Physiology

Research of the physiology section was centered on identifying the characters associated with high root yields and quality in cassava under stress conditions. Plant reaction to water stress was studied, specifically regarding growth and yields of var. M Mex 59 and M Col 22 with a period of artificial rain exclusion. Observations were made throughout the stress period and subsequent recovery. Water stress reduced LAI notably although M Mex 59 maintained a LAI approx. twice that of M Col 22 during the stress period. LAI for both var. increased during recuperation and by final harvest (10 mo.) they were similar in both control and stressed plants. DM and starch contents increased during the stress period but decreased during recuperation. (CIAT)El enfasis de las investigaciones de la seccion de fisiologia se centro en la identificacion de los caracteres asociados con un alto rendimiento y calidad de las raices en condiciones de estres. Se estudiaron las reacciones de la planta a la sequia, especificamente el desarrollo y los rendimientos de las var. M Mex 59 y M Col 22 en un periodo de sequia artificial. Las observaciones se realizaron durante los periodos de sequia y de recuperacion posterior. La sequia redujo notablemente el IAF, aunque M Mex 59 mantuvo un IAF aprox 2 veces mayor que M Col 22 durante el periodo de estres. Durante el periodo de recuperacion los IAF aumentaron para ambas var.; en el momento de la cosecha (10 meses), los IAF fueron similares con los de las plantas testigo. Los contenidos de MS y de almidon se incrementaron durante el periodo de sequia pero disminuyeron en el periodo de recuperacion. (CIAT

Modelling rankings in R: the PlackettLuce package

This paper presents the R package PlackettLuce, which implements a generalization of the Plackett-Luce model for rankings data. The generalization accommodates both ties (of arbitrary order) and partial rankings (complete rankings of subsets of items). By default, the implementation adds a set of pseudo-comparisons with a hypothetical item, ensuring that the underlying network of wins and losses between items is always strongly connected. In this way, the worth of each item always has a finite maximum likelihood estimate, with finite standard error. The use of pseudo-comparisons also has a regularization effect, shrinking the estimated parameters towards equal item worth. In addition to standard methods for model summary, PlackettLuce provides a method to compute quasi standard errors for the item parameters. This provides the basis for comparison intervals that do not change with the choice of identifiability constraint placed on the item parameters. Finally, the package provides a method for model-based partitioning using covariates whose values vary between rankings, enabling the identification of subgroups of judges or settings that have different item worths. The features of the package are demonstrated through application to classic and novel data sets.Comment: In v2: review of software implementing alternative models to Plackett-Luce; comparison of algorithms provided by the PlackettLuce package; further examples of rankings where the underlying win-loss network is not strongly connected. In addition, general editing to improve organisation and clarity. In v3: corrected headings Table 4, minor edit

Photosynthetic pigment levels in Macroptilium lathyroides L under water deficit.

Título em espanhol: Contenido de pigmentos fotosinteticos Macroptilium lathyroides L en condiciones de sequia

La Distribució geogràfica i ecològica dels bivalves d'aigua dolça recents dels Països Catalans

Aquesta és una compilació de 684 citacions (163 de les quals són noves) de les 18 espècies de bivalves d'aigua dolça recents dels Països Catalans. Donada la varietat de mètodes de recol•leccio i de les citacions publicades, només es mencionen presències en cadascuna de les 412 localitats prospectades. També es fa esment del tipus d'habitat, si és conegut. Totes les localitats es troben ordenades per conques hidrogràfiques.This is a compilation of 684 records (163 of them new) of the 18 species of Recent freshwater Bivalves in the Catalan Countries. Given the variety of collecting techniques and published accounts, only presences in each of the 412 localities are recorded. The kind of habitat involved in each case is also mentioned, if known. All localities are arranged by hydrographic drainages

Maize grain yield response to changes in acid soil characteristics with yearly leguminous crop rotation, fallow, slash, burn and liming practices

Open Access JournalAn experiment was conducted for 4 years to assess the effectiveness of fallow, slash and burn farming systems on maize grain yield and soil chemical characteristics. It was also meant to measure the response to yearly rotation of maize and leguminous crops (cowpea and mucuna), as options for managing the acidity of the soil of the study site. The maize tolerant cultivar (cvr) out yielded the sensitive cvr and the farmers’ variety by 43% and 16% respectively. On the maize/grain legume rotation plots, the tolerant and sensitive cvr yielded 5% and 7% respectively more than their corresponding yields on plots with fallow, slash and burn rotation. Maize/grain legume rotation demonstrated one of the least soil acidifications, exhibiting the least increase in exchangeable Al (23%), H (24%), and Al saturation (5%) resulting in improved soil fertility through increase in available Ca (2%), Mg (85%), P (75%), and CEC (14%). The fallow, slash and burn rotation, associated with the tolerant cvr showed similar grain yield with grain legume rotation, but contributed more to soil acidification. Maize/leafy legume rotation gave a similar yield to the above mentioned practices. The yearly application of 250 kg ha-1 of dolomitic lime for four consecutive years did not result in significant changes in soil characteristics and grain yield especially for the Al tolerant cvr. However, application of 2250 kg ha-1 of lime neutralized the Al toxicity, regardless of the rotation scheme. The study concluded that the four years maize cultivation through fallow/ slash and burn rotation extensively used in the humid forest zone is not the best option on acid soil

La continuidad de una obra medieval: azud, acequias, molinos y pesquera del Bajo Ebro en la época del Renacimiento

Peer Reviewe

¿Castañar para fruto o para madera? Consideraciones sobre su autoecología.

The autoecology of species has provided quantified information on the characteristics of the environment in which forest species grow. These studies have been carried out using research done on a regional basis, and the study of the sweet chestnut represents the first case that has arisen of the same species appearing in two such very different ways. The chestnut has been exploited by man since ancient times and continues to be of use to humans today as a source of edible chestnuts and/or timber production. This work examines the differences in autoecological characteristics between chestnut stands for the production of nuts and timber. The results indicate that chestnut orchards in Spain tend to be located at higher altitudes and on sites with a less pronounced slope than for trees used for timber production. Chestnut orchards are located under climates with greater winter precipitation, lower summer precipitation and greater excess precipitation, as well as lower average annual temperatures and potential evapotranspiration. From the soil point of view the orchards are found in soils which are significantly less sandy, more silty and clayey, and with a significantly lower permeability, as well as a greater water-holding capacity. Taking the whole set of ecological parameters analysed, it can be seen that it is not the soil or physiographic characteristics but rather the climatic characteristics which basically determine the use which the chestnut stands will be given. It therefore seems appropriate to continue using these climatic characteristics as a guide when assigning the most suitable use for a chestnut stand, whether for the production of nuts or timber