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Senadheera P.,The Open University of Sri Lanka | Tirimanne S.,University of Colombo | Maathuis F.J.M.,University of York
Rice Science | Year: 2012

Salinity stress induces oxidative stress caused by reactive oxygen species (ROS): superoxide radicals, hydrogen peroxide (H 2O 2) and hydroxyl radicals. Activities of both enzymatic and non-enzymatic components of the antioxidant system and related growth parameters were studied in the roots of the salt tolerant rice variety FL478 and the sensitive variety IR29 in response to long term stress (12 d) induced by 50 mmol/L NaCl. The comparative study showed that FL478 maintained higher relative growth rate and lower Na +/K + in the roots than IR29 due to a higher membrane stability index that effectively exclude Na +. Lower TBARS (thiobarbituric acid reactive substance) content in FL478 roots indicated that its membrane was relatively unaffected by ROS despite high H 2O 2 content recorded under the salinity stress. Relatively higher superoxide dismutase activity along with a parallel increase in transcript level of superoxide dismutase (Os07g46990) in FL478 indicated that this protein might make a vital contribution to salt stress tolerance. Although the content of ascorbic acid remained unchanged in FL478, the activity of ascorbic peroxidases (APOXs) was reduced comparably in the both varieties. Transcriptomic data showed that a larger number of peroxidase genes were upregulated in FL478 compared to IR29 and several of which might provide engineering targets to improve rice salt tolerance. © 2012 China National Rice Research Institute.

Perera K.A.R.S.,The Open University of Sri Lanka | Amarasinghe M.D.,University of Kelaniya
Atmospheric Environment | Year: 2016

Characterization of the micro-tidal mangrove forests in Negombo estuary, located on the west coast of Sri Lanka, with respect to its capacity to remove atmospheric carbon and sequestration in above and below ground plant components is the objective of this study. These mangroves constitute both natural stands (e.g. Kadolkele) and woodlots planted, protected and managed by fishermen (e.g. Wedikanda) to extract twigs and branches to construct "brush parks", a traditional method of fishing in this estuary. Both types of mangrove stands support high species richness and structural diversity, indicating planted mangrove areas have reached a semi-natural state. Allometric relationships were used to calculate biomass increment. Differences in litterfall, above and below ground biomass increment and net primary productivity (NPP) of the two types of mangrove areas were statistically insignificant, thus indicating that they are structurally and functionally comparable. Average rate of mangrove litterfall in Negombo estuary was 802 ± 25 g m-2y-1. The average above ground biomass increment was 1213 ± 95 gm-2y-1 and below ground increment was 267 ± 18 gm-2y-1, thus the average NPP of these mangroves was 2282 ± 125 g m-2y-1. NPP showed a decreasing trend from water towards land, in line with plant density and leaf area index. A statistically significant relationship was found between vegetation structure (represented by complexity index), NPP and rate of organic carbon accumulation in mangroves. Potential carbon accumulation capacity of mangroves of Negombo estuary was estimated to be approximately 12 t ha-1y-1, which is equivalent to the amount of carbon emitted as CO2 through combustion of 19,357 L of diesel or 22,212 L of gasoline in motor vehicles. Potential atmospheric carbon removal capacity of Negombo estuarine mangroves (350 ha in extent) therefore was estimated to be 4143 t y-1, which is equivalent to removal of CO2 emitted through combustion of 6,779,000 L of diesel or 7,779,000 L of gasoline within a year. © 2016 Elsevier Ltd.

Dias T.,University of Manchester | Delkumburewatte G.B.,The Open University of Sri Lanka
Journal of the Textile Institute | Year: 2010

The absorbency properties of knitted structures are very important in designing garments that both remove liquid sweat from the skin and provide tactile and sensorial comfort to the wearer. Water absorbency by knitted spacer structures was experimentally investigated using a gravimetric absorbency tester to record absorbency rate, total absorbency and time taken to saturate the structure. The geometry of spacer structures was analysed and a model created to define the capillary characteristic in the spacer yarn. Absorbency into the spacer structures was modelled using the fabric parameters, the capillary radius and the properties of water. Experimental and theoretical results were compared to validate the models. © 2010 The Textile Institute.

Senadheera P.,The Open University of Sri Lanka
Methods in molecular biology (Clifton, N.J.) | Year: 2012

Exposure to high ambient levels of NaCl affects plant water relations and creates ionic stress. To a large extent, responses to such stress depend on the action of membrane transporters, particularly those that move cations such as Na(+) and K(+). A genomics approach can greatly help with the identification of important membrane transporter genes. This can be done by comparing transcriptomes of salinized and non-salinized plants, by comparing tolerant and non-tolerant species, or by using intraspecies variation. This chapter describes a protocol using oligo-microarrays to compare salinity treated (50 mM NaCl) and non-treated rice roots, presenting protocols for growth, RNA isolation, cDNA synthesis and labeling, and a summary of data collection, analysis, and interpretation. Although focused on rice root tissue, the described procedures can be applied to many different treatments, tissues, and plant species.

Weerahewa H.L.D.,The Open University of Sri Lanka | Adikaram N.K.B.,University of Peradeniya
Journal of Horticultural Science and Biotechnology | Year: 2011

Internal browning (IB) is a physiological disorder that develops in harvested pineapple (Ananas comosus) 'Mauritius' fruit during prolonged periods of cold storage. A brief exposure of fruit to low temperature (i.e., 4°C for 60 min) prior to cold storage at 10°C reduced the incidence of IB by 40% in both core and flesh tissues.When subjected to 4°C for 60 min before or after a heat-shock (38°C for 60 min), pineapple fruit developed 88% and 40% less IB in the flesh and core areas, respectively, than in control fruit which were not subjected to 4°C for 60 min. Intermittent warming (IW) involving the exposure of pineapple fruit to 28° - 30°C for 8 h every 6 d during 21 d of storage at 10°C and 85% RH, reduced the incidence of IB by ≥ 80% in the core, and by ≥ 50% in flesh tissue. Fruit subjected to IW showed only isolated areas of IB in their flesh tissue, and this was found in only 40% of the total fruit treated. Heat-shock (38°C for 60 min) before or after a low temperature (i.e., 4°C for 60 min) treatment, slowed fruit ripening slightly, but this effect was not observed in fruit subjected to IW. Cell damage was less in fruit tissues showing no symptoms of IB when fruit were given a heat-shock treatment, before or after a low temperature treatment.

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