included into a generalized relationship because N release from these fertilizers was low compared to their N content. It is discussed that the quality of fertilizer C and N affected the N release from the fertilizers. Both experimental setups, incubation and pot experiments, were suitable to describe the release of plant‐available N from the organic fertilizers. However, N release of fertilizers with a low net N mineralization in the incubation experiments was underestimated compared to plant N uptake of ryegrass in the pot experiments. It is concluded that the N content of organic fertilizers indicates, but not predicts their N release.