<Emphasis Type="Italic"> Gluconacetobacter diazotrophicus</Emphasis>: a natural endophytic diazotroph of Nile Delta sugarcane capable of establishing an endophytic association with wheat

Gluconacetobacter- like diazotrophs were encountered as dense populations inside the root and stem tissues of sugarcane cultivated in ancient agricultural fields of the Nile Delta. Counts of >10⁵ cells g^-1 were recorded in root and stem samples. The leaves contained a smaller population (<10³ g^-1). The typical dark-orange colonies which developed on LGIP agar plates were purified. Identification was performed with the API microtube systems: API 20E for Enterobacteriaceae and API 20NE for non-Enterobacteriaceae. API profiles of the local isolates were closely related to those of the type culture Gluconacetobacter diazotrophicus (ATTC 49037). The isolates successfully reduced C₂H₂ and produced appreciable amounts of ethylene in the presence of cane juice. This suggested that the local isolates are closely related to the type strain G. diazotrophicus. Wheat seedlings were inoculated with a number of isolates under gnotobiotic conditions. Both optical and scanning electron microscopy showed that endophytic Gluconacetobacter spp. were present in all the samples tested. They were observed in apparently intact and enlarged epidermal root cells, and also in stem tissues, indicating that the bacterium was able to migrate upward into the shoot tissues. Although Gluconacetobacter inoculation did not stimulate the growth of the cereal plant, the results obtained are particularly interesting because this bacterial species was capable of colonizing the internal tissues of wheat, not considered a natural host until now.     

Purification of Raw Surface Water Using Electro-Coagulation Method

The purification of raw surface water from its organic, inorganic and microbial content using the electro-coagulation method was investigated. Batch coagulation experiments were conducted using the jar-test method. A pair of aluminum electrodes (suspended in the jar) was charged with low voltage current for releasing aluminum ions in the raw water to precipitate the suspended matter. The optimum current density was 0.6325 mA cm^–2. The coagulation efficiency was evaluated by determining the turbidity of treated water. The efficiency reduction in raw water turbidity was 90%, leading to a change in water Zeta potential from –85 mV (before treatment) to –40 mV (after treatment), i.e. the particles tended to be destabilized and the coagulation process became predominant. Water contents of nitrates, phosphates and sulfates were considerably reduced by 77.5, 83.3 and 20.0%, respectively. Also, this method is effective in reducing both the total viable bacterial count (TVBC) and total coliforms (TC) by a ratio of 1/10⁴ and 1/10³, respectively.     

Exploiting the potential of indigenous fruit trees: <Emphasis Type="Italic">Grewia tenax</Emphasis> (Forssk.) Fiori in Sudan

The small leaved white cross berry (Grewia tenax [Forssk.] Fiori) is a fruit-producing deciduous shrub or small tree of widespread occurrence in semi-arid and sub-humid tropical climates. Despite its well-recognized potential and high prices on local markets, there are no commercial plantations in Sudan. Wild plants have continuously been used to meet the growing commercial demand for their fruits. Recently, there has been an increased interest in finding alternative, potentially high-value cash crops to improve the income of small farmers who are currently depending upon growing and selling millet (Pennisetum glaucum [L.] R. Br.), sorghum (Sorghum bicolor [L.] Moench), sesame (Sesamum indicum L.), and groundnut (Arachis hypogaea L.). G. tenax has often been cited as a prime candidate for domestication as a useful horticultural plant. One major factor hampering this development is the limited and scattered knowledge available on this species. The purpose of this paper is to highlight the importance of G. tenax by providing information on its botanical and horticultural characteristics in the effort to promote its domestication and commercialization for regional and global markets.     

Influence of origin and extraction method on argan oil physico-chemical characteristics and composition

Twenty one samples of argan oil of different geographical origin (Tidzi, Tamanar, Benaiznassen, Ait mzal, Ait Baha, Ighrem, Aoulouz) and/or prepared following a different process (traditional, mechanical, or industrial) were collected and their physico-chemical properties analyzed. Sample acidity was found between 0.14 and 1.40%, unsaponifiable matter between 0.34 and 0.79%, saponification value between 180.0 and 199.6, highest peroxide index was 5.72 meq/kg, refractive index (20 degrees C) between 1.4644 and 1.4705, and UV absorption at 270 nm between 0.228 and 0.605. This study, carried out on randomly selected samples, clearly demonstrates that press extraction does not alter either the chemical composition of argan oil or its physico-chemical characteristics. It also demonstrates that press extraction respects the critical factors reported for traditionally prepared oils and necessary to obtain a beneficial effect on human health (a specific fatty acid balance and high tocopherol and sterol levels). In addition, this study should be useful for the establishment of a national quality standard.     

Variation of Agro-morphological Characters in Moroccan Barley Landraces Under Near Optimal and Drought Conditions

In many areas of North Africa, barley is often the only possible rainfed crop. In these regions water deficit is the primary constraint affecting crop production. Twenty barley landraces collected from different localities in south Morocco and four modern varieties were characterized in two field experiments, one under well-irrigated and one under limited-irrigated conditions. Nine agro-morphological characters were evaluated: Plant height, tiller number per plant, number of grains per spike, number of spikes per plant, spike weight, spike length, plant weight (PW), number of internodes of rachis (NIR), and length of the last internode of rachis. The correlation coefficients among characters were nearly the same in the well- and limited-irrigated experiment. Under limited-irrigated conditions, plant growth was significantly decreased as measured by all characters except NIR, which was unaffected. The percentage of reduction, ranging from 80.08% to 5.82%, was recorded on PW and NIR, respectively. The injury index ranging from 4.02 to 0.06 was recorded on PW and NIR, respectively. Using discriminant analysis the genotypes were arranged in three, clearly separated groups that varied in their tolerance to drought stress.     

Advantages of using non-isothermal bioreactors in agricultural waste water treatment by means of immobilized urease. Study on the influence of spacer length and immobilization method

The behavior of three different catalytic membranes, obtained by immobilizing urease on nylon sheets chemically grafted with methyl methacrylate, was studied in a bioreactor operating under isothermal and non-isothermal conditions. Membrane activation was carried out by condensation or acyl azide reaction, and spacers of different lengths, such as hexamethylendiamine or hydrazine, were used. Under isothermal conditions, the activities of the catalytic membranes and soluble urease were characterized as a function of pH, temperature, and urea concentration. Both enzyme forms showed the same optimum pH, whereas the optimum temperature was lower for the immobilized enzymes. The spacer length appeared to determine broader pH- and temperature-activity profiles for the urease derivatives. The apparent K(m) values of the insoluble urease were dependent on membrane type and were higher than those of the soluble counterpart, thus indicating an affinity loss for urea. Under non-isothermal conditions, all membranes exhibited an increase of percentage activity proportional to the applied temperature difference and decreasing with the increase of urea concentrations. A decrease of the apparent K(m) was also observed. These results suggest that substrate diffusion limitations due to the immobilization process can be overcome in the presence of temperature gradients. In addition, the remarkable reduction of the production times supports the use of non-isothermal bioreactors for the treatment of urea-polluted waste waters.     

Heavy Metals Pollution of the Atlantic Marine Environment by the Moroccan Phosphate Industry, as Observed through their Bioaccumulation in Ulva Lactuca

The Moroccan phosphate industry releases large amounts of heavy metals in the Atlantic Ocean in the surroundings of two places: Safi and Jorf Lasfar. The major waste, called phosphogypsum and composed of calcium sulphate and other additional salts, is introduced into sea water in particulate form. After dissolution of the particles, heavy metal concentrations can be influenced near the release point. Two multi-element analytical techniques were used to measure 47 element concentrations in various materials involved in the study of the phosphate pollution: Inductively Coupled Plasma Mass Spectrometry (ICPMS) and instrumental neutron activation analysis (INAA). At first, phosphate and phosphogypsum were characterized in order to recognize the overall features of the heavy metal pollution source. From the yearly amount of phosphogypsum produced by the Moroccan industry and the element concentrations in phosphogypsum, it has been possible to estimate a yearly flux of heavy metals introduced in the Atlantic Ocean. Algae were used as bio-accumulator materials of heavy metals in the marine environment, in the region of Jorf Lasfar, in order to significantly reveal the signal of the heavy metal pollution. Ulva lactuca Linnaeus was selected to assess heavy metal pollution around the waste release point. Accumulation factors were determined for 47 elements in U. lactuca, by comparing mean concentrations obtained in algae collected in non-polluted sites (background sites) and an average sea water concentration given in the literature. The ratio between the concentration in U. lactuca, collected in a polluted site to the background concentration in U. lactuca, was determined, giving an estimate of the pollution factor for the same elements by the phosphate industry. The decrease of the pollution due to the dilution in the sea water was observed as far as 6 km southward of the release point. A specific variation was observed for lead and its isotopic composition, denoting that the phosphate industry is not the only pollution source in this region. Natural processes were likely involved to induce the lead concentrations variations along the littoral.     

Estimation of air quality degradation due to Saharan dust at Nouakchott, Mauritania, from horizontal visibility data

It is now irrefutable that air pollution caused by large amounts of Total Suspended Particulates (TSP) and respiratory particulates or Particulate Matter less than 10 μm in aerodynamic diameter (PM₁₀) has numerous undesired consequences on human health. Air quality degradation far from the African continent, in the US and in Europe, caused by high concentrations of African dust, is seen as a major threat even though most of these countries are very distant from the Sahara. Surprisingly, no estimates of TSP or PM₁₀ levels near the Saharan dust source are available. Based on horizontal visibility observations which are reduced by the presence of dust in the atmosphere, TSP and PM₁₀ levels are estimated throughout the year 2000 at Nouakchott-Airport, Mauritania, using relations found in the literature. It appears that concentrations of particles are significant both in terms magnitude and frequency, as the 24-hour PM₁₀ thresholds established by the US EPA National Ambient Air Quality Standards and the EU Limits Values for Air Quality were exceeded 86 and 137 times, respectively. The average annual concentration is far above air quality standards and estimated at 159 μg m^?3 for TSP and 108 μg m^?3 for PM₁₀. These very high particulate levels are likely to represent an important public health hazard and should be considered as a major environmental risk.     

Isozymic polymorphism and phylogeny of 10 Lathyrus species

Isozyme variation and phylogenetic relationships between ten annual andperennial Lathyrus species: L.aphaca, L.articulatus, L.cicera, L.hirsutus, L.latifolius, L.nissolia, L.odoratus, L.ochrus, L.sativus and L.sylvestris were studied. Four enzyme systems,leucine-amino-peptidase (LAP), 6-phosphogluconatedeshydrogenase (6-PGD), glutamateoxalo-acetate transaminase (GOT) and phosphoglucoisomerase(PGI) were analyzed, using gel electrophoresis. Fivepolymorphic loci were detected and eleven alleles were identified at these loci.Zymogram data revealed that almost all-present species studied exhibited isozymepolymorphism. L. latifolius andL. sylvestris maintain high levels ofisozyme diversity, which is probably associated with the perenniality of thesetwo species and their predominantly outcrossing reproduction system. Incontrast, the low level of genetic diversity observed in other species isattributed to their breeding systems. These species are annuals and have higherproportions of selfing. The distribution of genetic variation within and amongspecies showed large genetic differences between the analysed species.PGD-1 andPGD-2 loci contributed the most to thedistinction between species. GOT-2,LAP-1 and PGI-1loci contributed to the distinction within species. The low level of gene flowrevealed could be partly related to the high level of autogamy in the majorityof species. The regroupement of species revealed by Nei's genetic similarityagrees only in parte with Kupicha's classification based on morphologicalcharacters. Thus, these isozymic markers are important in germplasm collectionand conservation.