Altitude,temperature, and N Management effects on yield and yield components of contrasting lowland rice cultivars

Nitrogen (N) is one of the main nutrients that drive rice grain yield and is intensely managed especially in lowlands under irrigated conditions. A set of experiments was conducted in mid- and high-altitude sites in Rwanda to investigate the response of five genotypes under different sowing dates and different N management. Genotype grain yields were higher and more stable at mid-altitude across sowing dates. N rates strongly affected grain yield at mid-altitude (p < .0001), but not at high altitude. Postponing basal N had positive effects on yield and yield components in both sites, with more pronounced effects at high altitude. Increasing N rate beyond 120 kg/ha led to a decrease in percentage of panicles per tiller and spikelet fertility and a decrease in grain yield due to excessive tillers at both high altitude and mid-altitude. Thus, basal N application should be recommended at high altitude and the increase in N rate up to 120 kg/ha at mid-altitude. A strict observation of recommended planting date should be followed at high altitude, and the use of cold-tolerant genotypes is encouraged.     

不同基质中栽培的樱桃番茄在夏季热应激下的反应比较

该文旨在比较研究不同栽培基质(土壤、泥炭、泥炭／珍珠岩(1／2)、珍珠岩和营养液循环系统)中生长的樱桃番茄在夏季受热应激时的反应。试验于2002年7、8、9月进行，番茄分别移植到3个温室中，温度设置为：25/20℃，35/25℃，>35/>25℃，分别在番茄不同生长阶段进行。测试分析了温室内环境因子的变化和气体交互作用：温室内温度与湿度(R²：0.894～0.972)、温度与CO₂浓度(R²：0.668～0.786)之间呈线性关系。测定了番茄的生长率，表明茎伸展与栽培基质密切相关。用叶水势来反映受热应激下番茄的水分状况，表明方差分析显示无论是黎明前还是正午，栽培基质和热应激对叶水势的变化有重要的作用。实验结果可正确确定热胁迫影响的生育时期，并为选择夏季番茄生产的适宜栽培基质提供依据。     

Multiresidue pesticide analysis of agricultural commodities using acetonitrile salt-out extraction, dispersive solid-phase sample clean-up, and high-performance liquid chromatography-tandem mass spectrometry

A multiresidue method analyzing 209 pesticides in 24 agricultural commodities has been developed and validated using the original Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) procedure and high performance liquid chromatography-positive electrospray ionization-tandem mass spectrometry (LC-MS/MS) analysis. Using solvent-only calibration standards (SOCSs) and matrix-matched calibration standards (MMCSs), it was demonstrated that a minimal concentration of 5-10 μg/kg (part per billion, ppb) of analytes in matrix is required for the consistent identification of targeted pesticides with two MRM transitions. Method performance was validated by the precision and accuracy results obtained from fortification studies at 10, 25, 100, and 500 ppb and MMCSs. The method was demonstrated to achieve an average recovery of 100 ± 20% (n = 4) for >75% of evaluated pesticides at the low fortification level (10 ppb) and improved to >84% at the higher fortification concentrations in all 24 matrices. Matrix effects in LC-MS/MS analysis were studied by evaluating the slope ratios of calibration curves (1.0-100 ng/mL) obtained from the SOCSs and MMCSs. Principal component analysis (PCA) of LC-MS/MS and method validation data confirmed that each matrix exerts its specific effect during the sample preparation and LC-MS/MS analysis. The matrix effect is primarily dependent on the matrix type, pesticide type and concentration. Some caution is warranted when using matrix matched calibration curves for the quantitation of pesticides to alleviate concerns on matrix effects. The QuEChERS method with LC-MS/MS was used to identify and quantitate pesticides residues, with concentrations ranging from 2.5 to >1000 ppb in a variety of agricultural samples, demonstrating fitness for screening and surveillance applications.     

POSITRON EMISSION TOMOGRAPHY OF THE EQUINE DISTAL LIMB: EXPLORATORY STUDY

Positron emission tomography (PET) is a highly sensitive, noninvasive imaging technique for quantifying biological functions of tissues. However, at the time of this study, PET imaging applications had not been reported in the horse. The aim of this exploratory study was to determine whether a portable high‐resolution PET scanner could be used to image the equine distal limb. Images of the front feet and fetlocks of three research horses, with known lesions localized to the distal front limbs, were acquired under general anesthesia after administration of ¹⁸F‐fluorodeoxyglucose (¹⁸F‐FDG), with doses ranging from 1.5 to 2.9 MBq/kg. The radiation exposure measured during imaging was slightly higher than ^99mTechnetium scintigraphy. However, the use of general anesthesia allowed the proximity and the contact time with the patient to be minimized for the staff involved. ¹⁸F‐FDG uptake was evident throughout the soft tissues, with the highest uptake in the coronary band and the lowest uptake in the tendons. Anatomic structures could be discriminated due to the high contrast between soft tissue and bone. Detected lesions included lysis of the flexor cortex of the navicular bone, lesions of flexor tendons and suspensory ligament, and abnormal uptake through the lamina of a laminitic subject. Findings indicated that tomographic molecular imaging is feasible in the equine distal limb and could be useful as a future diagnostic technique for clinical and research studies, especially those involving tendinopathy/desmopathy and laminitis.     

Phenolic constituents and antioxidant capacity of four underutilized fruits from the Amazon region

The Amazon region comprises a plethora of fruit-bearing species of which a large number are still agriculturally unimportant. Because fruit consumption has been attributed to an enhanced physical well-being, interest in the knowledge of the chemical composition of underexplored exotic fruits has increased during recent years. This paper provides a comprehensive identification of the polyphenolic constituents of four underutilized fruits from the Amazon region by HPLC/DAD-ESI-MS(n). Arac?a? ( Psidium guineense ), jambola?o ( Syzygium cumini ), muruci ( Byrsonima crassifolia ), and cutite ( Pouteria macrophylla ) turned out to be primarily good sources of hydrolyzable tannins and/or flavonols. Additionally, different flavanonols and proanthocyanidins were identified in some fruits. The antioxidant capacity was determined by using the total oxidant scavenging capacity (TOSC) assay. Cutite showed the highest antioxidant capacity followed by jambola?o, arac?a?, and muruci.     

Cloning and characterization of an 11S legumin, Car i 4, a major allergen in pecan

Among tree nut allergens, pecan allergens remain to be identified and characterized. The objective was to demonstrate the IgE-binding ability of pecan 11S legumin and characterize its sequential IgE-binding epitopes. The 11S legumin gene was amplified from a pecan cDNA library and expressed as a fusion protein in Escherichia coli. The native 11S legumin in pecan extract was identified by mass spectrometry/mass spectrometry (MS/MS). Sequential epitopes were determined by probing the overlapping peptides with three serum pools prepared from different patients' sera. A three-dimensional model was generated using almond legumin as a template and compared with known sequential epitopes on other allergenic tree nut homologues. Of 28 patients tested by dot blot, 16 (57%) bound to 11S legumin, designated Car i 4. MS/MS sequencing of native 11S legumin identified 33 kDa acidic and 20-22 kDa basic subunits. Both pecan and walnut seed protein extracts inhibited IgE binding to recombinant Car i 4, suggesting cross-reactivity with Jug r 4. Sequential epitope mapping results of Car i 4 revealed weak, moderate, and strong reactivity of serum pools against 10, 5, and 4 peptides, respectively. Seven peptides were recognized by all three serum pools, of which two were strongly reactive. The strongly reactive peptides were located in three discrete regions of the Car i 4 acidic subunit sequence (residues 118-132, 208-219, and 238-249). Homology modeling of Car i 4 revealed significant overlapping regions shared in common with other tree nut legumins.     

Comment on "Ongoing adaptive evolution of ASPM, a brain size determinant in Homo sapiens"

Mekel-Bobrov et al. (Reports, 9 September 2005, p. 1720) suggested that ASPM, a gene associated with microcephaly, underwent natural selection within the last 500 to 14,100 years. Their analyses based on comparison with computer simulations indicated that ASPM had an unusual pattern of variation. However, when we compare ASPM empirically to a large number of other loci, its variation is not unusual and does not support selection.     

Optimum Level of Nitrogen and Phosphorus to Achieve Better Papaya (Carica papaya var. Solo) Seedlings Growth and Mycorrhizal Colonization

An experiment under greenhouse conditions was carried out to evaluate the best level of nitrogen (N) and phosphorus (P), which promote the growth of papaya (Carica papaya L. var. Solo) seedlings without affecting the arbuscular mycorrhizal fungi (AMF) activity. Seedlings of papaya were transplanted to pots inoculated or not with Gigaspora margarita spores at four levels of N (0, 50, 100, and 200 ppm) and P (0, 25, 50, and 100 ppm). P was amended at the same time of pot filling up with substrate but N was applied weekly. The experiment was harvested after 100 days and plant dry weight together with AMF colonization was measured. The major response on the plant dry weight and height was from the fertilizers (N and P) where it proportionally increased. For the dry weight, at low amounts of nutrients the effects of AMF were greater, but as much as the fertilizer level in soil increased this response decreased. The colonization decreased as the nutrient levels increased, especially the P. The best combination of N and P for plant growth and AMF colonization could be at 50 and 25 ppm, equivalent to 5 and 2.5 kg/10a, respectively.