Influence of environmental variations on physiological attributes of sunflower

High degree of adaptability, wide range of climatic conditions, high photosynthetic capacity, maximum stomatal conductance and efficient hydraulic mechanism allow sunflower crop to be productive in broad range of environments. Combined effects of environmental factors not only modify plant phenology but also cause many physiological changes. Field experiments, one each in spring and autumn were conducted at Pir Mehr Ali Shah, Arid Agriculture University Rawalpindi, Pakistan for 2 years (2007 and 2008) to document the effect of environmental variations on the physiological functions of sunflower hybrids. Four sunflower hybrids, Alisson-RM, Parasio-24, MG-2 and S-278 were planted in randomized complete block design with 4 replications. The data on physiological attributes like photosynthetic rate, stomatal conductance and transpiration rate at 10 days interval after complete emergence to 60 days after emergence (DAE) was recorded. Overall higher values of photosynthetic rate, stomatal conductance and transpiration rate were recorded during spring as compared to autumn for both the years. Photosynthates accumulation and utilization was depressed in cold imposing a restriction on biomass production than at warm temperature. Physiological performance of all the hybrids during spring at the start was slower as compared to autumn. Progressive increase in photosynthetic rate, stomatal conductance and transpiration was recorded with the gradual increase in temperature up to a certain level during spring but further increase in temperature caused decline in these attributes. However during autumn, values of all these 3 physiological attributes were higher at the start those declined with gradual decrease in temperature later in the season

Growth rhythms in sunflower (Helianthus annuus L.) in response to environmental disparity

Sunflower hybrids maintain high level of stability in a variety of environments. Environmental variations affect and modify plant attributes like growth, development and assimilation through physio-morphicfunctions, thus modifying plant phenology. Field experiments, one each in spring and autumn, were conducted at Pir Mehr Ali Shah, Arid Agriculture University, Rawalpindi, Pakistan for two years (2007 and 2008) to document the effect of environmental variations on growth rhythms of sunflower hybrids. Four Sunflower hybrids, Alisson-RM, Parasio-24, MG-2 and S-278 were planted in randomized complete block design with four replications. The data based on physiological attributes like leaf area (LA),specific leaf area (SLA), crop growth rate (CGR) and net assimilation rate (NAR) at 10 days interval after complete emergence to 60 days after emergence (DAE) were recorded. Overall higher values of LA, SLA, CGR and NAR were recorded during spring as compared to autumn for both years. LA, CGR and NAR of all the hybrids followed a sigmoid curve pattern during both seasons; however, at the start of the season lesser values were observed during spring as compared to autumn. SLA exhibited anopposite trend and continuously decreased till the end. Sigmoid curve pattern of LA, CGR and NAR may be related to environmental variables like temperature and sunshine hours. The decrease after a peak may be due to senescence of older leaves and shifting of crop from vegetative to reproductive phase

Evaluation of combined disc method for the detection of metallo-β-lactamase producing Gram negative bacilli

Aims: Infections due to metallo-β-lactamase (MBL) producing Gram negative rods are a cause of high mortality and morbidity. Early detection by an economical and accurate method may improve patient outcome. This study was aimed to evaluate the diagnostic accuracy of combined disc method for MBL detection by comparing it with MBL-Etest.Methodology and Results: This cross-sectional, validation study was carried out in the Department of Microbiology, Army Medical College, National University of Sciences and Technology, Rawalpindi, over a period of six months. A total of 52 non-duplicate Gram-negative rods isolated from the routine clinical specimens and found resistant to meropenem/imipenem on Kirby Bauer Disc Diffusion method were subjected to two tests for metallo-β-lactamase detection. One was combined Disc test using imipenem with Ethylene Diamine Tetraacetic Acid (EDTA), where a strain showing an increase in zone of inhibition of combined disc of ≥ 7 mm as compared to imipenem alone, was considered as MBL producer and the other one was MBL-Etest for which results were interpreted as per manufacturer’s guidelines. Combined disc method for MBL detection was found to have a sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 97.5%, 100%, 100%, 92% and 98%.Conclusion, Significance and Impact of study: Combined disc method is an economical and reliable method for metallo-β-lactamase detection which can be used routinely in any laboratory

Detection and Antibiotic Susceptibility Pattern of Biofilm Producing Gram Positive and Gram Negative Bacteria Isolated From a Tertiary Care Hospital of Pakistan

Microorganisms adhere to non-living material or living tissue, and form biofilms made up of extracellular polymers/slime. Biofilm-associated microorganisms behave differently from free-floating bacteria with respect to growth rates and ability to resist antimicrobial treatments and therefore pose a public health problem. The objective of this study is to detect the prevalence of biofilm producers among Gram positive and Gram negative bacteria isolated from clinical specimens, and to study their antimicrobial susceptibility pattern. The study was carried out from October 2009 to March 2010, at the Department of Microbiology, Army Medical College/ National University of Sciences and Technology (NUST), Rawalpindi, Pakistan. Clinical specimens were received from various wards of a tertiary care hospital. These were dealt by standard microbiological procedures. Gram positive and Gram negative bacteria isolated were subjected to biofilm detection by congo red agar method (CRA). Antimicrobial susceptibility testing of those isolates, which showed positive results (slime production), was done according to the Kirby-Bauer disc diffusion technique. A total of 150 isolates were tested for the production of biofilm/slime. Among them, 81 isolates showed positive results. From these 81, 51 were Gram positive and 30 were Gram negative. All the 81(54%) slime producers showed reduced susceptibility to majority of antibiotics. Bacterial biofilms are an important virulence factor associated with chronic nosocomial infection. Detection of biofilm forming organisms can help in appropriate antibiotic choice

Salt stress induces genotype-specific DNA hypomethylation in ZmEXPB2 and ZmXET1 genes in maize

Maize, a moderately salt sensitive crop, first experiences osmotic stress that cause reduction in plant growth under salt stress. Fluctuation in cell wall elongation is one of the reasons of this reduction. Along with others, two important proteins expansins and xyloglucan endotransglucosylase are involved in regulation of cell wall elasticity, but the role of epigenetic mechanisms in regulating the cell wall related genes is still elusive. The present study was conducted with the aim of understanding the role of DNA methylation in regulating ZmEXPB2 and ZmXET1 genes. One salt sensitive and one salt tolerant maize cultivar was grown under hydroponic conditions at different levels of salt stress: T1 = 1 mM (control), T2 = 100 mM and T3 = 200 mM in three replicates. DNA and RNA were extracted from roots. After bisulfite treatment, Methyl Sensitive PCR was used for the DNA methylation analysis. It was revealed that fragment in promoter of ZmEXPB2 gene showed high level of DNA methylation under T1 in both varieties. Comparison of different stress treatments revealed decrease in DNA methylation with the increase in salt stress, significantly lower methylation appearing in T3. Similarly, the fragment in promoter of ZmXET1 gene also showed high levels of DNA methylation in T1. When different treatments were analysed, this gene significantly hypomethylated at T2 which continued to decrease in T3 in sensitive variety but remain stable in tolerant variety. Although, further in-depth analysis is required, our results demonstrate region-specific and genotype-specific methylation shift in the promoter of the ZmEXPB2 and ZmXET1 genes when subjected to the salt stress confirming the epigenetic regulation of these genes under stress conditions