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Aim of study: The objective of this study was to present statistical information pertaining to recurrent inconsistencies found in the literature of the last 25 years that involve calculation of the GR and the errors that this may entail when interpreting the seed vigor of different botanical materials.Materiales y métodos: After filtering articles that did not present numerical results or in which the application of Maguire's formula was not clearly indicated, a total of 124 papers were ultimately used in this study.Main results: Germination rate (GR) represents the potential of seeds to germinate and, along with germination percentage (GP), are the two most important measurements when evaluating seed quality. The correct calculation of GR allows the seeds classification according to their vigor and capacity to produce healthy seedlings, so it is very important to rely on the adequate mathematical formula for this purpose. According to the formula developed by Maguire, this parameter is calculated by the sum of values obtained when dividing the GP at different times (i.e. daily) by the total time elapsed since the start of the test. We have found from the relevant literature that different authors have been using different ways of applying the formula, which makes it difficult to directly compare the results.Research highlights: A total of 54.8 % of the papers reviewed, belonging mainly to the theme of forestry, presented objectionable application of the formula. Publication of this warning may help to reduce the occurrence of this situation in the future.Keywords. Germination percentage, germination speed, Maguire’s formula, seed vigor.

Background: Ormosia macrocalyx is a tropical forest tree classified as endangered. Its seeds experience problems of dispersion and apparent physical dormancy due to their hard seed coating. Hypotheses: 1) The stages of dehiscence of the fruits of Ormosia macrocalyx influence the germinative behavior of its seeds. 2) Pregerminative treatments will improve the germination process of the seeds stored under refrigeration. Study species: Ormosia macrocalyx Study site and period: Villahermosa, Tabasco, Mexico from October 2012 to October 2014 Methods: Two completely randomized experiments were conducted in order to analyze the germination process by 1) evaluating germination in seeds from fruit at three stages of dehiscence (closed, semi-open, and open fruit) and 2) applying four treatments, including three pregerminative treatments (water soaking for 24 h, mechanical scarification and scarification+1% gibberellic acid) plus an untreated control, to seeds stored under refrigeration for 17 months. Results: Differences were found in germination rate (GR), corrected germination rate (CGR) and time to attain 50 % germination (T 50 ) among treatments in the first experiment, with the seeds from open fruits presenting the lowest response (3.31 % day -1 for GR and CGR, and 15.8 days for T 50 ), although all treatments showed similar times for the initiation of germination (GI) and final germination percentage (GP). In the second experiment, the effect of scarification was greater than both the control and soaking treatments. Scarification treatment values were 68.0 % (GP), 12.0 days (GI), 4.53 % day -1 (GR), 6.65 (CGR) and 14.5 days (T 50 ). Addition of gibberellic acid did not produce any further advantage over scarification alone. Conclusions:Seeds from open fruits have lower germination rates, although the final GP is not affected. Stored seeds present physical dormancy but lose viability with storage and, when collected after remaining attached to the tree for undefined periods, scarification can greatly improve their germination rate. Key words: fruit maturation, dormancy, pregerminative treatments, storage Germinación de semillas de Ormosia macrocalyx, un árbol forestal amenazado ResumenAntecedentes: Ormosia macrocalyx es un árbol tropical amenazado. Sus semillas tienen problemas de dispersión y aparente latencia física por cubierta seminal dura. Hipótesis: 1) Las etapas de dehiscencia de los frutos de Ormosia macrocalyx repercutirán en el comportamiento germinativo de sus semillas. 2) Los tratamientos pregerminativos mejorarán el proceso germinativo de las semillas almacenadas en refrigeración Especie de estudio: Ormosia macrocalyx Ducke. Sitio de estudio y fechas: Villahermosa, Tabasco, México, octubre 2012-octubre 2014 Métodos: Se establecieron dos experimentos completamente aleatorios para analizar el proceso de la germinación: 1) Evaluación de la germinación en semillas de frutos en tres estados de madurez (cerrados, semi-abiertos y abiertos), y 2) Aplicación de cuatro tratamientos, tres pregerminativos (r...

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ResumenLos productos del sector agroalimentario tienen una característica principal, la volatilidad de los precios, producto de varios factores, entre ellos: la oferta, demanda, crecimiento de la población, variables biológicas y fenómenos naturales que inciden en la productividad, porque el mercado responde a demandas colectivas de consumidores y productores. Con el fin de planificar racionalmente la toma de decisiones basado en pronósticos confiables, tomando la variable econométrica precios se utilizó la metodología Box-Jenkins a fin de aplicar el modelo econométrico ARIMA (1,0,1), para ajustar el comportamiento de la serie de tiempo de los precios internacionales del arroz durante el período comprendido entre junio 2002 a noviembre 2012. La predicción mediante el modelo econométrico ajustado indicó precios de US $648 por tonelada el primer mes de estimación y US $665 por tonelada a los 16 meses; es decir, diciembre 2014. En este período, la estimación de los precios arrojó valores en las bandas superior e inferior de US $191.7 y 2 309.7 por tonelada, respectivamente. Se observó que el modelo es muy útil como predictor, refleja el comportamiento del proceso estocástico generado por la serie de datos.Palabras claves: Box-Jenkins, predicción, series de tiempo. AbstractThe agri-food products have a main feature, the price volatility due to various factors, including: supply, demand, population growth, biological variables and natural phenomena that affect productivity, because the market responds to collective demands of consumers and producers. In order to rationally plan decisions based on reliable forecasts, using econometric prices varying the Box-Jenkins methodology was used to implement the econometric model ARIMA (1,0,1), to adjust the behaviour of the series time international rice prices during the period from June 2002 to November 2012. The prediction using econometric model adjusted indicated prices US $ 648 per tonne in the first month of estimation and US $ 665 per tonne at 16 months; i.e. December 2014. In this period, the estimated prices returned values in the upper and lower bands of US $ 191.7 309.7 per ton and 2, respectively. It was observed that the model is very useful as a predictor, reflects the behaviour of the stochastic process generated by the data series.

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