Botany
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Item Aflatoxigenic Aspergillus flavus and aflatoxin formation in selected spices during storage(2009) Rajasinghe, M.; Abeywickrama, K.P.; Jayasekera, R.Proliferation of aflatoxigenic fungi and accumulation of aflatoxins take place during storage of spices at various environmental conditions. The objective of this research was to identify the aflatoxigenic fungal species and their aflatoxin forming potential in selected spices during storage in the laboratory and refrigerator. Dilution series of spice samples namely chilli (Capsicum annum) powder, curry powder, turmeric (Curcurma longa) powder and pepper (Piper nigrum) powder (purchased from two producers) were prepared separately and the frequency of occurrence of aflatoxigenic and other fungi were assessed after plating each on Potato Dextrose Agar and incubating at ambient temperature. Aflatoxin formation of A. flavus was confirmed by growing a pure culture on a SMKY medium and identifying toxins on thin layer chromatographic plates. The presence of aflatoxins in spice samples stored at 30 ± 20C and 40C was also confirmed. Long storage of spices leads to aflatoxin production irrespective of storage temperature hence, it is advisable to consume spices such as chilli powerder, tumeric etc. within a relatively short period to avoid build up of aflatoxins.Item Development of a Job Control System to Optimize Web Traffics(2007) Fernando, S.; Dalugama, J.; Jayasekera, R.; Dassanayake, G.; Patu, V.; Minato, A.; Ozawa, S.Item Soil aeration as an ecological factor governing mangrove zonation(Springer-Netherlands, 1993) Jayasekera, R.; Lieth, H.The growth of both Rhizophora mangle L. and Rhizophora mucronata Lamk. in saline sand was highly promoted by flooded, reducing conditions in comparison to drained, aerobic conditions, showing the strong tolerance of Rhizophora seedlings to waterlogging and salinity. Under well-drained conditions, both shoot and root systems of the plants showed strongly retarded and reduced growth and a profound inverse proportionality was also found between root growth and pot volume; roots of both species were distorted and showed lack of capillary rootlets. The morphology of the root systems was greatly affected by the culture conditions providing evidence for the ecological adaptability of the Rhizophora root system to a wide variety of environmental conditions. The results obtained are in good agreement with their position in the lower, flooded zone of natural mangrove communities.Item Interelement correlations in the mangrove, Rhizophora mangle L.(Springer-Netherlands, 1993) Jayasekera, R.; Lieth, H.Assuming linear relationships between elements, some significant interelement relationships were detected in Rhizophora mangle grown over a salinity gradient. Sodium (Na) had a clear antagonistic effect on the uptake of potassium (K), whereas the uptake of chromium (Cr) and arsenic (As) seemed to be stimulated by sodium ions. A positive relationship between leaf carbon content and sodium concentration was also found. A significant negative correlation was found between the chemically related two elements, rubidium (Rb) and caesium (Cs). Owing to the competition with the absorption of K+ and NH+ 4 a negative relationship between nitrogen (N) and potassium (K) was found.Item Marine specimen banking – Archive and pollution control for the 21st century(Inderscience Publishers, 2000) Rossbach, M.; Jayasekera, R.; Kniewald, G.The oceans have in the past been extensively used as disposal sites for various kinds of waste. The world ocean – being the final sink for many natural and anthropogenic substances – is a "labile" ecosystem, which is and has for a long time been the focal point of extensive interdisciplinary research. Measurements of heavy metals and a suite of various chemical compounds in the marine environment have mostly been carried out on limited scales, within national (or regional at best) monitoring programmes (e.g. the Mussel Watch programme in the USA, or the North Sea or Baltic survey by the Northern European countries). Most of these actions were restricted to coastal waters and estuaries, which are more severely impacted by pollution than the open ocean. A long-term systematic investigation of human impact on the oceans of the world (along the global currents, the Gulf Stream or El Nino and verging on the main shipping trails) would ideally require a central survey station accompanied by an extensive banking facility capable of handling a large volume of various marine samples. As biological specimens seem to be a category highly suitable for collection and processing for analysis, one of the aims of a Marine Environmental Specimen Bank (MESB) should be to focus on such samples. Storage of authentic materials is not only valuable for real-time monitoring and basic research activities but also opens the possibility for long-term trend evaluation through retrospective analysis of well-characterised samples taken according to stringent sampling protocols.Item Improvement of Text-based E-learning Contents by Using a New Multimedia-type Web Authoring Tool - A case study from a Sri Lankan University(2007) Dassanayake, G.; Patu, V.; Fernando, S.; Jayasekera, R.; Minato, A.; Noguchi, H.; Ozawa, S.Item Effect of available rooting volume on seedling growth(Springer-Netherlands, 1993) Jayasekera, R.; Lieth, H.During the early establishment phase of Rhizophora mangle L. seedlings, a consistent positive relationship between available soil volume (varying from 2-91) and growth rate of Rhizophora manglehas been established under greenhouse conditions. As soil volume increased, root systems were larger and consistently less dense. From the results obtained it may be concluded that for optimal growth of Rhizophora mangle seedlings, the volume of soil per plant should approach that volume associated with the growth of the plants in natural habitats. Root volume appears to be a very significant index of plant growth, even under saline, flooded conditions.Item Implementation of specimen banking concepts in developing countries: First trial - Sri Lanka(Elsevier, 1993) Jayasekera, R.; Rossbach, M.The necessity to establish a small scale Environmental Specimen Bank projects in tropical countries is stressed. An example from Sri Lanka demonstrates the needs, the benefits and the prospects of such an integrated research project.Item Large scale air monitoring: Biological indicators vs. air particulate matter(2000) Rossbach, M.; Jayasekera, R.; Kniewald, G.Item Pattern of distribution of selected trace elements in the marine brown alga, Sargassum filipendula Ag. from Sri Lanka(Kluwer Academic Publishers, 1994) Jayasekera, R.Baseline concentrations together with biological variations of 29 trace elements (Ag, As, Au, Ba, Br, Cd, Ce, Co, Cr, Cs, Eu, Fe, Hf, I, Mn, Mo, Ni, Pb, Rb, Sb, Sc, Se, Sm, Sr, Tb, Th, Yb, Zn and Zr) were investigated in the brown alga, Sargassum filipendula collected from the western coast of Sri Lanka. Several elements (Co, Cr, Fe, Hf, Ni, Sc, Se, Th, Zr and the rare earth elements) were found to be enriched in S. filipendula compared to NIES No. 9 Sargasso reference material. Concentration of strontium in S. filipendula was highest at all sites. Chemical abundance of the rare earth elements decreased approximately linearly with increasing atomic numbers. The pattern of elemental distribution appears to be due to the fact that S. filipendula seems capable of concentrating high levels of trace elements under conditions of their very low availability in sea water. Concentration factors for elements in S. filipendula lie in a higher range compared with those reported in the literaure for brown algae.
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