The release of silicon from amorphous silica and rice straw in Sri Lankan soils

Silicon release from rice straw and amorphous silica when shaken in solution with five Sri Lankan soils was studied indirectly using sorption isotherms and changes in concentration and directly using straw in dialysis bags examined using electron microscopy. The aim was to further our understanding of the processes and factors affecting the release of straw-Si in soils and its availability to rice. The soils (alfisols and ultisols) shaken with 0.1 M NaCl (5 g per 125 mL for 250 days) produced concentrations of 1–4 mg L⁻¹ of monosilicic acid-Si. Amorphous silica added to these suspensions (36.5 mg, containing 17 mg Si) raised the concentrations to 20–40 mg L⁻¹, and added rice straw (0.5 g, containing 17 mg Si) gave 10–25 mg L⁻¹. Sorption isotherms (7 days equilibrations) were used to calculate from the concentrations the amounts of Si released (24–38% and 8–21%, respectively). Both materials gave about 40 mg L⁻¹ of monosilicic acid-Si plus 30 mg L⁻¹ of disilicic acid-Si when shaken in solution alone (5 g per 125 mL). Straw in dialysis bags (0.5 g per 25 mL in 0.1 M NaCl) was shaken in soil suspension (5 g per 100 mL) for 60 days. Similar concentrations and releases were measured to those obtained above. About one fifth of the mass of straw was lost by decomposition in the first 15 days. A chloroform treatment prevented decomposition, but Si release was unaffected. Disintegration continued throughout the experiments, with phytoliths being exposed and dissolved. Compared to the rate of release from straw into solution without soil, the release of Si into soil suspensions was increased during the first 20 days by adsorption on the soil, but was then reduced probably through the effect of Fe and Al on the phytolith surfaces. The extent of this blocking effect varied between soils and was not simply related to soil pH.     

Feed resource base for scavenging village chickens in Sri Lanka

Summary The productivity of a population of scavenging village chickens in Sri Lanka has been assessed, and the scavenging feed resource base has been measured and analysed. The laying period lasted 34 ± 13 days and the batch size was about 20 eggs. The households ate 71% of the egg production. The mean egg weight was 48 g and the mean size of a set of eggs was 9·4. The hatching percentage was 67 ± 32 and the liveweight at 70 days averaged 313 g with a range of 142 to 492, by which time 65% of the chicks hatched had died. The age at first lay averaged 211 days when the pullets weighed 1,160 g. The broody period lasted from 3 weeks to 4 months depending on whether the hen hatched eggs, and for how long she tended the brood. The laying hens were actively scavenging for most of the daylight hours. The average amount of scavenged feed per household flock per day was 550 g dry weight with a proximate composition of 9·4% crude protein, 9·2% ether extract and 5·4% crude fibre. More than 70% of the feed intake was household refuse (27% cooked rice, 30% coconut residue, 8% broken rice and 36% other scraps). The remainder was from the environment (13% grass shoots, 8% small metazoans and 7% paddy rice). Proximate analyses of crop contents, household refuse and its major components were carried out. Dietary Ca and P levels were low in the village, as were plasma levels of these minerals. On a balanced commercial diet plasma Ca was still lower than that of hybrid commercial chickens. Suggestions are made for improving the productivity of the scavenging system with no requirement for inputs, and with inputs.

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Recurso Base Para Pollos Escarbadores De Villorrio En Sri Lanka

Resumen Se estudió la productividad de una población de pollos escarbadores en Sri Lanka y la base alimenticia se analizó. El período de postura duró 34 ± 13 dias y el grupo de unidades fue de aproximadamente 20 huevos. El consumo familiar fue de 71% de la producción. El peso promedio de las unidades fue de 48 g y el tamaño promedio de un juego de huevos fue 9·4. El porcentaje de eclosión de los mismos fue de 67 ± 32 y el peso vivo a los 70 días promedió 313 g con valores extremos de 142 a 492, con un porcentaje de mortalidad a esa edad de 65%. Le edad de postura promedió 211 dias, cuando las pollonas pesaron 1160 g. El periodo de empolle fluctuó entre 3 semanas y 4 meses dependiendo de si había enclosión de huevos, o de si la gallina (s) se encluecaban. Las gallinas escarbaban constantemente durante las horas de la mañana y tarde. El promedio de alimento tomado por grupo familiar de aves fue de 550 g peso seco con una composición aproximada de 9·4% de proteina cruda, 9·2% extracto de ether y 5·4% de fibra cruda. Más de 70% de la ingestion de alimento provino de desechos de cocina (27% arroz cocinado, 30% residuos de coco, 8% arroz partido y 36% otros residuos). El resto provino de pasto, metazoas, y 7% arroz pady. El análisis reveló niveles bajos de Ca y P en el alimento y en el plasma. Bajo una dieta comercial balanceada, los niveles de calcio plasmético fueron todavia bajos, en comparación a aquellos de hibridos comerciales. Se hacen recomendaciones para mejorar la productividad de estas aves criollas con insumos y sin ellos.

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Base Des Ressources Alimentaires Des Poulets Villageois Eleves Sur Dechets Menagers Au Sri Lanka

Résumé La productivité d'une population de volailles villaqueoises se nourrissant sur les déchets ménagers au Sri Lanka a été déterminée. La base de leurs ressources alimentaires à partir de ces déchets a été mesurée et analysée. La période de ponte a duré 34 ± 13 jours et le volume a été de l'ordre de 20 oeufs. Les propriétaires ont consommé 71 p. 100 de cette production. Le poids moyen des oeufs était de 48 q et leur dimension de 9,4. Le pourcentage d'éclosion a été de 67 ± 32 et le poids vif à 70 jours de 313 g en moyenne, avec une fourchette de 142 à 492 grammes. A cette époque, 65 p. 100 des poulets couvés étaient morts. L'âge moyen à la première ponte était de 211 jours au moment où les poulettes atteignaient 1 160 q. La période de couvaison a duré de 3 semaines à 4 mois, selon que la poule pondait ou non et selon le temps passé à couver par la poule. Les pondeuses recherchaient leur nourriture très activement sur les déchets ménagers pendant le jour.La quantité moyenne de nourriture de chaque troupe individualisée par propriétaire était de 550 g, exprimée en poids sec. Sa composition approximative était la suivante: 9,4 p. 100 de protéines brutes, 9,2 p.100 d'extrait éthéré et 5,4 p. 100 de cellulose. Plus de 70 p. 100 de la prise alimentaire provenait de déchets ménagers (27 p. 100 de riz cuit, 30 p. 100 de résidu de noix de coco, 8 p. 100 de brisures de riz et 36 p. 100 d'autres restes de cuisine. Le reliquat venait de l'environnement avec 13 p. 100 de pousses d'herbe. 8 p. 100 de petits métazoaires et 7 p. 100 de riz paddy. Les auteurs ont procédé à des analyses approchées de la composition des végétaux, des refus ménagers et de leurs principaux composants. Les taux de Ca et P des rations étaient faibles dans les villages, tout comme les teneurs plasmatiques de ces minéraux. Mais, pour un régime commercial équilibré, le calcium plasmatique était encore plus bas que celui des volailles hybrides du commerce. Des suggestions sont faites pour accroître la productivité du système d'alimentation à partir des déchets ménagers avec ou sans besoins d'intrants complémentaires.

     

Gene dosage effect of the wheat Wx alleles and their interaction on amylose synthesis in the endosperm

To find out gene dose effect of each of the three homoeologous Wx genes and their interaction on the production of granule-bound starch synthase (GBSS I) and amylose biosynthesis in the endosperm, Chinese Spring and its near-isogenic waxy types were crossed reciprocally and, obtained a plant population with varying doses of each Wx gene. The amount of GBSSI was increased linearly with increasing gene dose of either of Wxloci. In each of the three Wx loci, the change in amylose content was linear up to 3 doses, with a more potent capacity ofWx-B1a at any dose. Higher level of amylose production was observed in the reciprocal F₁ grains than the expected effect of dose/s of each gene or additive effect of different allelic combination by artificially blend starches which have amylose produced by equivalent number ofWx alleles to that of relevant F₁ cross. When Wx-B1a and Wx-A1a were combined, increase in amylase content was not in proportion to increase in gene dosage. The enhanced amylase synthesis was shown by 2-gene and 3-geneinteraction, indicating that not only type of the three Wx genes and its dose but the interaction among them have significant roles in determining the amylose content. This revised version was published online in July 2006 with corrections to the Cover Date.     

Transformations of nitrogen fertilizers in soil

The effects of ¹⁵N-labelled urea, (NH₄)₂SO₄ and KNO₃ on immobilization, mineralization, nitrification and ammonium fixation were examined under aerobic conditions in an acid tropical soil (pH 4.0) and in a neutral temperate soil (pH 6.8). Urea, (NH₄)₂SO₄ and KNO₃ slightly increased net mineralization of soil organic nitrogen in both soils. There was also an apparent Added Nitrogen Interaction (ANI) i.e. added labelled NH₄-N stood proxy for unlabelled NH₄-N that would otherwise have been immobilized. So far as immobilization and nitrification were concerned, urea and (NH₄)₂SO₄ behaved very similarly in each soil. Immobilization of NO₃-N was negligible in both soils. Some of the added labelled NH₄-N was rapidly fixed, more by the temperate soil than by the tropical soil. This labelled fixed NH₄-N decreased during incubation, in contrast to labelled organic N, which did not decline.     

Bulbing responses of two cultivars of red tropical onions to photoperiod,light integral and temperature under controlled growth conditions

Summary

The effects of photoperiod, light intensity and temperature on bulb formation and bulb structure of two tropical onion cultivars were investigated. From an initial experiment it was observed that the number of true scales and sheath scales differed significantly between the cultivars ‘Red Creole’ and ‘Agrifound Dark Red’. When these two cultivars were given 11, 12 and 13 h photoperiod treatments, it was found that both cultivars needed at least 12 h photoperiod for bulb formation. Modify the R/FR ratio from 1.22 to 1.16 in the final hour of the 11 h light period did not induce bulbing. The 13 h photoperiod increased the number of true scales and decreased the number of sheath scales compared with the 12 h photoperiod in both cultivars but total scale + leaf sheath numbers remained nearly constant. When onion plants were grown under 0%, 25%, 50% and 75% shading treatments, (12 h photoperiod), only plants receiving 0% and 25% shading bulbed. Low light intensity decreased the number of true scales and increased the number of sheath scales. Four temperature regimes were compared in a growth room experiment. Plants under the 29°348C treatment bulbed within two weeks and matured within six weeks. However, plants receiving the 25°308C treatment delayed bulb initiation more than those plants receiving 17°228C and 21°268C treatments. At the lowest temperature, bigger bulbs with thick necks were produced. This may be due to changes in bulb structure since at low temperature, the number of sheath scales was increased, however the number of true scales remained relatively constant in both cultivars. Dormant leaf initials decreased with decreasing temperature while the number of secondary meristems significantly increased. The results suggest that ‘Red Creole’ was more responsive to shorter photoperiods, bulbing earlier than ‘Agrifound Dark Red’. There was no significant difference in time to bulbing in response to temperature between the two cultivars if measured by bulbing ratio however there were differences in bulb structure which suggested that ‘Red Creole’ bulbed earlier. These effects may be due to the breeding histories of the two cultivars. It is suggested that studying bulb structure may provide a useful method of interpreting onion bulbing responses.     

Nitrification and autotrophic nitrifying bacteria in acid tea soils

Pure cultures of ammonium-oxidizing, autotrophic, nitrifying bacteria were isolated from acid soils (pH range, 4.0–4.5) from tea estates in Sri Lanka (8 soils) and Bangladesh (4 soils). All the Bangladesh nitrifiers were Nitrosospira spp but the Sri Lanka isolates were identified as Nitrosolobus spp Nitrosospira spp and one species of Nitrosovibrio. Nitrite-oxidizing nitrifiers were detected in several of the soils but pure cultures were not isolated.Evidence was obtained that Nitrosospira caused nitrification in situ in an acid soil (pH 4.1). Indigenous nitrate was first eliminated from the soil by denitrification. The soil was then incubated aerobically and the nitrate formed was estimated as N₂O by gas chromatography after denitrification.     

Molecular characterization and phylogenetic analysis of Setaria digitata of Sri Lanka based on CO1 and 12S rDNA genes

The aim of the present research is to determine the phylogenetic position of Setaria digitata of Sri Lanka in the evolutionary tree of filarial worms. DNA sequences of portions of the mitochondrial genes cytochrome c oxidase subunit 1 (CO1) and small subunit ribosomal RNA (12S rDNA) were analysed. Intra-specific variation was observed in CO1 but not in 12S rDNA. Phylogenetic trees inferred from these two genes resembled one another in recognizing monophyly of Setaria. S. digitata and Setaria labiatopapillosa appear to be sister species.     

Scanning interferometric apertureless microscopy: optical imaging at 10 angstrom resolution

Interferometric near-field optical microscopy achieving a resolution of 10 angstroms is demonstrated. The scattered electric field variation caused by a vibrating probe tip in close proximity to a sample surface is measured by encoding it as a modulation in the optical phase of one arm of an interferometer. Unlike in regular near-field optical microscopes, where the contrast results from a weak source (or aperture) dipole interacting with the polarizability of the sample, the present form of imaging relies on a fundamentally different contrast mechanism: sensing the dipole-dipole coupling of two externally driven dipoles (the tip and sample dipoles) as their spacing is modulated.     

Tissue tropism of avian reoviruses is genetically determined.

Two genome segments, M2 and S1, were preferentially selected in reassortants isolated in Vero cells. Analysis with monoclonal antibodies (MAbs) against RAM-1 strain showed that the 39-kDa protein encoded by the genome segment S1 contained epitopes involved in neutralisation of virus infectivity for both Vero and chicken kidney (CK) cells. The 39-kDa protein appeared to have two major epitopes that are attachment sites for cell receptors, one interacting only with CK cell receptors and the other with both CK and Vero cell receptors but principally Vero cell receptors. These results suggest that the strain RAM-1 may have developed an epitope for Vero cell receptors owing to mutation in the S1 genome segment, but still retained the epitope responsible for infection of CK cells.