Contribution of nitrogen fixed by Azospirillum to the n nutrition of spring wheat in Israel

Acetylene reduction activity (ARA) was measured in cores containing roots of various Israeli wild and cultivated wheat lines colonized by Azospirillum. The inoculated plants were grown under greenhouse or field conditions. Although, no measurable ARA was detected during earlier stages of wheat development, 50–600 nmol C₂H₄ g^?1 dry root h^?1 was measured during heading and flowering stages. By using N yield balance and ¹⁵N dilution techniques, it was found that Triticum aestivum cv. Miriam inoculated with Azospirillum accumulated 20% more N (¹⁴N and ¹⁵N) at the booting stage than did the uninoculated control. This difference in N content became less apparent in grains. No significant ¹⁵N dilution could be found and the contribution of atmospheric N₂ to the N content of grains of inoculated plants was negligible. It was concluded that the potential contribution of biological N₂ fixation to spring wheat cultivation in Israel is very low.     

Enhanced Removal of Micropollutants from Groundwater,Using pH Modification Coupled with Photolysis

Direct ultraviolet (UV) photolysis coupled with modification of solution pH was explored as a method for the removal of organic micropollutants from groundwater. Photodegradation rates of most of the investigated compounds were pH dependent, however, its correlation with photodegradation rate varied among compounds. The potential of the pH modification during photolysis was determined for removal of a mixture of two pharmaceuticals sulfamethoxazole (SMX) and triclosan (TCS) in groundwater. The treatment included initial photolysis of the mixture at the optimal pH for TCS (i.e., 7.5–7.9), followed by pH modification to the optimal pH for SMX (i.e., 5), prior to a second irradiation period. The described procedure dramatically increased the removal efficiency (up to threefold) of the treated mixture compared to UV treatment at constant pH.     

Fly ash concentrations in philadelphia aerosol determined by electron microscopy

In a study to differentiate between coal-fly ash and minerals in the atmosphere, samples were collected on Nuclepore filters in dichotomous samplers and analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry. The samples included ambient aerosol from two sites, resuspended soil, and emissions from coal- and oil-fired power plants in the Philadelphia area. Fly ash and minerals were identified by observing high abundances of Al, Si, K, Ca, Ti, and Fe in individual particles, and their mass concentrations were estimated from measured dimensions and an assumed density. Fly ash was distinguished from minerals by morphology. Sulfate was the major component of the fine fraction (<2.5 μm aerodynamic dia.). Crustal matter concentrations in the fine fraction estimated by SEM ranged from 40 to 300 ng m^?3, and fly ash accounted for 7 to 62% of the crustal matter. In the coarse fraction (2.5 to 10 μm), minerals were the predominant component and ranged in concentration from 500 to 6000 ng m^?3. Fly ash accounted for 0 to 16% of the crustal matter; the typical amount was 6%. Other less abundant coarse particles included botanical matter and industrial source emissions. Coarse fraction crustal matter estimated from x-ray fluorescence elemental data agreed well with that based on electron microscopy.     

Comparative study of biochemical parameters in response to stress in Oreochromis aureus, O. mossambicus and two strains of O. niloticus

This study was aimed at detecting differences among tilapia species in immunological and biochemical parameters that are indicators for fish health. In addition, six blood parameters that are indicators of stress were measured, glucose concentration, ceruloplasmin activity, lysozyme activity, respiratory burst activity, haematocrit and leucocrit, and their levels were compared among groups. A calibration experiment was conducted with commercial stock of tilapia to optimize a protocol for measuring stress response in tilapia. An air exposure stress was induced to six groups of fish and blood samples were taken at six different times: 15 min, 1, 2.5, 4.5, 6 and 24 h, after inducing stress. The highest responses to stress were observed after 2.5–4.5 h. A second experiment was conducted with four tilapia species: Oreochromis aureus (Steindachner), O. mossambicus (Peters), a red strain and the wild type of O. niloticus L. Levels of serum biochemical components and parameters of the innate immunity response to stress were compared in ten fish from each species. Significant differences were observed. Oreochromis aureus differed from the other three species (notably from O. mossambicus) in most of the measured immune response traits (glucose concentration, lysozyme activity, haematocrit and levels of total protein and IgM after stress) and serum biochemical components (protein, albumin, triglyceride, cholesterol, calcium, magnesium, phosphorus, bilirubin and β‐hydroxybotiric acid). The identified differences suggest that hybrid families from O. aureus and O. mossambicus may be used to construct a segregating population for genetic analysis of the innate immune response to stress. Thus, these two species were bred for segregating F₂ population, suitable for quantitative trait loci studies for the innate immune response to stress.     

Culture of organic tilapia to market size in periphyton‐based ponds with reduced feed inputs

In fish production under organic standards, only organic feeds and manures can be supplied. The cost of organic pelleted feeds is twice that of regular feeds. To support the organic production of hybrid tilapia [Oreochromis niloticus (L.) ×Oreochromis aureus (Steindachner)], a series of experiments in earthen ponds, to improve natural food production for this fish while reducing costs of added feed, are in progress. To improve natural food production for tilapia, plastic substrates equivalent to 50% of the pond surface were introduced into the water column to induce periphyton growth on them. To reduce costs, the feeding rate on pelleted feed was reduced to 60%. Tilapia growth in these periphyton ponds was then compared with ponds without underwater substrates that received the full feed rate. The polyculture consisted of 90% large (320 g stocking weight) hybrid tilapia and small amounts of other fish, at a total stocking density of 13 800 fish ha^?1, during 87 summer days. The results showed improved nitrification and the development of a large autotrophic periphyton biomass that competed with the phytoplankton in the periphyton ponds, and only a 10% and 15% reduction, respectively, in the tilapia daily and specific growth rates, with 40% feed saving. These results point towards periphyton‐based aquaculture as an appropriate technology for the reduction in production costs, allowing economically viable organic tilapia production.