Economic factors and opportunities as determinants of water use efficiency in agriculture

A consequence of water scarcity is that it has enhanced research and development aimed at increasing water use efficiency in irrigated agriculture. Although biological, genetic, and technological achievements may induce potential high levels of water use efficiency, actual observed values may be much smaller. This paper distinguishes between potential and actual water use efficiency measures, and discusses factors and opportunities that may affect actual water use efficiency in irrigated agriculture. These include economic forces, environmental effects, and institutional arrangements, each of which may affect water use decisions at field, farm, regional, and national levels. The paper develops a scheme to generally address differences between private and social considerations that determine water use efficiency decisions. Using this scheme, several examples from California and Israel are provided to support the arguments. The paper concludes that the concept of water use efficiency is much broader than its definition: yield per water applied or transpired. Moreover, determination of water use efficiency levels in irrigated agriculture is a complex issue that requires interdisciplinary considerations.     

Differential effects of spot blotch on photosynthesis and grain yield in two barley cultivars

Barley spot blotch (SB), caused by Cochliobolus sativus, is an important barley disease which causes extensive grain yield losses. These losses may not always correlate directly with the amount of diseased leaf area. Two barley cultivars, Quebracho (susceptible to SB) and Carumbé (with intermediate susceptibility to SB), were compared in field experiments in 2003, 2004 and 2006. Plots of each cultivar were either inoculated with C. sativus or protected with fungicide under field conditions to generate contrasting treatments: i) diseased, and ii) free of disease, respectively. SB severity over the growing season, photosynthetic rate on leaves with no visible symptoms and grain yield were assessed for each treatment and year. There was no treatment effect on cv. Carumbé, while cv. Quebracho showed a significant yield reduction, even though SB severity during the grain filling period was <10 %. This yield reduction was associated with a reduced photosynthetic rate at the beginning of the grain filling period in cv. Quebracho. A similar experiment was conducted under greenhouse conditions, adding a treatment without inoculum or fungicide. There were no differences in photosynthetic rate or grain yield per plant among treatments. These results suggest a distinct physiological response to SB infection among cultivars affecting leaf photosynthetic rate, and SB severity may not be the best estimator of yield losses caused by SB.     

Effects of constant light on haematological parameters of cultured rainbow trout (Oncorhynchus mykiss) in the Southern Hemisphere

The effects of artificial photoperiod regimes on reproductive patterns have been studied in several species, as have haematological parameters. However, information on how artificial photoperiods may affect blood components is scarce, especially under field conditions. We have assessed the effects of constant light [long day (LD) photoperiod: 24 h (light):0 h (dark)] on haematological parameters of cultured rainbow trout in Chile (Southern Hemisphere). In the initial stage (March up to June), two groups of fish were maintained under similar conditions and under the ambient (natural) photoperiod (NP). One group was then placed under the LD photoperiod regime for 2 months (June/July), following which it was returned to␣the NP (August–January); the control group remained under the NP throughout the experiment (March–January). All fish were assessed for haematological parameters and growth performance at various times during the experiment. During the initial stage, no differences were found between groups. However, at the end of the LD 24:0 period, the LD fish had increased haematocrit values and erythrocyte numbers and diminished mean corpuscular haemoglobin. After the LD fish had been returned to the NP, they developed secondary sexual characteristics and had a 40–44% decrease in the number of leukocytes.     

Vertical distribution of phosphorus in a sandy soil fertilized with recovered manure phosphates

Purpose  

The aim of the study was to evaluate the environmental fate of recovered manure phosphates for their effective use as crop fertilizers.     

Phylogeny of Coccomyxa (Myxosporea: Myxidiidae) spp. with the description of a new species from Bathygobius cyclopterus (Gobiidae) in the northern Red Sea

Two species of Coccomyxa Léger et Hesse, 1907, one of the least studied myxosporean genera, are reported from shallow coastal waters in the Gulf of Eilat, Red Sea, Israel. A new species, Coccomyxajirilomi sp. n. is described from the spotted frillgoby Bathygobius cyclopterus (Valenciennes) (Gobiidae). It forms polysporous plasmodia that invade the liver and form packed clusters inside the bile ductules. Plasmodia also occur in the bile ducts and gall bladder of the host, attached to the epithelial lining or free floating in the bile. Infected hepatic bile ductules packed with plasmodia were partially occluded, with evidence of cholestasis, periductular fibrosis and pericholangitis. The mature spore is ellipsoid, has smooth valves and contains a single polar capsule with the polar filament arranged in 4-5 oblique coils. Spore dimensions are 9.0-11.3 x 5.0-7.0 microm. A second species, Coccomyxa sp., with smaller 7.6-9.6 x 4.2-5.2 microm and more delicate spores, was found in the gall bladder of the rippled rockskipper, Istiblennius edentulus (Forster et Schneider) (Blenniidae). The small subunit (SSU) rDNA sequence analysis of both Coccomyxa species suggests that they are closely related to members of the genera Myxidium, Zschokkella and Auerbachia, whose members infect the gall bladder of marine fish.     

One-step derivatization and preconcentration microextraction technique for determination of bisphenol A in beverage samples by gas chromatography-mass spectrometry

A simple technique based on ultrasound-assisted emulsification microextraction in situ derivatization (USAEME-ISD) is proposed for the one-step derivatization, extraction, and preconcentration of bisphenol A (BPA) in beverage samples prior to gas chromatography-mass spectrometry (GC-MS) analysis. BPA was in situ derivatized with acetic anhydride and simultaneously extracted and preconcentrated by using USAEME. Variables affecting the extraction efficiency of BPA were evaluated. Under optimal experimental conditions, the detection limit (LOD) was 38 ng L(-1) with a relative standard deviation (RSD) value of 11.6%. The linear working range was 100-1250 ng L(-1), and the coefficient of estimation (r(2)) of the calibration curve was ≥0.9971. The robustness of the proposed methodology was probed by developing a recovery study at two concentrations (125 and 500 ng L(-1)) over different beverage samples. This study led to a satisfactory result achieving recoveries of ≥82%, which showed acceptable robustness for determination of nanograms per liter of BPA in samples of food safety interest.     

Complexes of Cu–Polysaccharide of a Marine Red Microalga Produce Spikes with Antimicrobial Activity

Metal–polysaccharides have recently raised significant interest due to their multifunctional bioactivities. The antimicrobial activity of a complex of Cu₂O with the sulfated polysaccharide (PS) of the marine red microalga Porphyridium sp. was previously attributed to spikes formed on the complex surface (roughness). This hypothesis was further examined here using other Cu–PS complexes (i.e., monovalent-Cu₂O, CuCl and divalent-CuO, CuCl₂). The nanostructure parameters of the monovalent complexes, namely, longer spikes (1000 nm) and greater density (2000–5000 spikes/µm²) were found to be related to the superior inhibition of microbial growth and viability and biofilm formation. When Escherichia coli TV1061, used as a bioluminescent test organism, was exposed to the monovalent Cu–PS complexes, enhanced bioluminescence accumulation was observed, probably due to membrane perforation by the spikes on the surface of the complexes and consequent cytoplasmic leakage. In addition, differences were found in the surface chemistry of the monovalent and divalent Cu–PS complexes, with the monovalent Cu–PS complexes exhibiting greater stability (ζ-potential, FTIR spectra, and leaching out), which could be related to spike formation. This study thus supports our hypothesis that the spikes protruding from the monovalent Cu–PS surfaces, as characterized by their aspect ratio, are responsible for the antimicrobial and antibiofilm activities of the complexes.     

Organization of intracellular reactions with rationally designed RNA assemblies

The rules of nucleic acid base-pairing have been used to construct nanoscale architectures and organize biomolecules, but little has been done to apply this technology in vivo. We designed and assembled multidimensional RNA structures and used them as scaffolds for the spatial organization of bacterial metabolism. Engineered RNA modules were assembled into discrete, one-dimensional, and two-dimensional scaffolds with distinct protein-docking sites and used to control the spatial organization of a hydrogen-producing pathway. We increased hydrogen output as a function of scaffold architecture. Rationally designed RNA assemblies can thus be used to construct functional architectures in vivo.