Caracterización Termofisiológica del Ritmo de Absorción de Nutrientes del Melón (Cucumis Melo L. Var reticulatus Naud)

Se estudiaron datos de absorción mineral de tres experimentos diferentes e independientes, separados espacial y temporalmente, dos bibliográficos y uno original. Este se estableció entre agosto de 1998 y enero de 1999 a 15 km al nor-este de la ciudad de Curicó, Séptima Región, Chile (LAT: -34,9833; LON: -71,2333) para obtener la absorción de nutrientes del melón cultivado en cuatro macrotúneles con fertirrigación, en una densidad de plantación de 3,09 pl·m-2. Se analizó periódicamente el contenido de N, P, K, Ca, Mg y biomasa de las plantas hasta 90 días después del trasplante. La producción total de biomasa fue 1,95 kg·m-2 y el total de macronutrientes absorbidos fue g·m-2 : 37,8 de N; 8,4 de P; 64,5 de K; 42,4 de Ca y 6,5 de Mg. Se determinó la integral térmica del cultivo y se estableció la tasa de absorción termofisiológica en escala de tiempo térmico (tautocrón = 59,9) así como la absorción en escala cronológica. La tasa de absorción termofisiológica mostró una evolución similar a la tasa de absorción cronológica debido a que el cultivo se mantuvo cercano a la temperatura óptima, evidenciándose esto en una relación lineal entre tiempo térmico y cronológico. Los datos de este ensayo fueron relacionados con los dos experimentos bibliográficos, encontrándose que la utilización de una escala de tiempo térmico para la tasa de absorción de nutrientes así como para la absorción acumulada en situaciones disímiles, es un procedimiento más exacto que la simple utilización del tiempo cronológico

Determinación alométrica entre absorción mineral y biomasa en diferentes especies cultivadas

Se determinó los coeficientes de ajuste para relacionar la absorción relativa de nutrientes y la biomasa relativa en siete diferentes cultivos hortícolas y frutales, empleando la ecuación potencial, M·MT-1 = MO (B·BT-1 ) b (M = cantidad de nutriente en la biomasa del cultivo, B; MT = nutrientes totales contenidos en la biomasa total BT; MO= constante de normalización, b = exponente alométrico). Se examinó datos de absorción de nutrientes y biomasa de diferentes experimentos previamente publicados. Los indicadores de bondad de ajuste mostraron que esta función relacionó satisfactoriamente ambas variables. En los diferentes casos la suma de cuadrados absoluta varió entre 0,0009 y 0,084 y la desviación estándar de los residuos varió entre 0,008 y 0,2 sobre el ajuste de valores relativos. Siempre se obtuvo valores de coeficiente de correlación mayores a 0,9. Junto a la determinación del exponente alométrico para macronutrientes, se encontró que la constante MO se aproximó a la unidad, pudiendo asumirse igual a 1,0. El exponente alométrico b caracterizó la curvatura para cada nutriente

Nonlinear Allometric Equation for Crop Response to Soil Salinity

Crop response to soil salinity has been extensively studied, from empirical works to modelling approach, being described by different equations, first as a piecewise linear model. The equation employed can differ with actual response, causing miscalculation in practical situations, particularly at the higher extremes of the curve. The aim of this work is to propose a new equation, which allows determining the full response to salinity of plant species and to provide a verification using different experimental data sets. A new nonlinear equation is exposed supported by the allometric approach, in which the allometric exponent is salinity-dependent and decreases with the increase in relative salinity. A conversion procedure of parameters of the threshold-slope model is presented; also, a simple procedure for estimating the maximum salinity (zero-yield point) when data sets are incomplete is exposed. The equation was tested in a wide range of experimental situations, using data sets from published works, as well as new measurements on seed germination. The statistical indicators of quality (R2, absolute sum of squares and standard deviation of residuals) showed that the equation accurately fits the tested empirical results. The new equation for determining crop response to soil salinity is able to follow the response curve of any crop with remarkable accuracy and flexibility. Remarkable characteristics are: a maximum at minimum salinity, a maximum salinity point can be found (zero-yield) depending on the data sets, and a meaningful inflection point, as well as the two points at which the slope of the curve equals unity, can be found

Physiological and biochemical responses to the exogenous application of proline of tomato plants irrigated with saline water

In scope of crop salinity tolerance, an experiment was carried out in a field using saline water (6.57 dS m−1) and subsurface drip irrigation (SDI) on two tomato cultivars (Solanum lycopersicum, cv. Rio Grande and Heinz-2274) in a salty clay soil. Exogenous application of proline was done by foliar spray at two concentrations: 10 and 20 mg L−1, with a control (saline water without proline), during the flowering stage. Significant higher increases in proline and total soluble protein contents, glutamine synthetase (GS, EC6.3.1.2) activities and decreases in proline oxidase (l-proline: O2 Oxidoreductase, EC1.4.3.1) activities were detected in both tomato cultivars when irrigated with saline water (6.57 dS m−1) and exogenously applied by the lower concentration of proline. Taking in consideration the obtained results, it was concluded that the foliar spray of low concentration of proline can increase the tolerance of both cultivars of tomato to salinity under field conditions

Effect of electromagnetic treatment of saline water on soil and crops

Two experiments were carried out to study the effect of the electromagnetic treatment of saline water on seed germination of corn and the response of soil and potato crop irrigated with such water. The experiments were performed under controlled conditions with different water quality and soil texture. The electromagnetic water treatment was applied using Aqua-4D physical water treatment device. Results showed a significant increase in germination rate of corn seedlings watered with electromagnetic-treated saline water (EC = 4 dS m−1), particularly when water was exposed to electromagnetic fields for 15 min. The experiments carried on potato crop with two soil textures, showed a significant increase in tuber yield when irrigated with electromagnetic treated water. It was also observed a significant decrease of soil salinity (ECe), Na+ and Cl− contents of soils irrigated with electromagnetic treated saline water compared to the soils irrigated with non-treated saline water. In contrast, compared to both treatments (control treatment and saline water treatment), the electromagnetic saline water treatment produced non-significant effect on tuber yield, Mg2+ and HCO3-. However, the electromagnetic treatment of saline water increased significantly K+, N and P adsorption in all tissues of potato and decreased significantly the adverse effects of saline water. Based on our results, electromagnetic treatment of saline water can reduce the negative effect of salinity on corn germination and potato crop and increase yield in about 10% in test conditions. Keywords: Electromagnetic water treatment, Seed germination, Potatoes, Tunisia, Salinit

Solvothermal Synthesis of Platinum Alloy Nanoparticles for Oxygen Reduction Electrocatalysis

Platinum alloy nanoparticles show great promise as electrocatalysts for the oxygen reduction reaction (ORR) in fuel cell cathodes. We report here on the use of <i>N</i>,<i>N</i>-dimethylformamide (DMF) as both solvent and reductant in the solvothermal synthesis of Pt alloy nanoparticles (NPs), with a particular focus on Pt–Ni alloys. Well-faceted alloy nanocrystals were generated with this method, including predominantly cubic and cuboctahedral nanocrystals of Pt₃Ni, and octahedral and truncated octahedral nanocrystals of PtNi. X-ray diffraction (XRD) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), coupled with energy dispersive spectroscopy (EDS), were used to characterize crystallite morphology and composition. ORR activities of the alloy nanoparticles were measured with a rotating disk electrode (RDE) technique. While some Pt₃Ni alloy nanoparticle catalysts showed specific activities greater than 1000 μA/cm²_Pt, alloy catalysts prepared with a nominal composition of PtNi displayed activities close to 3000 μA/cm²_Pt, or almost 15 times that of a state-of-the-art Pt/carbon catalyst. XRD and EDS confirmed the presence of two NP compositions in this catalyst. HAADF-STEM examination of the PtNi nanoparticle catalyst after RDE testing revealed the development of hollows in a number of the nanoparticles due to nickel dissolution. Continued voltage cycling caused further nickel dissolution and void formation, but significant activity remained even after 20 000 cycles