The relationship between the water relations of six olive cultivars exposed to different soil temperatures (14 ± 0.1, 9.9 ± 0.1 and 5.8 ± 0.2°C) and their inherent frost resistance (as determined by two different methods) was investigated. Soil chilling was achieved by introducing pots of olive plants into water baths. The water relations of these plants were compared to those of plants kept under conditions of room temperature. The cultivars Frantoio, Picual and Changlot Real began to show significant dehydration below 14°C, while Cornicabra, Arbequina and Ascolana Tenera showed this below 10°C. This response is probably due to delayed stomatal closure. Only Cornicabra and Picual showed a significant reduction in leaf conductance (below 10°C and 6°C respectively). This absence of stomatal control led to a significantly greater dehydration in Ascolana Tenera. These variations in response to the soil chilling temperature suggest that different mechanisms may be at work, and indicate that would be necessary to study the influence of rootstock in the frost resistance of olive plants. The variations recorded grouped the cultivars as either resistant (Cornicabra), tolerant (Picual, Ascolana Tenera and Arbequina), or sensitive (Frantoio and Changlot Real). This classification is in line with the frost resistance reported for these cultivars in the literature, and with the results obtained in the present work using the stomatal density and ion leakage methods of determining such resistance.Additional key words: chilling-induced dehydration, frost resistance, leaf conductance, root signal, water potential. ResumenRespuesta de las relaciones hídricas al frío en el suelo de seis variedades de olivo (Olea europaea L.) con diferente resistencia al frío Se ha investigado la relación existente entre el estado hídrico de 6 variedades de olivo expuestas a diferentes temperaturas del suelo y su resistencia al frío (determinada por dos métodos). El frío del suelo fue conseguido introduciendo las macetas de las plantas de olivo en baños de agua. Se comparó el estado hídrico de estas plantas con el de plantas en condiciones de temperatura ambiente. Las variedades Frantoio, Picual y Changlot Real comenzaron a mostrar una deshidratación significativa por debajo de 14°C, mientras que para Cornicabra, Arbequina y Ascolana Tenera lo fue por debajo de 10°C. Esta respuesta es posiblemente debida a un retraso en el cierre estomático. Solamente Cornicabra y Picual mostraron una reducción significativa de la conductancia de la hoja (por debajo de 10°C y 6°C respectivamente). Esta ausencia de control estomático condujo a una significativa mayor deshidratación en Ascolana Ternera. Estas variaciones en respuesta al frío en el suelo sugieren diferentes mecanismos de actuación, e indican que la utilización de un portainjerto puede dar resistencia al frío en plantas de olivo. Los datos agruparon las variedades como resistentes (Cornicabra), tolerantes (Picual, Ascolana Tenera y Arbequina) o sensibles (Frantoio y Changlot Real). Esta clasif...
With the aim at finding a method for the selection of a suitable demulsifier for crude oil dehydration, five crude/associated water/effective demulsifier real systems were evaluated in this study. Likewise, based on the existing knowledge about the fundamentals of emulsion stabilization process, the typical characteristics of each element of the systems, which represent the variables or factors governing the process, were chosen. These variables were: in the crude oil, the acidity number, as a measure of its polarity; in the associated water, the salinity; and in the demulsifier, the relative solubility number (RSN). A hypothesis based on the surfactant affinity difference (SAD) model is proposed. This model was adapted to the specific case of crude oil chemical demulsification. A simplified mathematical expression was obtained, which establishes a relation between the crude oil nature, the associated water salinity, and the demulsifier hydrophilicity. The data obtained from the evaluation of the selected characteristics were introduced into the model. As a result, the following empirical relationship was obtained: where S is the associated water salinity and A is the crude oil acidity number, variables which are easily measured. RSN values were calculated and compared with those obtained from experiments. Except in one case, the calculated RSN value approximates very closely the experimental one. It is therefore concluded that this correlation serves to select the appropriate demulsifier to dehydrate a given crude oil, based on the simple procedure outlined above. Introduction Design and selection of demulsifiers for dehydrating crude oils have been performed using the classical bottle test. This consists of a large number of laboratory essays. The results of these tests should be confirmed, validated and improved by field tests. The empirical approach that forces the execution of a large number of rigorous essays, is a consequence of: the multiple factors involved in the emulsion stabilization/destabilization process, the difference between crude oil emulsions, and the changes that take place in these emulsions during the life of the production well. Besides, the techniques used to investigate the main factors related to demulsifier performance are tedious and complicated. Instead, the use of an empirical procedure, like the bottle test, gives the most practical solution. Because of the increasing knowledge of the factors related to formation/breaking of the crude oil emulsion, demulsifier selection could be carried out in the future on a more scientific base. Background Emulsion stability is governed by different factors that characterize a component or have effects on the system:–Water phase salinity and pH,–Oil organic nature (paraffinic, aromatic or asphaltenic), - Relative water/oil surfactant affinity,–Oil/water ratio,–Oil and water viscosity and density difference,–Temperature. At the same time, the affinity or relative solubility of the surfactant in the oil or the water phase depends on the salinity of the water phase, the oil nature, and the temperature. Therefore, in a water/oil/surfactant system, if the surfactant affinity to the oil phase is greater than to the water phase, the system forms an water-in-oil emulsion. P. 601^
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