University of Peradeniya

About: University of Peradeniya is a education organization based out in Kandy, Sri Lanka. It is known for research contribution in the topics: Population & Poison control. The organization has 5970 authors who have published 7388 publications receiving 197002 citations.

Spatial distribution of fluoride in groundwater of Sri Lanka

Abstract: Fluoride ions in drinking water is well known for both beneficial and detrimental effects on health. Millions of inhabitants in the Dry Zone of Sri Lanka are vulnerable to fluorosis due to consumption of high fluoride groundwater. The objective of this study is to upgrade the spatial distribution map of groundwater fluoride levels in Sri Lanka. The map was prepared using nearly 14000 groundwater fluoride data that were collected from primary and secondary sources. The fluoride map of Sri Lanka indicates that the climate and hydrological conditions appear to play a major role in the geochemical distribution of fluoride in groundwater. In some cases, over 25 % of wells have more than 2 mg/L of fluoride, which is much higher than the recommended level for tropical countries. As shown in the map, even within the Dry Zone region, some low fluoride regions can be observed. This may probably be due to the effect of surface water, which contains fairly low levels of fluoride. In general, from among the chemical parameters in groundwater, fluoride stands out as an ion that appears to seriously affect the water quality of the Dry Zone. Doi: http://dx.doi.org/10.4038/jnsfsr.v40i4.5044 J.Natn.Sci.Foundation Sri Lanka 2012 40 (4):303-309

Plasticity of photosynthetic heat tolerance in plants adapted to thermally contrasting biomes.

Abstract: In many biomes, plants are subject to heatwaves, potentially causing irreversible damage to the photosynthetic apparatus. Field surveys have documented global, temperature-dependent patterns in photosynthetic heat tolerance (PHT ); however, it remains unclear if these patterns reflect acclimation in PHT or inherent differences among species adapted to contrasting habitats. To address these unknowns, we quantified seasonal variations in Tcrit (high temperature where minimal chlorophyll-a fluorescence rises rapidly, reflecting disruption to photosystem II) in 62 species native to 6 sites from 5 thermally contrasting biomes across Australia. Tcrit and leaf fatty acid (FA) composition (important for membrane stability) were quantified in three temperature-controlled glasshouses in 20 of those species. Tcrit was greatest at hot field sites and acclimated seasonally (summer > winter, increasing on average 0.34 °C per °C increase in growth temperature). The glasshouse study showed that Tcrit was inherently higher in species from warmer habitats (increasing 0.16 °C per °C increase in origin annual mean maximum temperature) and acclimated to increasing growth temperature (0.24 °C °C-1 ). Variations in Tcrit were positively correlated with the relative abundance of saturated FAs, with FAs accounting for 40% of Tcrit variation. These results highlight the importance of both plastic adjustments and inherent differences determining contemporary continent-wide patterns in PHT .

Soil moisture and potassium affect the performance of symbiotic nitrogen fixation in faba bean and common bean

Abstract: Potassium (K) is reported to improve plant's resistance against environmental stress. A frequently experienced stress for plants in the tropics is water shortage. It is not known if sufficient K supply would help plants to partially overcome the effects of water stress, especially that of symbiotic nitrogen fixation which is often rather low in the tropics when compared to that of temperate regions. Thus, the impact of three levels of fertilizer potassium (0.1, 0.8 and 3.0 mM K) on symbiotic nitrogen fixation was evaluated with two legumes under high (field capacity to 25% depletion) and low (less than 50% of field capacity) water regimes. Plants were grown in single pots in silica sand under controlled conditions with 1.5 mM N (15N enriched NH4NO3). The species were faba bean (Vicia faba L.), a temperate, amide producing legume and common bean (Phaseolus vulgaris L.), a tropical, ureide producing species. In both species, 0.1 mM K was insufficient for nodulation at both moisture regimes, although plant growth was observed. The supply of 0.8 or 3.0 mM K allowed nodulation and subsequent nitrogen fixation which appeared to be adequate for respective plant growth. High potassium supply had a positive effect on nitrogen fixation, on shoot and root growth and on water potential in both water regimes. Where nodulation occurred, variations caused by either K or water supply had no consequences on the percentage of nitrogen derived from the symbiosis. The present data indicate that K can apparently alleviate water shortage to a certain extent. Moreover it is shown that the symbiotic system in both faba bean and common bean is less tolerant to limiting K supply than plants themselves. However, as long as nodulation occurs, N assimilation from the symbiotic source is not selectively affected by K as opposed to N assimilation from fertilizer.