Search

Contamination and exposure to textile dye wastewater are environmental issues of grave concern, especially in developing countries. The use of advanced technologies to remediate wastewater is not economical for small- and medium-sized industries. An environmentally friendly and economical method was developed to adsorb dyes from wastewater using a composite material, prepared by the sol–gel method. The surface area was 18.16 m2/g and the pH at the point of zero charge (pHPZC) was 4.2. The peak shifts in Fourier transform infrared spectra upon adsorption indicated the functional groups involved in adsorption while scanning electron microscopic images indicated that exfoliated and intercalated polymer layer silicate structures are present in the composite. The composite dose of 0.20 g adsorbed over 90% of fuchsine and methylene blue dyes after 240 min and 330 min, respectively. The experimental data of fuchsine adsorption agreed with the Langmuir–Freundlich combined isotherm while methylene blue adsorption data obeyed the Freundlich isotherm alone. Fuchsine dye forms Hydrogen (H)-bonds and H–π interactions with the adsorbent surface, and H-bonds and π–π interactions between the dye molecules to form multilayers. The methylene blue forms H–π interactions with the adsorbent surface. The composite can remove negatively charged dyes since the adsorption surface is positively charged even at pH 7. The composite dose of 0.20 g reduced the absorbance of dyes in wastewater within 6 h of agitation. This shows that the adsorbent has the potential to remove pigment dyes and direct dyes present in industrial wastewater.

Phosphorus is an essential plant nutrient required by all living organisms and global phosphate resources, being finite, are expected to last another 125 years. This study investigated a sustainabl...

Background Assessing the vulnerability of an infectious disease such as dengue among endemic population is an important requirement to design proactive programmes in order to improve resilience capacity of vulnerable communities. The current study aimed to evaluate the climate change induced socio-economic vulnerability of local communities to dengue in Colombo and Kandy districts of Sri Lanka. Methods A total of 42 variables (entomological, epidemiological, meteorological parameters, land-use practices and socio-demographic data) of all the 38 Medical Officer of Health (MOH) areas in the districts of Colombo and Kandy were considered as candidate variables for a composite index based vulnerability assessment. The Principal Component Analysis (PCA) was used in selecting and setting the weight for each indicator. Exposure, Sensitivity, Adaptive Capacity and Vulnerability of all MOH areas for dengue were calculated using the composite index approach recommended by the Intergovernmental Panel on Climate Change. Results Out of 42 candidate variables, only 23 parameters (Exposure Index: six variables; Sensitivity Index: 11 variables; Adaptive Capacity Index: six variables) were selected as indicators to assess climate change vulnerability to dengue. Colombo Municipal Council (CMC) MOH area denoted the highest values for exposure (0.89: exceptionally high exposure), sensitivity (0.86: exceptionally high sensitivity) in Colombo, while Kandy Municipal Council (KMC) area reported the highest exposure (0.79: high exposure) and sensitivity (0.77: high sensitivity) in Kandy. Piliyandala MOH area denoted the highest level of adaptive capacity (0.66) in Colombo followed by Menikhinna (0.68) in Kandy. The highest vulnerability (0.45: moderate vulnerability) to dengue was indicated from CMC and the lowest indicated from Galaha MOH (0.15; very low vulnerability) in Kandy. Interestingly the KMC MOH area had a notable vulnerability of 0.41 (moderate vulnerability), which was the highest within Kandy. Conclusions In general, vulnerability for dengue was relatively higher within the MOH areas of Colombo, than in Kandy, suggesting a higher degree of potential susceptibility to dengue within and among local communities of Colombo. Vector Controlling Entities are recommended to consider the spatial variations in vulnerability of local communities to dengue for decision making, especially in allocation of limited financial, human and mechanical resources for dengue epidemic management.

Background. Early detection of dengue epidemics is a vital aspect in control programmes. Predictions based on larval indices of disease vectors are widely used in dengue control, with defined threshold values. However, there is no set threshold in Sri Lanka at the national or regional levels for Aedes larval indices. Therefore, the current study aimed at developing threshold values for vector indices in two dengue high-risk districts in Sri Lanka. Methods. Monthly vector indices (House Index [HI], Container Index [CI], Breteau Index for Aedes aegypti [BIagp], and Ae. albopictus [BIalb]), of ten selected dengue high-risk Medical Officer of Health (MOH) areas located in Colombo and Kandy districts, were collected from January 2010 to June 2019, along with monthly reported dengue cases. Receiver Operating Characteristic (ROC) curve analysis in SPSS (version 23) was used to assess the discriminative power of the larval indices in identifying dengue epidemics and to develop thresholds for the dengue epidemic management. Results. Only HI and BIagp denoted significant associations with dengue epidemics at lag periods of one and two months. Based on Ae. aegypti, average threshold values were defined for Colombo as Low Risk (2.4≤BIagp<3.8), Moderate Risk (3.8≤BIagp<5), High Risk (BIagp≥5), along with BIagp 2.9≤BIagp<4.2 (Low Risk), 4.2≤BIagp<5.3 (Moderate Risk), and BIagp≥5.3 (High Risk) for Kandy. Further, 5.5≤HI<8.9, 8.9≤HI<11.9, and HI≥11.9 were defined as Low Risk, Moderate Risk, and High Risk average thresholds for HI in Colombo, while 6.9≤HI<9.1 (Low Risk), 8.9≥HI<11.8 (Moderate Risk), and HI≥11.8 (High Risk) were defined for Kandy. Conclusions. The defined threshold values for Ae. aegypti and HI could be recommended as indicators for early detection of dengue epidemics and to drive vector management activities, with the objective of managing dengue epidemics with optimal usage of financial, technical, and human resources in Sri Lanka.

Climate change has pushed the natural limits of our environment, creating extreme weather events that are more frequent and more intense in certain locations around the globe. There is evidence of increasing trends in temperature extremes in most countries of South Asia, while in a few regions, temperature extremes have been decreasing. Heatwaves have intensified, which has contributed to accelerating drought and extreme flood events in most South Asian countries. Overall changes in rainfall and temperature have led to alterations in water availability in this region. With few exceptions, the general phenomenon in most South Asian countries is that rainfall intensity has increased, but with a reduced number of wet days. Studies that associate rainfall and temperature in the region of South Asia are scarce and rainfall extremes have been studied more extensively than temperature extremes. In fact, temperature trends are spatially less coherent than rainfall trends in most south Asian countries. It is more likely correlated for the teleconnection and South Asian climate for influencing the temperature and rainfall pattern, rather than any other factors. When it comes to trend estimations, statistical slope detection metrics, such as simple linear regression, have been commonly used to detect and quantify mean trends for countries in the regions of South Asia. However, application lacks in usage of robust nonparametric statistical tests to quantify temperature and rainfall extremes in many countries of South Asia. Statistical downscaling is recommended for better prediction accuracy as well as to find spatial coherence in trends.

Pollution of surface water from textile dyes affects the quality of drinking and farming water, besides negatively changing the aesthetic environment. While living plants can remediate textile dyes through phytoremediation, the dried biomass of plants can also be used as adsorbents. This is by virtue of the functional groups on the biomass, which can bind to cationic or anionic components of the dye. This chapter reviews the sorption methods available from plants and their biomass to cost-effectively treat wastewaters from textile industries. Plants use a variety of pathways to detoxify dyes within the plant tissues including enzymatic breakdown and biotransformation to tolerate the toxic effects. The biomass of plants is characterized by organic functional groups able to bind with the charged surfaces of the dyes and thereby facilitate their removal by sorption. This chapter would discuss the potential of using plants to remove dye effluents through various mechanisms.

Background: Assessing the vulnerability of an infectious disease such as dengue among endemic population is an important requirement to design proactive programmes in order to improve resilience capacity of vulnerable communities. Despite the significance in decision making process especially for rational resource allocation, the recognition of actual burden of dengue and the vulnerability towards dengue, has been limitedly addressed in many countries including Sri Lanka, due to deficiencies in a holistic methodology. Methods: A total of 42 variables (entomological, epidemiological, meteorological parameters, land-use practices and socio-demographic data) of all the 38 Medical Officer of Health (MOH) areas in the districts of Colombo and Kandy were considered as candidate variables for a composite index based vulnerability assessment. The Principal Component Analysis (PCA) was used in selecting and setting the weight for each indicator. Exposure, Sensitivity, Adaptive Capacity and Vulnerability of all the MOH areas for dengue incidence were calculated. Results: Out of 42 candidate variables, only 23 parameters (Exposure Index: 6 variables; Sensitivity Index: 11 variables; Adaptive Capacity Index: 6 variables) were selected as indicators to assess climate change vulnerability to dengue. Colombo Municipal Council (CMC) MOH area denoted the highest values for exposure (0.89: exceptionally high exposure), sensitivity (0.86: exceptionally high sensitivity) in the district of Colombo, while Kandy Municipal Council (KMC) area reported the highest exposure (0.79: high exposure) and sensitivity (0.77: high sensitivity) in Kandy. Piliyandala MOH area denoted the highest level of adaptive capacity (0.66) in the district of Colombo followed by Menikhinna (0.68) in Kandy. The highest vulnerability (0.45: moderate vulnerability) to dengue was indicated from CMC and the lowest indicated from Galaha MOH (0.15; very low vulnerability) in Kandy. Interestingly the Kandy Municipal Council MOH area had a notable vulnerability of 0.41 (moderate vulnerability), which was the highest within Kandy. Conclusions: In general, vulnerability for dengue was relatively higher within the MOH areas of Colombo, than in Kandy, suggesting a higher degree of potential susceptibility to dengue within and among local communities of Colombo. The Vector Controlling Entities (VCE) are recommended to consider the spatial variations in vulnerability of local communities to dengue for decision making, especially in allocation of limited financial, human and mechanical resources for dengue epidemic management

Background Comprehensive understanding of risk factors related to socio-economic and demographic status and knowledge, attitudes and practices (KAP) of local communities play a key role in the design and implementation of community-based vector management programmes, along with the identification of gaps in existing control activities. Methods A total of 10 Medical Officers of Health (MOH) areas recording high dengue incidence over the last five years were selected from Colombo (n = 5) and Kandy (n = 5) Districts, Sri Lanka. From each MOH area, 200 houses reporting past dengue incidence were selected randomly as test group (n = 1000 for each district) based on the dengue case records available at relevant MOH offices. Information on socio-economic and demographic status and knowledge, attitudes and practices were gathered using an interviewer administered questionnaire. The control group contained 200 households from each MOH area that had not reported any dengue case and the same questionnaire was used for the assessment (n = 1000 for each district). Statistical comparisons between the test and control groups were carried out using the Chi-square test of independence, cluster analysis, analysis of similarities (ANOSIM) and multi-dimensional scaling (MDS) analysis. Results Significant differences among the test and control groups in terms of basic demographic and socio-economic factors, living standards, knowledge, attitude and practices, were recognized (P < 0.05 at 95% level of confidence). The test group indicated similar risk factors, while the control group also shared more or less similar characteristics as depicted by the findings of cluster analysis and ANOSIM. Findings of the present study highlight the importance of further improvement in community education, motivation and communication gaps, proper coordination and integration of control programmes with relevant entities. Key infrastructural risk factors such as urbanization and waste collection, should be further improved, while vector controlling entities should focus more on the actual conditions represented by the public on knowledge, attitudes and personal protective practices. Conclusions The design of flexible and community friendly intervention programmes to ensure the efficacy and sustainability of controlling dengue vectors through community based integrated vector management strategies, is recommended.

Background Socio-economic, demographic factors and Knowledge Attitude Practices (KAPs) have been recognized as critical factors that influence the incidence and transmission of dengue epidemics. However, studies that characterize above features of a risk free or low risk population are rare. Therefore, the present study was conducted to characterize the household related, demographic, socio-economic factors and KAPs status of five selected dengue free communities. Method An analytical cross-sectional survey was conducted on selected demographic, socio-economic, household related and KAPs in five selected dengue free communities living in dengue risk areas within Kandy District, Central Province, Sri Lanka. Household heads of 1000 randomly selected houses were interviewed in this study. Chi-square test for independence, cluster analysis and Principal Coordinates (PCO) analysis were used for data analysis. Results Knowledge and awareness regarding dengue, (prevention of the vector breeding, bites of mosquitoes, disease symptoms and waste management) and attitudes of the community (towards home gardening, composting, waste management and maintenance of a clean and dengue free environment) are associated with the dengue free status of the study populations. Conclusions The vector controlling authorities should focus on socio-economic, demographic and KAPs in stimulating the community to cooperate in the integrated vector management strategies to improve vector control and reduce transmission of dengue within Kandy District. Electronic supplementary material The online version of this article (10.1186/s12879-018-2995-y) contains supplementary material, which is available to authorized users.

Removal of Pb(II) from an aqueous environment using biosorbents is a cost-effective and environmentally benign method. The biosorption process, however, is little understood for biosorbents prepared from plant materials. In this study, the biosorption process was investigated by evaluating four adsorption models. A fixed-bed column was prepared using a biosorbent prepared from the aquatic plant Hydrilla verticillata. The effect of bed height and flow rate on the biosorption process was investigated. The objective of the study was to determine the ability of H. verticillata to biosorb Pb(II) from an aqueous environment and to understand the process, through modeling, to provide a basis to develop a practical biosorbent column. Experimental breakthrough curves for biosorption of 50 mg L−1 aqueous Pb(II) using a fixed-bed column with 1.00 cm inner diameter were fitted to the Thomas, Adams-Bohart, Belter, and bed depth service time (BDST) models to investigate the behavior of each model according to t...

The extent of biosorption of Pb(II) and Ni(II) by dried leaves of the fern Asplenium nidus depends on experimental conditions, such as initial pH, initial concentration, contact time and shaking speed. Kinetic data were fitted to pseudo first order, pseudo second order, intraparticle diffusion and Elovich models. Isotherm data were fitted to two-parameter and three-parameter isotherm models. A. nidus adsorbed 58% of Ni(II) and 95% of Pb(II) after 30 min and 75 min, respectively, under the experimental conditions provided. The protonated biosorbent adsorbed 75% of Ni(II) after 30 min. Kinetic data fitted the pseudo second order model and the intraparticle diffusion model showed that intraparticle diffusion is not the only process that governs the adsorption process. Isotherm studies showed that Langmuir–Freundlich isotherm model explains the adsorption process well.

Extensive work has been reported on genetic transformation of microorganisms and model plant species for heavy metal remediation. The genes used for transformation belong to metallothioneins, glutathiones, phytochelatins, and membrane transporters. In vitro experiments form the core process of creating transgenic plants, establishing successful transformations and preliminary testing of the transformant. Few studies have progressed from in vitro experiments to field testing. The release of transgenics to the environment is a cause of concern for the public and legislators. The major concerns are gene flow of the transgene into wild or crop relatives and their ability to interbreed and thus enter the food chain. These challenges can be overcome by choosing sterile or vegetatively propagated species, self-pollinated plants, and perennial species with a long generation interval. These can effectively address the concerns of gene flow from transformed plants into the existing gene pool, and provide a new generation of phytoremediators.

Background Larval indices such as Premise Index (PI), Breteau Index (BI) and Container Index (CI) are widely used to interpret the density of dengue vectors in surveillance programmes. These indices may be useful for forecasting disease outbreaks in an area. However, use of the values of these indices as alarm signals is rarely considered in control programmes. Therefore, the current study aims to propose threshold values for vector indices based on an empirical modeling approach for the Kandy District of Sri Lanka. Methods Monthly vector indices, viz PI, BI and CI, for Aedes aegypti and Aedes albopictus, of four selected dengue high risk Medical Officer of Health (MOH) areas in the Kandy District from January 2010 to August 2017, were used in the study. Gumbel frequency analysis was used to calculate the exceedance probability of quantitative values for each individual larval index within the relevant MOH area, individually and to set up the threshold values for the entomological management of dengue vectors. Results Among the study MOH areas, Akurana indicated a relatively high density of both Ae. aegypti and Ae. albopictus, while Gangawata Korale MOH area had the lowest. Based on Ae. aegypti, threshold values were defined for Kandy as low risk (BIagp > 1.77), risk (BIagp > 3.23), moderate risk (BIagp > 4.47) and high risk (BIagp > 6.23). In addition, PI > 6.75 was defined as low risk, while PI > 9.43 and PI>12.82 were defined as moderate and high risk, respectively as an average. Conclusions Threshold values recommended for Ae. aegypti (primary vector for dengue) along with cut-off values for PI (for Ae. aegypti and Ae. albopictus), could be suggested as indicators for decision making in vector control efforts. This may also facilitate the rational use of financial allocations, technical and human resources for vector control approaches in Sri Lanka in a fruitful manner. Electronic supplementary material The online version of this article (10.1186/s13071-018-2961-y) contains supplementary material, which is available to authorized users.

Textile dye contamination of waterways is a major environmental and health issue related to small and medium size enterprises in developing countries. Conventional decontamination techniques are expensive for these enterprises. Biosorption is cost effective, simple and an efficient method for decontamination. An understanding of the adsorption mechanism under optimum reaction conditions would enable the efficient utilization of the biosorbent. We determined the adsorption behaviour of a biosorbent prepared from the ornamental fern A. nidus and fuchsine dye under different experimental parameters. Kinetic data were fitted to adsorption kinetic models and adsorption diffusion models. Isotherm data were fitted to two-parameter and three-parameter isotherm models. This paper postulates a mechanism for the adsorption of fuchsine dye onto the biosorbent using kinetic, isotherm and thermodynamic data. The biosorbent adsorbed 88% of fuchsine after 150 min, under the experimental conditions. The adsorption percentage increased when the biomass dose was increased from 0.1 g to 0.2 g and remained the same thereafter. Kinetic data showed that the pseudo second order kinetic model is more applicable and both intraparticle diffusion and liquid film diffusion control the rate of the adsorption process. Isotherm studies showed that the Langmuir–Freundlich isotherm model explains the adsorption process well with a maximum adsorption capacity of 12.95 mg g−1 of dry biosorbent. Thermodynamic parameters suggest that the adsorption is a spontaneous exothermic process with an enthalpy change of −59.26 kJ mol−1 and entropy change of −0.09 kJ mol−1 K−1. It can be concluded that the adsorption is governed by diffusion through the liquid film and within the biosorbent particle surface forming covalent and hydrogen bonding interactions between fuchsine molecules and functional groups of the adsorbent and π–π electron interactions between phenyl rings of the dye molecule.

This study was aimed to investigate the potential of biochar (BC), a waste byproduct of a bioenegy industry, Sri Lanka, as a soil amendment to immobilize and reduce the phytotoxicity of Cr in tannery waste-polluted soil (TWS). The TWS and bioenergy waste BC were characterized for physio-chemical parameters. A pot experiment was conducted by adding three BC application rates, 1, 2.5, and 5 % (w/w) to investigate the immobilizing capacity and bioaccumulation of chromium (Cr) in tomato plants (Lycopersicon esculentum L.). Soils and plants were digested via microwave digestion and analyzed for total Cr. Further, sequential extraction was conducted to assess the fractionation of Cr before and after the application of bioenergy waste BC on TWS. The total Cr concentration in TWS was 12,285 mg/kg. The biomass of tomato plants grown in the 5 % BC amendment doubled compared to the biomass in BC-unamended soil. Bioaccumulation of Cr in plants grown in 5 % BC-amended TWS showed a decrease by 97 % compared to that of the BC-unamended soil. The CaCl2 extractability of Cr indicated that the bioavailability of Cr in the 5 % BC amendment has decreased by 68 % compared to the control. Sequentially extracted Cr in the exchangeable fraction decreased by 98 % in the 5 % BC amendment. Pore diffusion, and adsorption via π-π electron donor-acceptor interactions were the primary mechanisms to be involved in the Cr retention in BC. Results suggested that the addition of BC to TWS reduces the mobility, bioavailability, and phytotoxicity of Cr in tomato plants.

Climate is the key driver of diversity of life in ecosystems. Changes in the climate, would not only alter the spatial distribution of species but also facilitate some of the non-native species to become invasive. This would further imbalance the status quo of native species and may bring about irreversible changes in some ecosystems imposing large economic costs for their management. Few researchers have addressed the issue of the interaction of climate change and invasive species in developing countries. We review the ecological impacts of invasive alien flora on the environment and the necessity to assess the economics of these impacts, particularly in developing countries. The potential implications of climate change on invasive alien flora relevant to Sri Lanka are discussed, highlighting how disturbances to ecosystems during climate change would facilitate the dispersal, establishment and spread of these invasive species and result in a change in the species distribution of native flora within ecosystems. The management of invasive alien species is already formulated for Sri Lanka. We draw attention to how climate change aspects should be incorporated into these management strategies. Important aspects to be considered are assessment of risk, targeting ecosystems vulnerable to climate change and mapping to monitor the location and progress of invasive flora.Ceylon Journal of Science (Bio. Sci.) 43 (2): 1-15, 2014

In this study, we used a comprehensive set of statistical metrics to investigate the historical trends in averages and extremes of rainfall and temperature in Sri Lanka. The data consist of 55 years (1961–2015) of daily rainfall, maximum temperature (Tmax), and minimum temperature (Tmin) records from 20 stations scattered throughout Sri Lanka. The linear trends were analyzed using the nonparametric Mann–Kendall test and Sen–Theil regression. The prewhitening method was first used to remove autocorrelation from the time series, and the modified seasonal Mann–Kendall test was then applied for the seasonal data. The results show that, during May, 15% of the stations showed a significant decrease in wet days, which may be due to the delayed southwest monsoon (SWM) to Sri Lanka. A remarkable increase in the annual average temperature of Tmin and Tmax was observed as 70% and 55% of the stations, respectively. For the entire period, 80% of the stations demonstrated statistically significant increases of Tmin during June and July. The daily temperature range (DTR) exhibited a widespread increase at the stations located within the southwestern coast region of Sri Lanka. Although changes in global climate, teleconnections, and local deforestation in recent decades at least partially influence the trends observed in Sri Lanka, a formal trend attribution study should be conducted.

The potential of nonliving biomass of Hydrilla verticillata to adsorb Pb(II) from an aqueous solution containing very low concentrations of Pb(II) was determined in this study. Effects of shaking time, contact time, biosorbent dosage, pH of the medium, and initial Pb(II) concentration on metal-biosorbent interactions were studied through batch adsorption experiments. Maximum Pb(II) removal was obtained after 2 h of shaking. Adsorption capacity at the equilibrium increased with increasing initial Pb(II) concentration, whereas it decreased with increasing biosorbent dosage. The optimum pH of the biosorption was 4.0. Surface titrations showed that the surface of the biosorbent was positively charged at low pH and negatively charged at pH higher than 3.6. Fourier transform infrared (FT-IR) spectra of the biosorbent confirmed the involvement of hydroxyl and C˭O of acylamide functional groups on the biosorbent surface in the Pb(II) binding process. Kinetic and equilibrium data showed that the adsorption...

Many countries are in search of more effective and sustainable methods for controlling dengue vectors, due to undeniable inefficiencies in chemical and mechanical vector control methods. Bio-control of vectors by copepods is an ideal method of using interactions in the natural ecosystem for vector management, with minimum consequences on the environment. Current study determined the predatory efficacy of five locally abundant copepod species on, Aedes larvae under laboratory conditions. Copepods were collected from the pre-identified locations within the districts of Gampaha and Kandy, and identified morphologically. Individual species of copepods were maintained as separate colonies with Paramecium culture and wheat grain as supplementary food. Five adult copepods of each species was introduced into separate containers with 200 larvae (1st instar) of Aedes aegypti. Number of larvae survived in containers were enumerated at 3 hour intervals within a duration of 24 hours. Each experiment was repeated five times. The same procedure was followed for Ae. albopictus. Significance in the variations among predation rates was evaluated with General Linear Modelling (GLM) followed by Tukey’s pair-wise comparison in SPSS (version 23). Significant variations in predation rates of studied copepod species were reported (p

The induction of secondary embryos in androgenic and zygotic embryos of Datura metel (L.) (Solanaceae) was investigated by excising their shoot and root meristems and culturing the hypocotyls on Nitsch medium. Androgenic embryos produced secondary embryos on the hypocotyl. Histological sections showed secondary embryo development was independent of maternal tissue with no connection to the maternal vascular system. The zygotic embryos produced shoot buds and adventitious roots from the cut surface. Shoot buds had vascular connections with the maternal tissue. Excision of both meristems produced more secondary embryos than excision of the apical meristem alone. Excision of apical meristems in embryogenically competent immature embryos and their in vitro culture could potentially produce secondary embryos on the hypocotyls. The significance of these results is the clonal multiplication of the primary embryo at an early stage of embryo development. The meristem excision steps are easily performed under sterile conditions.

Globally, ultramafic outcrops are renowned for hosting floras with high levels of endemism, including plants with specialised adaptations such as nickel or manganese hyperaccumulation.[br/] Soils derived from ultramafic regoliths are generally nutrient-deficient, have major cation imbalances, and have concomitant high concentrations of potentially phytotoxic trace elements, especially nickel. The South and Southeast Asian region has the largest surface occurrences of ultramafic regoliths in the world, but the geoecology of these outcrops is still poorly studied despite severe conservation threats. Due to the paucity of systematic plant collections in many areas and the lack of georeferenced herbarium records and databased information, it is not possible to determine the distribution of species, levels of endemism, and the species most threatened.[br/] However, site-specific studies provide insights to the ultramafic geoecology of several locations in South and Southeast Asia. The geoecology of tropical ultramafic regions differs substantially from those in temperate regions in that the vegetation at lower elevations is generally tall forest with relatively low levels of endemism. On ultramafic mountaintops, where the combined forces of edaphic and climatic factors intersect, obligate ultramafic species and hyperendemics often occur. Forest clearing, agricultural development, mining, and climate change-related stressors have contributed to rapid and unprecedented loss of ultramafic-associated habitats in the region.[br/] The geoecology of the large ultramafic outcrops of Indonesia's Sulawesi, Obi and Halmahera, and many other smaller outcrops in South and Southeast Asia, remains largely unexplored, and should be prioritised for study and conservation.

In the aquaculture industry of Sri Lanka, Cryptocoryne and Echinodorus species are important aquatic plants. In the absence of a regular supply due to lack of effective propagation methods, Cryptocoryne species are indiscriminately harvested from the wild to supply to the export market. The threat on the species is further compounded by the loss of their rainforest habitats. Out of the ten endemic Cryptocoryne species that occur in Sri Lanka, nine are classified as "Highly Threatened" species in the Red List of International Union for the Conservation of Nature. Echinodorus cordifolius is not found in the wild but is popular in aquaria. In order to overcome the problems of species loss and inadequate supply to the local and foreign markets, an in vitro micro-propagation method was developed for both these species. Due to the difficulty in obtaining axenic cultures from these species, rhizome segments were used to induce axillary bud growth and subsequent shoot multiplication. Shoot buds were induced from rhizome segments of C. wendtii cultured on a Murashige and Skoog (MS) basal medium supplemented with 11 – 133 µM benzyladenine (BA) and 13.4 µM naphthalene acetic acid (NAA). The induced shoots were separated after 21 days and sub-cultured twice every 14 days on MS medium, which increased the shoot multiplication. E. cordifolius responded positively to a combination of 24.6 µM N-isopentenyladenine (2iP) and 2.68 µM NAA, while 2iP alone did not induce shoots. Two sub-cultures at 14 day intervals increased the shoot multiplication. Rooting was induced in both species by culturing the shoots in ½ MS liquid medium with indole butyric acid (IBA). Acclimatization was done in a humid growth chamber for one week and the plantlets were gradually transferred to the green house. All the plantlets rooted and survived in the green house. DOI: 10.4038/sljas.v12i0.2216 Sri Lanka J. Aquat. Sci. 12 (2007): 89-101

Biology is generally accepted as a mainstream scientific discipline. However, philosophers of science have questioned the scientific method applied in biological sciences, specifically in evolutionary biology, ever since Karl Popper formulated his principle of falsification. Thus the only major theory in biology, Darwin's theory of evolution, was referred to by Popper as a metaphysical programme. He contended that the theory of evolution is a tautology and laws (if any) in the biological sciences should be unrestricted and universal. As biologists since then have pointed out, biology is a unique science, which requires unique methods to explain its phenomena. The principle of falsification and its application to biological sciences, the uniqueness of biology as a science necessitating different and equally valid scientific methods are discussed. doi: 10.4038/cjsbs.v36i2.487 Cey. J. Sci. (Bio. Sci.) 36 (2): 126-133, 2008

Androgenesis may be induced in plants by a stress application on microspores or anthers. Temperature stress treatments have generally been confined to a single temperature regime (above or below ambient) lasting from a few hours to days. We introduced a gradient with two temperature pulses (30 s each) in the stress application on anthers of Datura metel L. by stepping the temperature up and down for a total period of 60 s. Anthers were immersed in sterile water preheated and cooled to the desired temperature and cultured on Nitsch medium. The temperature pulse gradient significantly improved androgenesis compared to single temperature treatments, resulting in increased mean embryogenesis of 128% over control for 45°/15°C, 110% for 45°/10°C, 113% for 40°/10°C and 96% for 45°/5°C. The 45°/10°C gradient also significantly increased the number of dividing microspores observed, after 14 days of anther culture. Besides the differential of the gradient, the temperature limit was important, with anthers not tolerating temperatures beyond 45°C. The temperature pulse gradient applied at an early stage of culture may increase the window of competency of microspores for androgenesis.

The oil of Adenanthera pavonina L. seeds was analysed by chromatographic and instrumental means. The oil was found to be rich in neutral lipids (86.2%), and low in polar lipids (13.8%). The neutral lipids consisted mainly of triacylglycerols (64.2%). Unsaturated fatty acids were found as high as 71%, while the percentage of saturated fatty acids was only 29%. GC and GC/MS analyses revealed linoleic, oleic and lignocerotic acid to be predominant among all fatty acids in the A. pavonina oil, whereas stigmasterol was the major steroid identified within this study. Subsequently, the oil was used for preparation of submicron oilin- water (o/w) lipid emulsions. Lipid emulsions were formulated by using soybean lecithin (SL) to investigate their particle size, Zeta potential and stability at the different oil and SL ratios. The results obtained indicate possible applications of the tested oil in pharmaceutical and medical fields as drug and cosmetic active ingredient carriers.

Ageratum conyzoides L. is an annual herb in the tropics and subtropics whose extracts are known to possess pharmacological and biocidal activity. We report on the bioactivity of a secondary metabolite (a chromene) isolated from the shoots ofA. conyzoides against some plant pathogenic fungi. Organic solvent extracts from the shoots were tested for antifungal activity against the plant pathogenic fungiRhizoctonia solani, Sclerotium rolfsii, Botryodiplodia theobromae, Phomopsis theae andFusarium species growingin vitro on potato dextrose agar medium. The cruden-hexane extract completely inhibited the growth ofR. solani andS. rolfsii. Then-hexane extract was chromatographed over a column of silica gel followed by activity-guided fractionation to give an antifungal principle. Structure elucidation by detailed analysis of1H,13C NMR and mass spectroscopy identified the active compound as precocene II. The growth ofR. solani andS. rolfsii was completely inhibited by precocene II at a concentration of 80–100 ppm. The sclerotia ofR. solani andS. rolfsii were also completely suppressed by 150 ppm of precocene II. Sub-culture of these inhibited fungi onto precocene II-free medium restored growth of the fungus, indicating that precocene II is fungistatic. Crude or refined extracts fromA. conyzoides offer the possibility of biocontrol of plant pathogenic fungi.

Compared with serpentine floras of Southeast Asia, the serpentine vegetation of Sri Lanka is impoverished in regard to serpentine endemics and nickel hyperaccumulators. All species so far documented from the serpentine outcrops of Sri Lanka also have non-serpentine populations; it is unclear whether the serpentine populations are physiologically distinct and deserve ecotypic recognition. We conducted a preliminary study to examine whether serpentine and non-serpentine populations of Fimbristylis ovata represent locally adapted ecotypes by investigating their growth and potential for nickel uptake and tolerance under greenhouse conditions. Although both populations of F. ovata showed a similar growth pattern in serpentine soil during short-term exposure (21 days), the non-serpentine population was unable to survive in serpentine soil under long-term exposure (4 months). Both populations were able to uptake nickel from serpentine soil during short-term exposure (21 days). The serpentine population, however, translocated significantly more nickel from its roots to shoots (translocation factor 0.43) than the non-serpentine population (translocation factor 0.29). Our preliminary investigations suggest that the serpentine and non-serpentine populations of F. ovata may be locally adapted to their respective soils. However, additional studies are required to determine whether the populations deserve ecotypic recognition.

Microspore-derived embryos (MDEs) of Brassica napus were used to study the influence of sucrose, jasmonic acid (JA), and abscisic acid (ABA) on dry weight and total glucosinolate (GSL) content as well as on specific GSLs. An improved procedure was developed to enable the detection of alkenyl and indole GSLs in single MDEs although they were cultured in medium containing 13% sucrose, where the accumulation of GSL is very low. A sucrose content of 2% and below in the culture medium of the embryos was necessary to significantly increase the total GSL content in embryos of three different rapeseed cultivars. The increase in total GSL content was caused predominantly by higher contents of the indole GSL glucobrassicin (GBC). Contents of 4-hydroxy-3-indolyl glucosinolate (4OH), neoglucobrassicin (NEO), and 4-methoxyglucobrassicin (4ME) were also increased. Alkenyl GSL content remained largely unaffected and increased significantly only in embryos cultured at the lowest tested sucrose concentration of 1%. Growing the embryos in the presence of JA did not change the alkenyl GSL content but led to a 7-fold increase in the indole GSL content. Significant increases were found for GBC, 4OH and NEO, whereas 4ME content was not affected. The JA treatment did not affect the morphology or dry weight of the MDEs. In contrast, a treatment with ABA significantly reduced the dry weight and the indole GSL content of the embryos. In the combined JA and ABA treatment, the stimulative effect of JA on indole GSL biosynthesis could not override the inhibitory effect of ABA on growth and indole GSL biosynthesis of the embryos.

Microspore derived embryoids and plantlets derived from these embryoids synthesized glucosinolates in vitro. The embryoids produced glucosinolates 24 days after culture of the microspores, upon transferring the embryoids from medium containing 13% sucrose to 3%. With time, the indole glucosinolates were predominantly synthesized, independent of the glucosinolate profile of the parental seeds. Alkenyl glucosinolates were synthesized, particularly by the high glucosinolate genotypes. The alkenyl glucosinolates consisted of the hydroxylated forms progoitrin and gluconapoleiferin, while very little of the indole glucosinolate glucobrassicin was modified by hydroxylation or methylation. Biosynthesis of the phenyl glucosinolate nasturtiin was associated with the development of the radicle of the embryoids and the roots of the plantlets. The in vitro glucosinolate synthesis did not yield a glucosinolate profile corresponding to that of the seeds harvested from greenhouse grown plants. However, in vitro plantlets derived from embryoids of high glucosinolate B. napus genotypes produced relatively more alkenyl glucosinolates compared to in vitro plantlets of low glucosinolate genotypes. In breeding programmes in which the double haploid technique is applied, this could be useful to select for genotypes with a low GSL content at an early stage during in vitro culture.

Tropical forests are a major sink for carbon dioxide produced globally. Estimation of above-groundbiomass of these forests is an essential aspect of studies of carbon stocks and the effects of carbon sequestration on the global carbon balance. Long term monitoring plots across several tropical dryevergreen forests in India, in the recent past, shows they are highly carbon dense ranging from 73.06Mg ha-1 to 173.1 Mg ha1. In Sri Lankan forests, biomass estimates are confined to the wet zone forestsand plantations.To assess the carbon dynamics in Sri Lankan dry zone forests, as a pilot study, above-ground biomass infive dry zone forests were estimated using past forest inventory data from 1961. Our objective was todevelop an above-ground carbon database for dry zone forests, which can be used to determine the carbon dynamics in those forests. The data of published stand and stock tables from the five dry zoneforests, Hurulu, Kumbukkan, Kantalai, Pallekelle and Madhu, were converted to above ground biomassusing published allometric models. Estimated above-ground biomass ranged from a minimum of 75.7Mg ha-1 in the Kumbukkan forest to a maximum of 129.6 Mg ha-1 in the Kantalai forest. The total abovegroundcarbon stocks ranged from 37.8 Mg ha-1 in the Kumbukkan forest to a maximum of 64.8 Mg ha-1 inthe Kantalai forest. The average above-ground biomass for dry zone forests was 92.62 Mg ha-1. Whencompared with the wet zone estimates (eg.Sinharaja 336.8 Mg ha-1) the dry zone forests have lowerabove-ground biomass due to high disturbances, low tree density and other factors such as slow growthpattern of most of the tree species. However, present above-ground biomass estimates are not availablefor dry zone forests and estimates from this study can be considered as the above-ground carbon stock1960’s. These estimates shall be presented to assess the carbon dynamics in dry zone forests of SriLanka.

Summary Efforts to improve the induction of embryogenesis in microspore culture of B. napus have focussed to date on growth conditions of the donor plants and culture conditions of the microspores. For initiating haploid development, the first pollen mitosis proceeds in a symmetrical fashion in contrast to the asymmetrical division in normal gametogenesis. Earlier studies have shown that disruption of this asymmetrical division by adding colchicine into the culture medium (25 mgL-1 for 12 h) of microspores increased the number of regenerated embryoids. In the present experiments the effect of higher concentrations and longer colchicine treatments have been analyzed in B. napus. Of the 57 microspore culture experiments with four different genotypes, 69% of the experiments produced a positive effect on embryogenesis. The best results were obtained with the treatment of 100 mgL-1 colchicine for 24 h. This produced a 3 fold increase in the average number of regenerated embryoids. The second best result was obtained with the 10 mgL-1 treatment for 3 days, leading to a 1.8 fold increase in regeneration. The individual treatments showed a strong tendency for the 24- h and 72-h duration of treatments to be significantly better than their controls, while the 6-h treatment resulted in a low level of significance. Colchicine concentrations as low as as 10 mgL-1 were sufficient to improve embryogenesis and the results suggest that treatment durations longer than 24h (or even 72h) may positively affect embryogenesis. A negative effect of colchicine on the regeneration rate was observed in 10% of the experiments, indicating that the developmental stage of microspores at the time of colchicine treatment might be important. During the culture of microspores and the regeneration of embryoids no signs of toxicity, e.g. malformations of embryoids, were observed. The experiments confirm that disruption of cytoskeleton components at or before the first pollen mitosis in vitro contributes to an improved embryogenesis in B. napus.

The effect of colchicine on isolated microspore cultures of Brassica napus was evaluated in order to combine a positive effect of colchicine on the induction of embryogenesis with the possibility to induce chromosome doubling at an early developmental stage, thus avoiding the production of haploid or chimeric plants. Colchicine was added to the culture medium immediately after isolation of B. napus microspores. The cultures were incubated from 6 to 72 h with various concentrations of colchicine. Samples were taken from the regenerating embryoids after 6 weeks for ploidy determination by flow-cytometry.

This study was conducted to understand the role of bacterial–fungal interactions on heavy metal uptake by Zea mays plants. A pot experiment was conducted for 90 days with Z. mays in serpentine soil inoculated with a Gram-negative bacterium, fungus (Aspergilllus sp.) and both microbes to determine the effects of inoculation on nickel, manganese, chromium and cobalt concentrations in plant tissue and soil. Soil nutrients and soil enzyme activities were measured to determine the effect of inoculations on soil quality. Inoculation of microorganisms increased shoot and root biomass, and the maximum biomass was in the bacterial–fungal inoculation. This could be due to the solubilisation of phosphate and production of indole acetic acid. Although the combination treatment contributed to an increase in heavy metal uptake in Z. mays plants, the lowest translocation was observed in the combination treatment. Moreover, the soil available nitrogen, available phosphorous and total organic carbon content were increased with the microbial inoculation. Similarly, the soil dehydrogenase activity was higher as a result of microbial inoculation, whereas the highest dehydrogenase activity was reported in the combination inoculation. This study confirms the synergistic effect of bacterial–fungal inoculation as a soil-quality enhancer and as a plant-growth promoter in the presence of heavy metals.

In angiosperms, archesporial cells in the anther primordium undergo meiosis to form haploid pollen, the sole occupants of anther sacs. Anther sacs are held together by a matrix of parenchyma cells, the connective tissue. Cells of the connective tissue are not known to differentiate. We report the differentiation of parenchyma cells in the connective tissue of two Gordonia species into pollen-like structures (described as pseudopollen), which migrate into the anther sacs before dehiscence. Pollen and pseudopollen were distinguishable by morphology and staining. Pollen were tricolpate to spherical while pseudopollen were less rigid and transparent with a ribbed surface. Both types were different in size, shape, staining and surface architecture. The ratio of the number of pseudopollen to pollen was 1:3. During ontogeny in the connective tissue, neither cell division nor tetrad formation was observed and hence pseudopollen were presumed to be diploid. Only normal pollen germinated on a germination medium. Fixed preparations in time seemed to indicate that pseudopollen migrate from the connective tissue into the anther sac.

Serpentine soils are derived from the weathering of serpentine and ultramafic rocks, which have a high content of ferromagnesian minerals. The high content of heavy metals in serpentine soils alter their physical and chemical properties making them unsuitable for plant growth. There are six serpentine sites in Sri Lanka and the Ussangoda site is on the southern coast in Hambantota. The moisture content, organic matter and cation exchange capacity (CEC) are low in serpentine soils. The available calcium (Ca) content is low and the magnesium (Mg) content is relatively high. The Ca to Mg ratio is 0.60, which is typical for serpentine soils. Two distinct forms of vegetation grow on the Ussangoda serpentine soil. The large plain is covered by stunted, prostrate species with an extensive root system. Patches of shrubs and trees occur on the plains as small islands. The serpentine flora is sharply demarcated from the surrounding non-serpentine flora by their growth habit. The number of plant families and species is lower in the serpentine soil than in the adjacent non-serpentine areas. Four families comprising six species grew only on the serpentine soil. Five species growing in the serpentine soil contained 560 – 830 ppm of nickel (Ni) in their tissues. Hybanthus enneaspermus had 1800 ppm of nickel. Two species, Vernonia zeylanica and Scolopia acuminata, are endemic to Sri Lanka. Keywords: Biodiversity, Evolvulus alsinoides , heavy metals, Hybanthus enneaspermus , serpentine, Ussangoda. DOI: http://dx.doi.org/10.4038/jnsfsr.v39i4.3884 J.Natn.Sci.Foundation Sri Lanka 2011 39 (4): 355 - 363

Mustard (Brassica juncea) accessions from Sri Lanka have a fatty acid profile (FAP) dominated by the undesired erucic acid. Therefore, it is necessary to develop B. juncea lines with canola-quality FAP, carrying reduced erucic acid (50%). To improve the FAP, B. juncea accessions were hybridised with spring-type canola (B. napus) varieties grown in Australia. Interspecific crosses between three B. napus cultivars (♂) and B. juncea accessions (♀) gave crossability of 50–65%. Embryo culturing on Lichter medium overcame post-germination barriers to obtain F1 plants. Culturing of ovules 21 days after pollination was successful and embryos were independent of hormones in the culture medium and directly developed into plants. Seeds of interspecific hybrids had a FAP different from parental values, particularly for oleic and erucic acids. The low oleic acid (13%) in B. juncea increased to 23–26% in hybrids and high erucic acid in B. juncea (41%) declined to 21–23% in hybrids. Linoleic and linolenic acids showed little variation from parental values. FAP of F1 hybrids shifted towards that of canola quality. The F2 seeds had zero erucic acid and high oleic acid similar to or exceeding the canola parent. Successful interspecific hybridisation of B. juncea and B. napus was confirmed by altered FAP and molecular markers. Embryo rescue in interspecific hybrids of B. juncea and B. napus is a simple, powerful biotechnological tool to increase genetic diversity and transcend species barriers to transfer desired genes, between the species. By implementing a crossing strategy, there is a potential to improve the FAP of Sri Lankan mustard towards the canola type.

Consistent callus induction and regeneration of material cultured in vitro is a pre-requisite for somatic cell genetic improvement of plants, through methods such as genetic engineering. This study aims to induce rapid in vitro callusing and regeneration on three local rice varieties by exposure to different culture media. When mature embryos were exposed to three levels of 2,4dichlorophenoxyacetic acid (2,4-D) and one level of thidiazuron (TDZ) (with a short hormone free period in between), all varieties showed rapid regeneration in the absence of a visible callus phase. When the seeds were cultured in 2,4-D for three weeks, at a decreasing concentration of 2,4-D every 7 days, and subsequently treated with TDZ, non-embryogenic calli were obtained that failed to regenerate on hormone free medium. When exposed to 2,4-D for 5 days and subculturcd in hormone free medium for two weeks, embryogenic calli and greening were observed within that period. The concentration and period of exposure to 2,4-D are critical factors for callus induction and regeneration in the genotypes tested.