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Fernandez I.,University of Almeria | Acien F.G.,University of Almeria | Fernandez J.M.,University of Almeria | Guzman J.L.,University of Almeria | And 2 more authors.
Bioresource Technology | Year: 2012

A dynamic model for microalgal culture is presented. The model takes into account the fluid-dynamic and mass transfer, in addition to biological phenomena, it being based on fundamental principles. The model has been calibrated and validated using data from a pilot-scale tubular photobioreactor but it can be extended to other designs. It can be used to determine, from experimental measurements, the values of characteristic parameters. The model also allows a simulation of the system's dynamic behaviour in response to solar radiation, making it a useful tool for design and operation optimization of photobioreactors. Moreover, the model permits the identification of local pH gradients, dissolved oxygen and dissolved carbon dioxide; that can damage microalgae growth. In addition, the developed model can map the different characteristic time scales of phenomena inside microalgae cultures within tubular photobioreactors, meaning it is a valuable tool in the development of advanced control strategies for microalgae cultures. © 2011 Elsevier Ltd. All rights reserved. Source


Thompson R.B.,University of Almeria | Gallardo M.,University of Almeria | Rodriguez J.S.,Chapingo Autonomous University | Sanchez J.A.,University of Almeria | Magan J.J.,Estacion Experimental Las Palmerillas
Scientia Horticulturae | Year: 2013

Free-draining soilless culture is commonly used in greenhouses in the Mediterranean Basin, frequently with tomato. Crop N uptake concentration has been proposed as a tool to assist with N management of crops in soilless culture. Three tomato crops were grown in free-draining rockwool to evaluate the relationship of crop N uptake concentration to crop N uptake and NO3 - leaching. The three crops were 2005 spring, 2005 autumn-winter, and 2006 spring crops. Drainage fractions were 24% in each crop. Irrigation and drainage volumes were determined daily. N applied and leached were determined daily in the 2005 spring crop and otherwise weekly. Crop N uptake was determined by difference. Average N concentrations (NO3 --N plus NH4 +-N) in nutrient solution were 9.6, 11.5 and 9.2mmolL-1, and in drainage (N leached) were 14.8, 8.5 and 11.8mmolL-1. The amounts of N leached were 178, 69 and 145kgNha-1. Crop N recoveries were 63, 82 and 69%; unrecovered N was lost by NO3 - leaching. Average N uptake concentrations were 8.6, 12.5 and 8.4mmolL-1. Maintaining the applied N concentration at slightly less than N uptake concentration for much of the crop was associated with a very high crop N recovery (82%) by the 2005 autumn-winter crop. In the two spring crops with lower crop N recoveries (63 and 69%), the average N uptake concentration was higher than the average applied N concentration. The highest N concentrations in drainage occurred when applied N concentration clearly exceeded N uptake concentration. These data demonstrated the potential for using crop N uptake concentration to assist with the formulation of nutrient solutions for soilless crops. © 2012 Elsevier B.V. Source


Dominguez E.,University of Malaga | Fernandez M.D.,Estacion Experimental Las Palmerillas | Hernandez J.C.L.,Estacion Experimental Las Palmerillas | Parra J.P.,Estacion Experimental Las Palmerillas | And 3 more authors.
Physiologia Plantarum | Year: 2012

Fruit cuticle composition and their mechanical performance have a special role during ripening because internal pressure is no longer sustained by the degraded cell walls of the pericarp but is directly transmitted to epidermis and cuticle which could eventually crack. We have studied fruit growth, cuticle modifications and its biomechanics, and fruit cracking in tomato; tomato has been considered a model system for studying fleshy fruit growth and ripening. Tomato fruit cracking is a major disorder that causes severe economic losses and, in cherry tomato, crack appearance is limited to the ripening process. As environmental conditions play a crucial role in fruit growing, ripening and cracking, we grow two cherry tomato cultivars in four conditions of radiation and relative humidity (RH). High RH and low radiation decreased the amount of cuticle and cuticle components accumulated. No effect of RH in cuticle biomechanics was detected. However, cracked fruits had a significantly less deformable (lower maximum strain) cuticle than non-cracked fruits. A significant and continuous fruit growth from mature green to overripe has been detected with special displacement sensors. This growth rate varied among genotypes, with cracking-sensitive genotypes showing higher growth rates than cracking-resistant ones. Environmental conditions modified this growth rate during ripening, with higher growing rates under high RH and radiation. These conditions corresponded to those that favored fruit cracking. Fruit growth rate during ripening, probably sustained by an internal turgor pressure, is a key parameter in fruit cracking, because fruits that ripened detached from the vine did not crack. © Physiologia Plantarum 2012. Source


Magan J.J.,Estacion Experimental Las Palmerillas | Lopez J.C.,Estacion Experimental Las Palmerillas | Granados R.,Estacion Experimental Las Palmerillas | Perez-Parra J.,Estacion Experimental Las Palmerillas | And 3 more authors.
Acta Horticulturae | Year: 2011

Increasing global radiation transmission in Mediterranean greenhouses, especially during the low radiation season, has been reported to be one of the most effective methods to raise the yields and quality of the produce. The east-west orientation improves radiation transmission in the low radiation season, as compared with the north-south orientation, but generates radiation transmission differences between the different zones of the greenhouse. A study on the transmission and spatial uniformity of solar radiation of two east-west oriented greenhouses was conducted in Almeria (Spain). The greenhouses, each with a floor area of 960 m 2 (40×24 m) and a similar volume, were a Venlo type glasshouse, covered with conventional 4 mm glass, and a gothic arch-roofed plastic multispan, covered with 0.2 mm thick plastic film. The radiation transmission data, quantified using linear solarimeters along the transverse section of the spans at the eaves level, show transmission differences across the span section in both greenhouses, during the winter and spring seasons. Global radiation differences between greenhouses were very small, with slightly higher radiation in the glasshouse during the first part of the winter, which reversed later, though the differences continued to be very small. The total and marketable yields of a cucumber crop were higher in the plastic multispan than in the glasshouse; these differences were attributed to the quality of global radiation. The diffusive properties of the plastic cover contributed to a higher content of diffuse radiation in the plastic greenhouse compared with the glasshouse. Source

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