Food selection by freshwater snails in the Gezira irrigation canals,Sudan

Stomach content analysis was carried out on samples of the freshwater snail species Biomphalaria pfeifferi, Bulinus truncatus, Bulinus forskalii (Pulmonata, Planorbidae), Lymnaea natalensis (Pulmonata, Lymnaeidae), Melanoides tuberculata, Cleopatra bulimoides (Prosobranchia, Thiaridae) and Lanistes carinatus (Prosobranchia, Ampullariidae) from different irrigation canals in Sudan. In order to evaluate overlap in diet selection among these species, sites with two or more of the above-mentioned species present were selected. For some species food choice was examined in relation to size groupings. In addition, samples of Marisa cornuarietis (Prosobranchia, Ampullariidae) from small ponds in Sudan, samples of Biomphalaria pfeifferi and Helisoma duryi (Pulmonata, Planorbidae) from drainage canals in an irrigation scheme in northern Tanzania, and samples of H. duryi from fish ponds in the coastal area of Kenya were also analysed. The results indicate a great similarity in the food choice of these species, especially among the pulmonate species. All species feed on fine detritus, epiphytic algae and decaying macrophytes. No fresh fragments of aquatic macrophytes were found and animal remains were found only on a few occasions. However, the stomach contents of the ampullarid species were characterized by large fragments of dead macrophyte tissue, while the composition of the finer particles showed a great resemblance to that of the pulmonate species. The diet of the thiarid species is essentially the same as that of the pulmonate species, although in one site Cleopatra bulimoides showed a greater preference for green algae. Apart from the avoidance of blue-green algae, there was little evidence of selection of certain algal components of the Aufwuchs for the pulmonate species. Detritus constitutes the major component of the stomach content of all these snail species.     

Physiological cotton wilt in the Sudan Gezira

Cotton wilt of physiological origin appears to have been present in the Gezira area of the Anglo-Egyptian Sudan since 1924 if not previously. The present investigations showed that between mid-October and mid-December three factors occur which cause water stress in the crop. At some time during this period there is marked reduction in the size of the absorbing system of the plant, correlated with maximum boll development. Greatly increased day temperatures and higher evaporation prevail, while during the whole period available water in the soil declines. The hypothesis is put forward that when all three factors occur at the same time at their maximum intensity, permanent wilting and death of the plants result; at lesser intensities, wilting is followed by recovery, but with reduction of yield. Experiments are described, the results of which appear to confirm this view. In the author's opinion a return to the earlier sowing date formerly favoured locally would lead to considerably increased losses.     

Ammonium fixation in the Sudan Gezira soils

Summary Laboratory studies showed that the Gezira soils contain appreciable amounts of fixed ammonium. Values for the surface soils varied from 0.25–0.30 me/100g. The soils have the capacity to fix a large quantity of applied ammonium.In the two soil profiles studied the amounts of fixed ammonium and the ammonium-fixing capacity increased with depth reaching a maximum in the grey layer at a depth of about 70 to 140 cm below which it decreased again. The fixed ammonium values varied from 0.28 to 0.40 me/100g and comprised from 5.0 to 5.9 per cent of the total ammonium-fixing capacity (oven-dry condition). When expressed as percentage of Kjeldahl nitrogen the fixed ammonium increased with depth, varying from 12.5 to 20.2 per cent. As expected the amount of fixed ammonium was found to depend on the type and amount of the clay minerals present.The current cropping and fertilization practices were found to have very little effect on the fixed ammonium content of the soil, but it is expected from the high-fixing capacity of these soils that the amount of fixed ammonium will increase with the increase in frequency and dose of NH₄-N fertilizers application     

Nitrogenous fertilizer transformations in the sudan Gezira soil

Summary and Conclusions Direct measurements were made of losses of ammonia during the transformation of urea and ammonium sulphate, surface-applied to alkaline Gezira soil in containers incubated in the field, under different rates of nitrogen application and moisture conditions.The highest rate of ammonia loss occurred during the first week after application with both fertilizers, thereafter decreasing to lower values. The cumulative ammonia loss was higher with higher application of nitrogen. Ammonium sulphate gave consistently higher ammonia losses than urea and losses from open soil system were generally less than from soil in polythene bags.With lowest irrigation level used, ammonia loss attained a sizeable value throughout the incubation period with both fertilizers. With the higher moisture levels, the magnitude of ammonia loss decreased appreciably, much more so with urea than with ammonium sulphate. Induced drying and rewetting prolonged the duration of loss and increased the magnitude of cumulative loss. An appreciable loss of ammonia may take place from fertillzed Gezira Soil under warm conditions, low moisture levels and high fertilizer concentration; this may be the case with patchy fertilizer distribution and frequent light showers during early summer. It is advisable to apply the urea or ammonium sulphate when conditions are most favourable for nitrification.     

Nitrogenous fertilizer transformations in the Sudan Gezira soil

Summary and conclusions 1. Studies of the transformation of urea and ammonium sulphate in the Sudan Gezeira soil, when incubated under field conditions in polythene bags, were carried out with two rates of nitrogen, different moisture levels and frequency of wetting and drying during the winter and summer months.2. The pattern of the transformation was nearly the same for the two levels of nitrogen added but there was a difference in magnitude. Urea hydrolysis was arrested during the first week in the open-bag system in the summer months. A low recovery of ammonia with ammonium sulphate and urea was associated with early ammonia volatilization losses.3. There was a marked accumulation of nitrite in the first two weeks especially in moist closed bags, thereafter it decreased to low values.4. Nitrate accumulated gradually under winter conditions, more so with closed bags than open ones. By contrast, little nitrate nitrogen was formed during the hot summer months, this being associated with high ammonia accumulation throughout the incubation period.     

Survey of soil fungi from the Sudan Gezira

One hundred and twenty sites, from six localities from the Sudan Gezira were examined for soil mycoflora. The lower fungi were mostly represented by mucoraceous genera, such as Rhizopus, Mucor and Cunninghamella. Oomycetes were rare. Ascomycetes, other than the perfect states of Aspergillus, were not common. Only Chaetomium globosum was isolated from the six localities. Monascus, Thermoascus, Neocosmospora and Pyronema were recorded for the first time from Sudanese soils. The majority of the isolates were Hyphomycetes. The bulk of the fungal population were species of Aspergillus, of which A. niger was the most common, followed by A. terreus, A. flavus, A. nidulans and A. fumigatus. Other Aspergilli were sporadic. A. niveus and A. sejunctus were not previously reported from Sudanese soil.     

Enzymatic activity of a soil profile in the Sudan Gezira

Summary In preliminary work in the enzymatic activity of a semi-arid Gezira soil microbes were counted and urease, dehydrogenase, and Catelase activities were measured in five soil horizons from 0 to 72 inches depth. Urease and dehydrogenase activities of unamended soil from all horizons appeared to be better indicators of biological status than catalase activity. Biological activity was marked in the top soil (0–2 inches) — the zone of grass root activity — but decreased gradually to reach a low level in deeper horizons.     

Spoilage of stored cotton fibre from Sudan Gezira

Washings from long staple cotton (Gossypium barbadense L.) new variety Barakat, yielded Aspergillus flavus, A. nidulans, A niger. A. terreus, A. versicolor and Cladosporium herbarum. The number of propagules increased with R. H. following 6 month-storage. A. terreus was less favoured.Higher R. H. impaired fibre length and strength of both raw non-sterilized and inoculated sterile lint whilst the sterilized non-inoculated control was insignificantly affected, even at 100% R.H. Artificial inoculation of lint with Chaetomium globosum and A. nidulans significantly affected the efficiency of yarn spinnability at 80, 90 and 100% R.H. (P=0.05).Hyphae, which wound in a helical pattern around the fibre, intermittently dissolved fibre wall causing fibre fragility.     

Nutrient uptake in a stream affected by hydropower plants: comparison between stream channels and diversion canals

Small hydropower plants divert part of the water from wide and physically complex stream channels with active hyporheic areas to narrow and hydraulically simple concrete canals, and thus, might affect nutrient dynamics. We compared nutrient uptake in diversion canals and in stream channels in the Leitzaran Stream (Basque Country, northern Spain). We predicted that simple morphology in diversion canals will result in lower nutrient uptake in canals than in stream channels. Periphytic chlorophyll and biomass did not differ significantly between reach types. Water was significantly deeper and faster in canals than in stream channels, but the transient storage zone did not differ significantly between reach types. There were no significant differences between uptake length for neither phosphate nor ammonium between reach types. Uptake length in both stream channels and diversion canals decreased with discharge, in a pattern similar to that previously described for pristine rivers across the world. Uptake velocity and uptake rate for phosphate did not differ significantly between reach types, but in the case of ammonium both retention metrics were significantly larger in the diversion canals. Results suggest that although hydropower schemes have minor effects on nutrient retention, these depend on the proportion of flow diverted.     

The course of resin canals in the shoots of conifers

The course of resin canals in stem cortex and the continuity between resin canals in leaves and those in stem cortex were investigated. The present paper is the first of three parts of the investigation. In this paper, fundamental features of resin canals and actual resin canal patterns in the Taxaceae, Cephalotaxaceae and Podocarpaceae are reported. From the observation of serial transections of shoots, composite diagrams and three-dimensional models of resin canal patterns are drawn. Central canals, if present, run vertically in stem cortex and sometimes divide, end blindly or unite each other. The distance between two adjacent central canals fluctuates rhythmically in connection with the vascular supply from the stem to leaves. The resin canal patterns of the families are classified into four types. Those ofTaxus, Nothotaxus and three species ofDacrydium belong to the Taxus type, those ofTorreya andCephalotaxus to the Torreya type, those ofDacrydium elatum, Podocarpus alpinus, P. elatus, P. elongatus andP. neriifolius to the Dacrydium type, those ofP. macrophyllus, P. nagi andP. koordersii to the Podocarpus type.     

The course of resin canals in the shoots of conifers

Resin canal patterns in the Pinaceae differ significantly from those in other conifers. In this paper, Pinus type, Picea type and Larix type are defined.Pinus has the Pinus type pattern, in spite of the possession of a system of peripheral canals in some members. The patterns inAbies, Picea, Cedrus, Keteleeria andPseudotsuga are varied. Both Pinus and Picea types are usually observed, although many other types are also seen in these five genera.Larix andPseudolarix have the Larix type pattern, andTsuga has a modified Torreya type pattern. From the data obtained in the present series of studies (Suzuki, 1979a, b), two main evolutional trends of resin canal patterns are suggested. In the Pinaceae, the patterns probably evolved from the complicated type to the simple type. In the other families, they evolved from the simple type to the complicated type. Moreover, it is to be considered likely that the patterns have evolved independently in each family. Patterns of resin canals are very similar to the primary vascular patterns. The similarity is probably not fundamental, but superficial, because most of the conifer species, of which resin canal patterns are varied, have but a single type of the primary vascular system.     

Morphometric analysis of cartilage canals in the developing mouse epiphysis

Cartilage canal development in the distal femoral epiphysis of 5- to 7-day-old mice can be divided into three stages as previously described [Cole and Wezeman, Am. J. Anat. 174: 119-129, 1985]. Using this model, a morphometric analysis of canal volume density at the three stages of development was performed and provided evidence that canal formation significantly exceeds epiphyseal growth. These data are consistent with initial canal formation by invasion rather than by inclusion.     

Identification of a distinct strain of Cotton leaf curl Gezira virus infecting tomato in Oman

Tomato (Solanum lycopersicum) plants exhibiting yellowing, curling and stunting symptoms were identified in fields of the Tawoos Agricultural Systems, in Al‐Batinah in Oman. Cloning and sequencing of restriction endonuclease digested rolling circle amplified viral DNA identified a cotton begomovirus (family Geminiviridae) associated with the symptomatic tomato plants. Detailed analysis of complete sequences showed the virus to be a previously unknown strain of Cotton leaf curl Gezira virus (CLCuGeV) in association with the betasatellite Tomato leaf curl betasatellite (ToLCB). The new CLCuGeV strain, for which the name “Al Batinah” strain is suggested, has the greatest levels of sequence identity (91.9%) to an isolate of CLCuGeV recently reported from the neighbouring United Arab Emirates. Additionally, CLCuGeV‐Al Batinah was shown to have a recombinant origin with sequences donated by an African cassava mosaic virus‐like parent. This is the first identification of this Malvaceae‐adapted begomovirus in tomato. Although ToLCB is common in Oman, being one of only two betasatellites identified there so far, this is the first identification of this betasatellite with CLCuGeV. The significance of these findings is discussed.     

Perivascular cells in cartilage canals of the developing mouse epiphysis

Morphological variability among perivascular cells adjacent to cartilage matrix during the elongation of canals through both uncalcified and calcified matrix has not been reported. Cartilage canals were located in distal femoral epiphyses of 5- to 7-day-old mice and identified as vascular channels arising from perichondrial surfaces along the condyles and intercondylar fossae. Three stages of canal development were identified based on the length of canals and on characteristics of chondrocytes and matrix surrounding the canals. Superficial canals terminated in uncalcified matrix of resting cartilage; intermediate canals terminated in matrix containing hypertrophic chondrocytes; deep canals terminated in calcified matrix. The ultrastructural morphology of perivascular cells in contact with the matrix varied in the three stages. Cells resembling fibroblasts and vacuolated macrophages were present adjacent to the uncalcified matrix in superficial canals. At the tips of intermediate canals, cells resembling fibroblasts were larger, contained numerous lysosomes and phagolysosomes, and were in intimate contact with the matrix. At the tips of deep canals, chondroclasts with ruffled borders and clear zones contacted the calcified matrix. The results indicate that 1) mouse epiphyses provide a suitable model for studying cartilage-canal perivascular cells, 2) calcification of cartilage matrix occurs along the course of the canal, and 3) the morphology of perivascular cells in contact with the matrix may be determined, in part, by matrix calcification.