Papers by Nimal R Chandrasena
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Capillary Electrophoresis (CE) is regarded as a powerful analytical tool that combines many advan... more Capillary Electrophoresis (CE) is regarded as a powerful analytical tool that combines many advantages of modern liquid chromatography (HPLC) with those of electrophoresis. The major advantages are: (a) high efficiency (related to decreased zone-broadening in a capillary column, fully automated instrumentation, on-line detection connected to computers supported by high efficiency software for rapid data acquisition, analysis, display, and storage,); (b) analysis speed (usually in the rage of 3-10 minutes for a complete separation); (c) operational simplicity (i.e. no pumps, column seals, guard columns or large quantities of organic solvent); (d) low to very low sample volume requirements (usually 10-15 nL of submitted sample); (e) applicability to polar and non-polar substances equally well with very little modifications; and (f) accuracy and precision in quantitative results. Among major drawback of CE is short optical length of capillary which causes a raising of detection limits. However, detection limits of an application may be improved by either improved clean-up procedures, pre-concentration of the sample, by adjustment of (larger) injection volume, or by special separation techniques such as on-column sample stacking. Paralytic shellfish poisoning (PSP) is a severe form of seafood poisoning, which results from the ingestion of the filter –feeding shellfish which contaminated with neurotoxins. At least 18 PSP toxins, which include saxitoxin (STX) and neosaxitoxin (NEO), a complex suite of sulfate and N-sulfate analogies, and their decarbamoyl derivatives, have been identified mainly produced by marine dinoflagellates and accumulated in the shellfish. The PSP toxins are poisonous because of their high-affinity binding to the sodium-ion channel of nerve cell membranes. This interferes with the propagation of electrical impulses along nerve fibres, causing muscular paralysis and death by respiratory failure. In CE, separation of analytes relies on the difference of movement of molecules under the influence of an electrical field, which means the technique is most suited for separation of charged molecules. As many of the neurotoxic paralytic shellfish poisons (PSP toxins) are charged molecules, CE has a high potential as a separation technique for their analysis in water or other matrices. Although these compounds do not contain a chromophore with significant absorptivity in the wavelength range 220-500 nm, the high sensitivity of CE combined with a UV detector (CE-UV) or a diode array detector (CE-DAD) permits detection limits of part per million levels. Development of CE-based analytical procedures to characterise and quantify neurotoxins is attractive to water industry, particularly to supplement currently available HPLC methods.
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Australians have a strong negative attitude towards weeds, and a tendency to label a large number... more Australians have a strong negative attitude towards weeds, and a tendency to label a large number of potentially useful plant resources as invasive species, which should be controlled at any cost, while ignoring considerable evidence of the use, both Indigenous by Australians and by European settlers of plants, regarded as weeds. This attitude may stem from the adjustments that early settlers had to make, to farm in an environmentally harsh continent. More recently, the application of ‘species-focused’ weed risk assessments- a field well developed in Australia, may have also contributed to the maligning of many plant taxa as ‘invaders’ in the public mind. A large number of recent publications, including government-sponsored reports, have highlighted the losses of agricultural production caused by weeds, and the threats posed by such species to biodiversity. The plants in question are mostly ‘colonisers’, which have the capacity to rapidly occupy human-modified environments. The focus in Australia has been so much on waging a protracted war on weeds that land managers have tended to overlook the potential of using these plants as resources.
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CABI eBooks, 2019
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Weeds - Journal of the Asian-Pacific Weed Science Society, Jun 30, 2021
Hewett Cottrell Watson, a British botanist and phyto-geographer, might rightfully be the first to... more Hewett Cottrell Watson, a British botanist and phyto-geographer, might rightfully be the first to apply the term 'alien' to denote 'foreign' species introduced to Britain, which successfully established at various locations in the isles with or without man's help. Botanists recognize Watson for his monumental work Cybele Britannica, written in four volumes over 12 years (1847-1859). While applying the term 'alien', along with 'natives' (indigenous species), 'denizens' (long-term residents, introduced species, who might be considered 'naturalized) and 'colonists' (species, colonizing agricultural land and habitat occupied by humans), Watson discussed in detail how difficult it is to assign 'nativeness' to any species. Stephen Troyte Dunn, who wrote 'Alien Flora of the British Isles' in 1905, partly adopted H. C. Watson's categorization of species. Both worked without much knowledge of the geological and fossil evidence of plants but agreed that all species, even 'natives', may have been immigrants sometime in the past. All of Watson and Dunn's 'alien' species have several things in common. They are all highly productive (fertile), pioneering or colonizing taxa, which can establish and thrive in disturbed environments ('artificial habitat', sensu S. T. Dunn), from which they perpetuate themselves. Knowledge about the 'foreign' components of a country's flora is ecologically important to understand how species adapt to new environments and influence others. Both Watson and Dunn emphasized the remarkable ability of some introduced to spread, unassisted by man's activities, while others, like 'shadows of men', appear to 'follow the plough'. The 'colonization process' of these highly successful plants gets them into trouble in the minds of some, who prefer to attribute other meanings, such as 'invasions' to these "foreign" species. A dip into history shows that Watson and Dunn discussed introduced plants without disparaging them. Like humans, colonizing taxa are good at what they are genetically predisposed to do, i.e., adapt and survive even under stressful environments. They are no more 'alien' than we are. They are also no more 'invasive' than we are. As one historian (Alfred Crosby) noted, these species may even help heal the wounds on the earth, torn apart by the real 'invaders'-those 'wretched ingrates' (humans).
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Journal of Developments in Sustainable Agriculture, 2007
Water and other natural resources of Bung Boraphet Wetland in Thailand have been under increasing... more Water and other natural resources of Bung Boraphet Wetland in Thailand have been under increasing pressure from over-exploitation. Sustainable management and ‘wise-use’ of the Wetland’s resources require achieving a balance between economic exploitation and conservation. Scientifically based decision support tools are vital to gain better insights into the complex interactions between the large wetland system, its contributing catchment and floodplain, and then pave the way for planning effective long-term management. This paper presents a summary of several decision support tools that we developed for Bung Boraphet. The tools are: (a) Water budget predictive model, (b) Land-use analysis using satellite imagery, and (c) Database linked Geographic Information System. From a review of literature and field studies, we identified the factors, which are having the most serious impacts on long-term sustainability of Bung Boraphet. We also conducted field studies to collect primary data on...
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Submerged aquatic plants pose problems in Australian and New Zealand waterways for navigation, fl... more Submerged aquatic plants pose problems in Australian and New Zealand waterways for navigation, flood management, bank erosion, recreation and aesthetics. Among problematic species are: Lagarosiphon (Lagarosiphon major (Ridley) Moss), Egeria (Egeria densa Planch.), Hornwort (Ceratophyllum demersum L.) and Elodea (Elodea canadensis Michx.). These species prefer clear water, where they form dense stands. The problem in controlling these plants relates to their mode of spread; the smallest viable vegetative fragment can re-establish a population. Left uncontained, these aquatic weeds are likely to fully colonize all available habitats, within a short period of time. Recent advances in application technology have allowed the safe use of aquatic herbicides in control programs. A new technique for applying the aquatic herbicideDiquat for the control of submerged aquatics has been developed in New Zealand. This method involves the use of guar gum, and formulating a Diquat gel form (Hydrogel...
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Marcel Proust, an influential 20th Century French novelist once said: “…The real voyage of discov... more Marcel Proust, an influential 20th Century French novelist once said: “…The real voyage of discovery consists not in seeking new lands but seeing with new eyes..." I commend this quote and suggest that it applies to the way we should look at weeds in this 21st Century. In this Editorial for the second issue of the new journal - Weeds - I reflect upon some ideas that have shaped our recent discourses on weeds. It seems to me that the emerging generation of weed scientists may benefit from a dip into this history. As someone said: ‘without history, man is nothing’.
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In this Editorial for the first issue of the new journal - Weeds - I reflect upon why the Asian-P... more In this Editorial for the first issue of the new journal - Weeds - I reflect upon why the Asian-Pacific Weed Science Society (APWSS) decided to launch a journal and why we decided to make it Open Access (OA).
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Alligator Weed [Alternanthera philoxeroides (Mart.) Griesb] is acknowledged as the aquatic invade... more Alligator Weed [Alternanthera philoxeroides (Mart.) Griesb] is acknowledged as the aquatic invader that poses the largest threat to Australian waterways and moist, terrestrial habitats. Despite control efforts over several decades, alligator weed is now widespread across NSW, and occurs as sporadic infestations in Queensland, ACT and Victoria, as well. It has the potential to cause losses of millions of dollars from agricultural, tourism and extractive industries across major waterways and catchments in Australia. Control methods for alligator weed include mechanical control, classical bio-control and herbicides, and combinations of these. Of these, mechanical control may provide immediate control, but also results in fragmentation and increased risks of further spread, and bio-control agents have not been particularly successful on aquatic or terrestrial infestations. Chemical control has been successful, but only short term, and several repeat applications have been required per s...
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WEEDS, 2019
The APWSS, born on 22 June 1967, is now 52 years old. It is now taking a major step forward by pu... more The APWSS, born on 22 June 1967, is now 52 years old. It is now taking a major step forward by publishing a dedicated, weed science journal - Weeds. In this Special Editorial for the journal’s inaugural issue, I am privileged to have the opportunity to reflect on the landmark events, which preceded the Society’s birth. We were not born by accident; momentous events within the discipline of Weed Science, and related fields, shaped our birth. It is appropriate, in this first issue of the new journal to acknowledge our Society’s gratitude to the three founding fathers. While providing my own views on some important challenges ahead, I recall the essence of what our founding fathers achieved, so the readers might be inspired. We stand tall today because of their vision and commitment, over five decades ago. In 2017, celebrating 50 years of existence as a professional society, we recorded the society’s achievements and contributions to Weed Science and the broad spirit in which they were...
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Weeds, 2021
Hewett Cottrell Watson, a British botanist and phyto-geographer, might rightfully be the first to... more Hewett Cottrell Watson, a British botanist and phyto-geographer, might rightfully be the first to apply the term 'alien' to denote 'foreign' species introduced to Britain, which successfully established at various locations in the isles with or without man's help. Botanists recognize Watson for his monumental work Cybele Britannica, written in four volumes over 12 years (1847-1859). While applying the term 'alien', along with 'natives' (indigenous species), 'denizens' (long-term residents, introduced species, who might be considered 'naturalized) and 'colonists' (species, colonizing agricultural land and habitat occupied by humans), Watson discussed in detail how difficult it is to assign 'nativeness' to any species. Stephen Troyte Dunn, who wrote 'Alien Flora of the British Isles' in 1905, partly adopted H. C. Watson's categorization of species. Both worked without much knowledge of the geological and fossil evidence of plants but agreed that all species, even 'natives', may have been immigrants sometime in the past. All of Watson and Dunn's 'alien' species have several things in common. They are all highly productive (fertile), pioneering or colonizing taxa, which can establish and thrive in disturbed environments ('artificial habitat', sensu S. T. Dunn), from which they perpetuate themselves. Knowledge about the 'foreign' components of a country's flora is ecologically important to understand how species adapt to new environments and influence others. Both Watson and Dunn emphasized the remarkable ability of some introduced to spread, unassisted by man's activities, while others, like 'shadows of men', appear to 'follow the plough'. The 'colonization process' of these highly successful plants gets them into trouble in the minds of some, who prefer to attribute other meanings, such as 'invasions' to these "foreign" species. A dip into history shows that Watson and Dunn discussed introduced plants without disparaging them. Like humans, colonizing taxa are good at what they are genetically predisposed to do, i.e., adapt and survive even under stressful environments. They are no more 'alien' than we are. They are also no more 'invasive' than we are. As one historian (Alfred Crosby) noted, these species may even help heal the wounds on the earth, torn apart by the real 'invaders'-those 'wretched ingrates' (humans).
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Weed Science
The effect of site of application on uptake and translocation of the butyl ester of fluazifop {(±... more The effect of site of application on uptake and translocation of the butyl ester of fluazifop {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy] phenoxy] propanoic acid} by quackgrass [Agropyron repens (L.) Beauv. # AGRRE] was investigated using 14C-labeled herbicide and intact plants. Uptake and distribution of the label were significantly greater from the abaxial than from the adaxial surface of leaves. The addition of a nonionic surfactant4 to the treatment solution increased the uptake significantly only through the adaxial surface. Uptake of 14C by the apical, middle, and basal regions of the treated leaf lamina did not differ significantly. However, movement of the 14C-label to stem areas and leaves both above and below treated leaves was greater from lamina base applications than from treatments to the lamina apex and middle. The older leaves absorbed more herbicide than did younger leaves, but the pattern of translocation did not differ. Considerably greater translocation occu...
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Weed Science
Detached leaves and whole plants of quackgrass [Agropyron repens (L.) Beauv. # AGRRE] were used t... more Detached leaves and whole plants of quackgrass [Agropyron repens (L.) Beauv. # AGRRE] were used to study uptake and translocation of butyl esters of 14C-fluazifop {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid}, with or without additional adjuvants. In the absence of adjuvants 3.2% of applied radioactivity entered detached quackgrass leaves by 6 h, and at the end of 24 h, 6.0% had penetrated. The presence of additives increased uptake by leaves significantly. In the presence of the nonionic surfactant Agral (nonyl phenol ethoxylate) at 0.2% (v/v) or the oil-additive Actipron (self-emulsifying adjuvant oil) at 2.0% (v/v), 17.2 and 12.9% of applied radioactivity, respectively, entered the leaves by 24 h. Evidence of dependence of phloem translocation of the radioactivity on source-sink relationships of the plant was obtained in the studies with whole plants. Translocation measured up to 7 days after treatment showed that radioactivity was concentrated in are...
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Weed Science
The phytotoxicity of the butyl ester of fluazifop to quackgrass was enhanced by the addition of a... more The phytotoxicity of the butyl ester of fluazifop to quackgrass was enhanced by the addition of a nonionic surfactant and an oil additive either alone or in mixture to the spray solution. The enhancement caused by the surfactant was consistently greater than that caused by the oil additive. A higher level of quackgrass control was achieved at the carrier volumes of 100, 200, or 400 L/ha, than at 800 L/ha. Quackgrass growth inhibition was greater following application of small herbicide droplets which averaged 0.25 μl compared to larger herbicide droplets at each herbicide application rate. When droplet concentration was varied and different doses of the herbicides applied to plants, no significant differences were noted at the highest dose. However, at intermediate dose treatments, the least concentrated droplets (2.5 μg/μl) were most phytotoxic. Herbicide droplets placed at basal areas of leaves were more phytotoxic than when placed at lamina apices and middle areas. This effect wa...
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Papers by Nimal R Chandrasena