Using Leaf Bronzing Score to Assess Iron Toxicity Tolerance in Lowland Rice

Iron toxicity is recognized as one of the most widespread soil constraints for rice production, particularly in the Low Country Wet Zone (LCWZ) of Sri Lanka. Underwater logged conditions, soluble iron present in the soil solution is absorbed by paddy roots and is accumulated in the leaves, resulting in poor plant growth, lowering of tillers and severe yield reductions. These characteristics are often accompanied by apparent leaf discoloration or bronzing. The aim of this study was to assess the use of the Leaf Bronzing Score (LBS) to assess its suitability as an indicator of Fe toxicity tolerance/susceptibility. The suitability of LBS of the rice varieties were monitored against the grain yields of each tested variety. This simple and practical approach will result in identifying promising rice varieties that could be used in breeding programs aimed at improving iron toxicity tolerance. The experiment was carried out in the Maha seasons of 2017/2018, at the research field of the Regional Rice Research and Development Center (RRRDC), Bombuwala, located in the LCWZ. The selected location consisted of sandy loam which had a relatively high level of total Fe (589.0±16.51 ppm) and acidity (pH:4.47±0.20). Three rice varieties of unknown iron tolerance, and a further two varieties of known tolerance/susceptible traits, were used as test entries. Varieties were arranged in the field in a Randomised Complete Block Design (RCBD), with three replicates. The Leaf Bronzing Scores (LBS) were determined at different stages of growth while the grain yields were determined at maturity. Observations revealed that there were significant differences in the LBS values between the tested varieties across the different stages of growth. The varieties Kahata Wee and Bw267-3 were the most tolerant as indicated by the lowest LBS value (LBS-1), followed by Bw372 and Bw360. The highest LBS value was recorded in Bw272-6b (LBS-7), indicating its susceptible nature. The grain yield of the five varieties also differed significantly (one-way Anova: F=18843.034, p<0.05). Three rice varieties (Kahata Wee, Bw372, Bw360) consistently recorded higher yields than the other two. The highest grain yield (9.9145 t/ha) was recorded in Kahata Wee, followed by Bw372 (5.1086 t/ha) and Bw360 (4.0462 t/ha). The lowest grain yield of 1.9968 t/ha was recorded in Bw267-3. The trends further showed that the LBS values were negatively correlated with grain yield (Regression Analysis: R2=14%, F=2.112, p<0.05). This observation indicates that the Leaf Bronzing Score could be used as a simple trait to detect iron toxicity tolerance in rice varieties.Keywords: Iron toxicity, Leaf bronzing score, Grain yield, Low country wet zon

Computational modelling of cook-stoves

Combustion inside a cooking stove is complicated to understand and describe. The process is highly dependant on the inlet conditions, fuel used and the geometry of the stove. It is very difficult to predict the distributions of temperature, velocity and product concentrations within the stove. The variation of stove efficiency with respect to boundary conditions is also unknown. The shortcomings have resulted in two major issues; namely, low overall stove efficiency and high emission levels. Computational modelling of the flow field and chemical reactions is a viable method to understand the combustion process in a cooking stove

Learners' Satisfaction, Learning Style Preferences and Effective Use of an OLE

This paper presents the results of an empirical study conducted with a set of students using an online learning environment (OLE) to follow a distance education program. The aim of the study was to find whether students could perform well in examinations using only the Learning Management System (LMS), whether they could use it in an efficient way and whether there was a relationship between studentsâ?? learning styles, number of LMS hits and learning achievements. The students were given access to a specially designed course section. The studentsâ?? learning achievements were evaluated in two tests at different intervals. The study data were gathered using questionnaires and LMS statistics. We found that once the students got acquainted with the environment they could use the LMS more efficiently and managed to get high scores by only using the LMS. Results associated with the learning style preferences imply that we have designed the learning content and the environment to satisfy and support the learners with different learning style preferences

Learners' Satisfaction, Learning Style Preferences and Effective Use of an OLE

This paper presents the results of an empirical study conducted with a set of students using an online learning environment (OLE) to follow a distance education program. The aim of the study was to find whether students could perform well in examinations using only the Learning Management System (LMS), whether they could use it in an efficient way and whether there was a relationship between students’ learning styles, number of LMS hits and learning achievements. The students were given access to a specially designed course section. The students’ learning achievements were evaluated in two tests at different intervals. The study data were gathered using questionnaires and LMS statistics. We found that once the students got acquainted with the environment they could use the LMS more efficiently and managed to get high scores by only using the LMS. Results associated with the learning style preferences imply that we have designed the learning content and the environment to satisfy and support the learners with different learning style preferences

Is risk factor-based screening good enough to detect gestational diabetes mellitus in high-risk pregnant women? A Sri Lankan experience

Background: There is a long lasting dilemma over the ideal screening and diagnostic method in gestational diabetes mellitus (GDM). Even though universal screening is commonly practiced, selective screening based on risk factors is also practiced in some center. The aim of this study is to evaluate the most appropriate method to screen GDM in high-risk pregnant women in Sri Lanka. Methods: This study was a clinic-based, cross-sectional study conducted in a tertiary referral center, Sri Lanka. All women underwent 75 g oral glucose tolerance test at 24-28 weeks of gestation. Diagnosis of GDM was made according to the International Association of the Diabetes and Pregnancy Study Groups (IADPSG) and World Health Organization (WHO) criteria. Results: With universal screening using IADPSG criteria, 23.2% (105/452) were found to have GDM and with risk factor-based screening 20.1% (91/452) were detected to have GDM. The prevalence of GDM dropped to 18.1% when GDM was diagnosed using the WHO criteria with universal screening approach. It was further dropped to 15.7% when the WHO criteria were used along with risk factors-based screening approach. Conclusions: The IADPSG criteria labeled considerably higher number of women as having GDM compared to the WHO criteria. With regards to the screening methods, the risk-based screening had a lower detection rate of GDM; however, it reduced the necessity of screening of women by around 20%

Evaluating the nitrification inhibition potential of selected botanicals and their non-target effects

Nitrification inhibitors (NI) are aimed at improving N-fertilizer use efficiency in cropping systems. This study aimed to assess the nitrification inhibition potential and non-target effects of dry leaf powders (botanicals) of ten plant species [neem (Azadirachta indica), lantana (Lantana camara), karanda (Pongamia pinnata), Brachiaria humidicola, cinnamon (Cinnamomum verum), clove (Syzygium aromaticum), wild-sunflower (Tithonia diversifolia), mee (‎Madhuca longifolia), nutmeg (Myristica fragrans) and pepper (Piper nigram)]. The effect of botanicals on the growth of three ammonia oxidizing bacteria isolates (M4, M5 and M7) and NO3The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Kinetics of oxalate degradation in aerated packed-bed biofilm reactors under nitrogen supplemented and deficient conditions

© 2018 Elsevier Ltd Destruction of oxalate from alumina-refining process liquor is considered essential for many alumina refineries around the world. Some refineries have embraced the use of aerobic bioreactors as a cost-effective destruction method. These processes are often supplemented with an external nitrogen (N) source to facilitate microbial activity, even though such augmentations are undesirable due to increase of operational costs. Until now, there has also only been little information on oxalate degradation kinetics, although this knowledge is essential to design bioreactor processes. Hence, this study aimed at determining oxalate degradation kinetics in two aerobic packed bed biofilm reactors under both N–supplemented and N-deficient conditions. Michaelis-Menten equation was used to derive kinetic parameters for specific oxalate degradation. The N-deficient culture had a higher affinity (Km of 458.4 vs. 541.9 mg/L) towards oxalate and a higher maximum specific oxalate removal rate (Vmax of 161.3 vs. 133.3 mg/(h·g biomass)) compared to the N-supplemented culture, suggesting that the N-deficient culture is better suited to remove oxalate. Microbial community analysis also showed differences in the composition of the two cultures. Based on the kinetic parameters derived, a novel two step oxalate removal process was proposed that capitalises on higher specific oxalate removal rates for efficient oxalate destruction from waste streams of alumina industry

Influences of pH and organic carbon on oxalate removal by alkaliphilic biofilms acclimatized to nitrogen-deficient and supplemented conditions

Accumulation of organic impurities (specifically oxalate) in Bayer liquor is a significant problem for alumina refineries. Microbial degradation is a low-cost solution to the problem, but hostile conditions of Bayer liquor (pH > 14 and nitrogen (N) deficiency) makes it challenging. The solution remains with selection of an appropriate haloalkaliphilic culture and alumina refineries currently have access to two types of bacterial cultures (N-supplemented and N-deficient cultures). To date there is no comparative assessment of the two cultures to examine which one is more suitable to reduce operational risks (i.e. with higher removal efficiencies over a broader range of pH) and costs. Hence, this study compared oxalate removal efficiencies of two packed bed biofilm reactors (N-supplemented and N-deficient) on exposure to a range of influent pH and simple organic compounds. Both reactors were operated (>265 days) at pH 9 and pH influence was compared in batch experiments. Results suggested that both biofilms could tolerate a broad pH range (7–10). The optimal specific oxalate removal rate of N-supplemented reactor was restricted to pH 9, whereas the maximal rate was maintained over a wider pH range (7–8) in N-deficient reactor. In this range, the N-deficient system outperformed the N-supplemented system (105 vs. 130 mg-oxalate/h.g-biomass). Although acclimatised primarily with oxalate, both biofilms simultaneously oxidised other organics (acetate, formate, malonate and succinate) without a noticeable influence on oxalate removal. This study suggests that N-deficient systems are more versatile and better suited to remove organic impurities in Bayer liquor

Rapid start-up of a bioelectrochemical system under alkaline and saline conditions for efficient oxalate removal

This study examined a new approach for starting up a bioelectrochemical system (BES) for oxalate removal from an alkaline (pH > 12) and saline (NaCl 25 g/L) liquor. An oxalotrophic biofilm pre-grown aerobically onto granular graphite carriers was used directly as both the microbial inoculum and the BES anode. At anode potential of +200 mV (Ag/AgCl) the biofilm readily switched from using oxygen to graphite as sole electron acceptor for oxalate oxidation. BES performance was characterised at various hydraulic retention times (HRTs, 3–24 h), anode potentials (-600 to +200 mV vs. Ag/AgCl) and influent oxalate (25 mM) to acetate (0–30 mM) ratios. Maximum current density recorded was 363 A/m 3 at 3 h HRT with a high coulombic efficiency (CE) of 70%. The biofilm could concurrently degrade acetate and oxalate (CE 80%) without apparent preference towards acetate. Pyro-sequencing analysis revealed that known oxalate degraders Oxalobacteraceae became abundant signifying their role in this novel bioprocess