33 research outputs found
Effects of Controlling pH with Hydrochloric Acid on the Growth, Yield, and Fruit Quality of Greenhouse Tomato Grown by Nutrient Film Technique
No full textCROPSIM — WHEAT: A model describing the growth and development of wheat
No full text Crop simulation models consolidate mathematical representations of the various physiological processes underlying crop growth and development into an entity that can be used to predict the outcome of various crop, soil and weather scenarios. For wheat, a number of simulation models are already available, but most of these do not appear to be set-up to facilitate easy comparison of model outputs with experimental data, to allow easy modification for new cultivars, and to facilitate the addition of disease routines, an aspect necessary for models to be useful in the general field situation. Cropsim-wheat was developed to help overcome some of these deficiencies.The model assumes that a crop consists of a collection of uniform plants, and performs calculations on a daily basis. It is driven by daily weather data dealing with solar radiation receipt, maximum and minimum temperatures, and precipitation. Water and nitrogen balance subroutines are included, and the rate of various crop processes is modulated through the use of multipliers that reflect the water and nitrogen states of the crop. Developmental processes are simulated using the concept of "biological days", a time measure that equates to chronological days under optimum conditions. The phases into which the life-cycle is broken relate closely to those in the widely used "Zadoks" scale. Dry matter accumulation is calculated from intercepted radiation, and distributed largely on the basis of demand. A minimum fraction of daily assimilate, however, is reserved for root growth. Leaf area is computed on the basis of potential leaf size and available dry matter, whereas stem and spike areas are calculated from the stem and spike weights. Both leaf and stem area are used in calculating radiation interception. Critical stresses, water saturation during early seedling growth and low temperature during the winter period, can result in plant death. Low temperatures, when they occur around heading, can also result in sterility and reduced grain number.The model performance has been compared with datasets from North America and Europe, and results of these comparisons will be conveyed in companion publications. The model has been set-up, however, on the premise that model development should be a continuing process as new datasets become available and new applications are contemplated. With this in mind, it has been built to use file structures that facilitate the handling and storage of field data, and the easy comparison of field and simulated data. It should thus be useable by experimenters as a tool to help in the analysis of field studies. Key words: Wheat, simulation, nitrogen, water, development, growth </jats:p
Wheat Spike Temperature in Relation to Base Temperature for Grain Filling Duration
No full text Estimates of the base temperature for grain filling duration of wheat (Triticum aestivum L.) differ between outdoor and indoor studies. This study was set up to determine whether this difference could be attributed to variation in spike-air temperature differentials. Spike and/or spikelet temperatures were determined in wheat grown outdoors as well as indoors. Spike temperature, measured with an infrared thermometer, of wheat grown outdoors with adequate water supply was 1.5 °C greater than air temperature while spikelet temperature measured with a thermocouple closely approximated air temperature. In indoor grown wheat, on the other hand, regardless of the magnitude of air temperature, spikelet temperature was found to be 3–4 °C above that of air when lights were on. Estimating the base temperature for grain filling duration with data from a previous indoor study, with compensation for the 3–4 °C increase in spikelet temperature, resulted in 8.8 °C base temperature for grain filling duration, comparable to that obtained in outdoor studies. Differences between outdoor and indoor studies may thus reflect spike-air temperature differentials. Estimation of the base temperature for grain filling with air temperature appears appropriate for outdoor studies. Key words: Triticum aestivum (L.), base temperature, grain filling duration, wheat </jats:p
Postanthesis biomass accumulation and respiration in shaded and unshaded wheat (<i>Triticum aestivum</i> L.)
No full text Respiration significantly influences the carbon balance of a crop. In wheat (Triticum aestivum L.), biomass equivalent to between 40 and 75% final grain mass can be lost through shoot respiration during grain fill. This study examines the relationship between changes in biomass and respiration of the aboveground plant parts of shaded and unshaded wheat during grain fill. Two spring wheat cultivars, Max and Katepwa, were grown indoors with and without shade, and various biomass components and aboveground CO2 efflux rates were determined from anthesis to maturity. Maximum leaf biomass in Max was attained prior to anthesis while in unshaded Katepwa plants leaf biomass increased up to 35 d after anthesis. The stem changed from functioning as a source and became a sink 28 and 35 d after anthesis in the control plants of Max and Katepwa, respectively. The effect of shading on spike growth became apparent two weeks after anthesis. The CO2 efflux rate for unshaded Max and Katepwa plants declined significantly from 279 to 122 and from 210 to 141 mg CO2 plant−1 d−1, respectively, from anthesis through to maturity. Imposition of shade resulted in significantly lower CO2 efflux rates compared to the unshaded plants. Shade, however, exerted no influence on the estimated maintenance respiration coefficient (m) of a two component respiration model, although this coefficient declined 88% in Max throughout grain fill and declined up to 14 d after anthesis and remained stable thereafter in Katepwa. It was concluded, therefore, that shading affects total respiration through its impact on growth, but exerts no direct effect on the basic pattern of change in maintenance respiration during grainfill. Key words: Biomass accumulation, respiration rate, maintenance respiration coefficient, Triticum aestivum L. </jats:p
Effects of photoperiod on leaf appearance rate and leaf dimensions in winter and spring wheats
No full text Research on genotypic variation in the response of leaf-area production and expansion to photoperiod in wheat is limited. Growth-cabinet experiments using four spring and four winter wheat (Triticum aestivum L.) cultivars and four photoperiod (8, 12, 16 and 20 h) treatments were thus conducted with the objective of investigating the effect of photoperiod on leaf appearance rate and leaf dimensions. Winter wheats were grown without vernalization. In the spring wheats, flag leaves and spikes were formed under the longer photoperiod (16 and 20 h) treatments, and leaf number increased linearly with time. At the shorter photoperiods, flag leaves and spikes appeared in some cultivars only, and the rate of increase in leaf number decreased in the later stages. Final leaf number was greater at shorter photoperiods. In the winter cultivars, more leaves appeared than in the spring types under the longer photoperiods. For leaves 3–7, leaf number was a linear function of time, with photoperiod and cultivar effects. For one of four spring cultivars, the rate of leaf appearance was greater at 8 h than at 20 h, whereas for three of the winter cultivars the reverse was true. Leaf length increased with leaf number up to at least nodes 5–6 for both spring and winter types but decreased for the later-formed leaves for the spring but not for the winter types. Leaves of plants grown under photoperiods longer than 8 h were longer and broader than those grown under the short photoperiod, and the effect was more pronounced in winter than in spring cultivars. Such genotypic differences in the direct effects of photoperiod on leaf dimensions, which could influence the rates of leaf-area production and dry-matter accumulation under field conditions, emphasize that future studies should incorporate genotypes from different eco-physiological regions and that simulation models of wheat growth and development may need to account for variability in the control of vegetative growth. Key words: Wheat, photoperiod, leaf appearance rate, leaf length, leaf width </jats:p
Effects of planting date on the development and yield of spring wheat: Simulation of field data
No full text Much of the work on planting-date effects has been carried out with old cultivars and over a relatively few years. This study was conducted to use data from a recent study to determine whether a simulation model (Cropsim-wheat) could be used to examine the response of modern cultivars to planting date over an extended run of years. Field data for four spring wheat (Triticum aestivum L.) cultivars seeded at 12 planting dates, ranging from 29 April to 12 June, at 4-d intervals at Crookston, Minnesota, in 1992 were used. For all genotypes, crop duration was shortened as planting was delayed from 29 April to 23 May. Further delay in planting lengthened this duration. Simulation outputs for developmental aspects closely matched the field data. The early plantings yielded less than those established somewhat later, with the highest grain yields resulting from mid-May plantings. Cultivar Marshall planted on 7 May produced the highest yield (5.5 t ha−1) of any cultivar. Late plantings decreased grain yield. Grain number appeared to be the major component affecting grain yield. Simulation outputs from the basic model, which computed grain number as a function of biomass shortly after anthesis, did not match well the field data for early and late plantings. The inclusion of functions that related grain number to solar radiation and maximum temperature around anthesis and to biomass improved the predictions for plantings early and later in the season. The inclusion of these functions in wheat simulation models may be necessary for application to situations that result in differences in environmental conditions around anthesis. Key words: Wheat, planting date, simulation, yield, grain number </jats:p
Comparison of intravenous versus perineural dexamethasone as a local anaesthetic adjunct for peripheral nerve blocks in the lower limb: A meta-analysis and systematic review.
No full textAs a local anaesthetic adjunct, the systemic absorption of perineural dexamethasone in the lower limb could be restricted because of decreased vascularity when compared with the upper limb.
To compare the pharmacodynamic characteristics of intravenous and perineural dexamethasone in the lower limb.
Systematic review of randomised controlled trials with meta-analysis.
Systematic search of Central, Google Scholar, Ovid Embase and Ovid Medline to 18 July 2023.
Randomised controlled trials, which compared the intravenous with perineural administration of dexamethasone as a local anaesthetic adjunct in peripheral nerve blocks for surgery of the lower limb.
The most common peripheral nerve blocks were femoral, sciatic and ankle block. The local anaesthetic was long acting in all trials and the dose of dexamethasone was 8 mg in most trials. The primary outcome, the duration of analgesia, was investigated by all nine trials ( n = 546 patients). Overall, compared with intravenous dexamethasone, perineural dexamethasone increased the duration of analgesia from 19.54 to 22.27 h, a mean difference [95% confidence interval (CI) of 2.73 (1.07 to 4.38) h; P = 0.001, I2 = 87]. The quality of evidence was moderate owing to serious inconsistency. However, analysis based on the location of the peripheral nerve block, the type of local anaesthetic or the use of perineural adrenaline showed no difference in duration between intravenous and perineural dexamethasone. No differences were shown for any of the secondary outcomes related to efficacy and side effects.
In summary, moderate evidence supports the superiority of perineural dexamethasone over intravenous dexamethasone in prolonging the duration of analgesia. However, this difference is unlikely to be clinically relevant. Consideration of the perineural use of dexamethasone should recognise that this route of administration remains off label
Postanthesis temperature effects on duration and rate of grain filling in some winter and spring wheats
No full text To help define traits that are likely to improve wheat (Triticum aestivum L.) grain yield in a warm, humid continental climate, genotypic variations in various grain growth characteristics in wheat were examined. Winter habit cultivars were grown indoors under a 16-h photoperiod and at day/night temperatures of 20/15 °C, and spring habit cultivars at temperatures ranging from 15/15 °C to 30/25 °C. Grain-filling duration of the winter wheats varied from 36.4 d for Peking-10 to 31.8 d for Priboy. Final kernel weights, which varied from 61.7 mg for Lovrin-10 to 38.3 for Jokionen-3057, were highly correlated with rates of dry matter accumulation. Grain-filling duration of the spring wheats ranged from 56.4 to 47.0 d at 15/15 °C, and from 23.8 to 18.1 d at 30/25 °C. Grain number per spike decreased from 15/15 °C to 30/25 °C. The inverse of grain-filling duration was linearly related to mean temperature, with the intercept on the x-axis (the base temperature of grain filling) being the same for all cultivars. Variation for grain-filling duration among the genotypes tested was present, although small in relation to temperature effects. Breeding for extended grain-filling duration as a strategy for increasing wheat grain yield in a warm climate will thus be difficult. However, an application of the degree-day concept would be desirable. Key words: Triticum aestivum (L.), grain-filling duration, rate of grain filling, temperature </jats:p
A retained foreign body granuloma mimicking a left ventricular psuedoanuerysm
No full textAbstractIntroductionGossypiboma, also referred to as a textiloma, gauzoma or muslinoma describe a mass in the body composed of a central cotton core surrounded by a foreign body reaction. It has an estimated incidence of 1/1000–1/10000 surgeries, occurring in the abdomen (56%), pelvis (18%) and least commonly the thorax (11%) and represents an unfortunate event for both the patient and the operating surgeon with severe liability implications.Presentation of caseWe report a case of a 49-year-old male with Marfan Syndrome who was admitted to the cardiology department with a four day history of shortness of breath and associated dull, non-radiating chest pain. Past history included a previous Bentall procedure for a type-A aortic dissection and coronary artery bypass grafting involving a saphenous vein graft to the right coronary artery.A computed tomography (CT) scan showed a round, heterogeneous mass measuring 14×9cm with lobulated contours, situated adjacent to the left ventricle along the left posterior region of the aorta. The mass was resected and further dissection revealed a plastic band harboured from the core of the mass.DiscussionThe majority of cases of intrathoracic gossypiboma present as intractable cough or an incidental finding on radiological evaluation. Dyspnoea alone is relatively underreported as a presenting symptom of this conditionConclusionThis case highlights the important clinical history features for diagnosing this surgical error, including persistent respiratory symptoms and a history of cardio-thoracic surgery. It also emphasizes on the need for implementing definite strategies to prevent the occurrence of gossypiboma in surgical practice
