Efecto del glifosato sobre el crecimiento y acumulación de azúcares libres en dos biotipos de lolium perenne de distinta sensibilidad al herbicida

El movimiento sistémico del glifosato está determinado por el transporte de fotoasimilados. A su vez, la capacidad de un destino de consumir los asimilados está condicionada por su actividad metabólica. Pese a su importancia, la relación entre el glifosato y la síntesis de azúcares en hojas fuente ha sido poco abordada. El objetivo del presente trabajo fue evaluar los efectos del glifosato sobre el crecimiento y la acumulación de azúcares libres en dos biotipos de Lolium perenne de baja y alta sensibilidad al herbicida. Se trabajó con clones de ambos tipos de plantas, en macollaje, tratados con 1.440 g e.a. ha-1 de glifosato y sin tratamiento herbicida como controles. Se evaluó periódicamente el efecto del glifosato sobre el rebrote de hojas hasta las 50 horas post-aplicación y sobre los niveles de azúcares libres totales, reductores y no reductores en hojas a 1, 2, 3 y 5 días post-aplicación. A partir de las 25 horas post-aplicación, el glifosato provocó una disminución del crecimiento del 58% en el biotipo susceptible, con una acumulación de azúcares libres superior al 90% con relación al control, desde el primer día post-aplicación en adelante. La inhibición del crecimiento, inducida por el glifosato en plantas susceptibles, no depende de la limitación del traslado de fotoasimilados desde la parte aérea. Por tanto, la acumulación de azúcares libres en hojas podría explicarse por la caída en la tasa de crecimiento. En el biotipo de baja sensibilidad, en el que no se detectó inhibición del crecimiento, estos efectos fueron limitados.The systemic movement of glyphosate is determined by the transport of photoassimilates. In turn, the capacity of a destination to consume assimilates is conditioned by their metabolic activity. Despite its importance, the relationship between the glyphosate and the sugar synthesis from source leaves has been little studied. The aim of this work was to determine the effect of glyphosate on the growth and free sugar accumulation of two Lolium perenne biotypes of low and high glyphosate sensitivity. It was worked with clones of both types, in tillering, sprayed with 1,440 g a.e. ha-1 of glyphosate as treatments and without herbicide as controls. The glyphosate effects on the regrowth of leaves was studied until 50 hours post-application and on total free sugar, reducing free sugar and nonreducing free sugar from leaves to 1, 2, 3 and 5 days post-application were periodically evaluated. From 25 hours after glyphosate application, it caused on the susceptible biotype a growth decrease of 58% and an accumulation of free sugar above 90% compared to controls. In susceptible biotypes, growth inhibition does not depend on a reduced photoassimilate translocation from the overground part. Therefore, the free sugar accumulation in leaves could be explained by the fall in the rate of growth. These effects are limited in the low sensitivity biotype, where growth inhibition has not been detected

Senescence and yield responses to plant density in stay green and earlier-senescing maize hybrids from Argentina

Increases in maize (Zea mays L.) yield over the past few decades have been associated with breeding for tolerance to progressively higher plant densities. Since high plant density exacerbates interplant competition, it has been suggested that improved resource capture through delayed senescence might be advantageous in such situations. The main objectives of this work were to determine (1) the time-course of canopy senescence, (2) post-silking C and N accumulation and (3) yield responses of contemporary maize hybrids with different expression of the stay green (SG) character grown in a range of plant densities from moderate to intense crowding stress. Three experiments consisting of a combination of different plant densities (from 6 to 10 pl m−2) and commercial hybrids with different timing of senescence were carried out. High density accelerated leaf senescence at the lower canopy layer. The SG hybrids delayed senescence and retained green leaves at physiological maturity at all tested densities. One of these hybrids (NK880), with a strong SG character, retained green leaves at all canopy layers, even at the lower layer exposed to limiting irradiance. Lower canopy leaves maintained high respiratory rates in NK880, while leaves of the NSG hybrid (DK682) senesced and their respiration became not detectable. At the highest tested density, the NSG DK682 achieved greater grain yields than the SG NK880. Increased density reduced kernel weight (KW), and this decrease was more pronounced for the SG NK880 (6–18% comparing 10 vs. 8 pl m−2). In spite of delayed senescence in NK880, no hybrid differences were found for post-silking dry matter accumulation and plant dry matter at physiological maturity. Unexpectedly, plant nitrogen content (Nc) at harvest was similar (Exp. I) or even lower (P < 0.05, Exp. II) in the SG NK880. This was the result of lower net N accumulation during the post-silking period (Exp. I) or lower Nc achieved at silking (Exp. II) in the SG NK880. A strong positive relation was found between KW and N concentration in kernels, with %N in kernels being below the critical N concentration to achieve potential KW (around 1.4%) in the SG hybrid. This suggests that yield in NK880 was limited by N. In the SG genotype, N remobilization from vegetative organs did not seem to compensate for the N deficit for optimum grain growth. In summary, at high densities the NK880 hybrid displayed a strong, constitutive SG character, even if it accumulated less N, and senescence delay was not reflected in higher grain yield.Fil: Antonietta, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Fisiología Vegetal; Argentina; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; ArgentinaFil: Fanello, Diego Darío. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Fisiología Vegetal; Argentina; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; ArgentinaFil: Acciaresi, H. A.. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; ArgentinaFil: Guiamet, Juan Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Fisiología Vegetal; Argentina; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentin

Extensão bivariada do índice de confiabilidade univariado para avaliação da estabilidade fenotípica Bivariate extension of univariate reliability index for evaluating phenotypic stability

Com o presente trabalho, objetiva-se realizar a derivação teórica da extensão bivariada dos métodos de Annicchiarico (1992) e Annicchiarico et al. (1995) para estudar a estabilidade fenotípica. A partir dos ensaios com <img src="/img/revistas/cagro/v28n5/a11res01.gif" align=texttop>genótipos em <img src="/img/revistas/cagro/v28n5/a11res02.gif" align=texttop>ambientes e mensurações de duas variáveis, cada genótipo teve seu valor padronizado com relação a cada variável k = 1, 2. Essa padronização foi realizada em função da média do ambiente, da seguinte forma: Wijk = Yijk/<img src="/img/revistas/cagro/v28n5/a11res03.gif" align=top>&#215;100 ; em que Wijk representa o valor padronizado do genótipo i, no ambiente j para a variável k; <img src="/img/revistas/cagro/v28n5/a11res04.gif" align=top>representa a média observada do genótipo <img src="/img/revistas/cagro/v28n5/a11res05.gif" align=texttop>, no ambiente <img src="/img/revistas/cagro/v28n5/a11res06.gif" align=texttop>para a variável k e <img src="/img/revistas/cagro/v28n5/a11res07.gif" align=texttop>, a média de todos genótipos para o ambiente <img src="/img/revistas/cagro/v28n5/a11res06.gif" align=texttop>e variável k. Com os valores padronizados foram estimados o vetor média e a matriz de variância e covariância de cada genótipo. Foi obtida a derivação teórica da extensão bivariada do índice de risco (Ii) de Annicchiarico com sucesso e foi proposto um segundo índice de risco baseado nas probabilidades bivariada (Prb i); os dois índices apresentaram grande concordância nos resultados obtidos em um exemplo ilustrativo com genótipos de melões.<br>The objective of this work was to obtain the theoretical derivation of the bivariate extension to the methods proposed by Annicchiarico (1992) and Annicchiarico et al. (1995) for studing phenotypic stability. Considering assays with <img src="/img/revistas/cagro/v28n5/a11res01.gif" align=texttop>genotypes in <img src="/img/revistas/cagro/v28n5/a11res02.gif" align=texttop>environments and two variates, every genotype had the response of each variate (k = 1, 2) standardized. This standardization has been made using the environment means as follows: Wijk = Yijk/<img src="/img/revistas/cagro/v28n5/a11res03.gif" align=top>&#215;100 ; where Wijk represents the ith genotype standard value in the jth environment for the kth variate; <img src="/img/revistas/cagro/v28n5/a11res04.gif" align=top>represents the observed mean of the ith genotype, in jth environment for the kth variate e <img src="/img/revistas/cagro/v28n5/a11res07.gif" align=texttop>the overall genotypes means for jth environment to kth variate. Considering the standardized values, the genotypes mean vector and covariance matrix were estimated. The theoretical derivation of the bivariate reliability index (Ii) of Annicchiarico was wasked out and a second risk index was proposed based on the bivariate probabilities (Prb i); the two indexes proposed has shown good agreement to the results in an example with melon genotypes

Climate change and the potential spread of Sorghum halepense in the central area of Argentina based on growth, biomass allocation and eco-physiological traits

Despite the research dedicated to understand the potential climate change impacts on cropping systems, little attention has been given to potential effects on the geographic range of agricultural weeds. This paper reviews some biological and eco-physiological features of Sorghum halepense populations and their current and potential spread in a central eco-region of Argentina. Above ground biomass accumulation of the weed shows very high accumulation rates, which in the case of rhizomes is boosted as the available resources in propagule increases. An increase in temperature by 15 % may increase the relative growth rate (RGR) by 50 % in a 20–90 days growth period. Not only biomass output but also biomass allocation is directly related to adaptation in changing environments. Populations adapted to limited water conditions are able to maintain a higher RGR under water restriction as compared to those adapted to more humid conditions. Regarding the temperature, climate models are coincident: a range of increase from 0.9 °C in the south to 1.4 °C in the north of Argentina is predicted for 2020–2040, as compared to the period 1961–1990. Concerning the rainfall, not yet a prediction but a real fact is the displacement of isohyets from east to south. The average frequency of the weed in the pool of fields recently surveyed in the central region was 37 %, which increased to 42 % in the field borders. We consider that this frequency is high, since all crop fields are managed with high technology level and herbicides have been applied not only during the crop cycles, but also in previous fallows. The high RGR and other physiological features of weed populations at low water availability, which is more frequent in the west of the surveyed region where the frontier of extensive crops have recently displaced, may explain higher frequencies found. Well-adapted S. halepense populations invading rainfed crops in this eco-region will likely to take advantage under the forthcoming forecasted climatic conditions. Since temperatures increase from east to west as shown in climograms, S. halepense populations will likely perform even better under the new climate conditions. Coupling the actual management to physiological traits, it is envisaged an increase of the weed frequency in the surveyed eco-regions.Facultad de Ciencias Agrarias y Forestale

SiPP (Stroke in Pregnancy and Postpartum): A prospective, observational, international, multicentre study on pathophysiological mechanisms, clinical profile, management and outcome of cerebrovascular diseases in pregnant and postpartum women

Rationale: Cerebrovascular diseases associated with pregnancy and postpartum period are uncommon; however, they can have an important impact on health of both women and foetus or newborn. Aims: To evaluate the frequency, characteristics and management of cerebrovascular events in pregnant/postpartum women, to clarify pathophysiological mechanisms underlying the occurrence of these events including biomolecular aspects, and to assess the short- and long-term cerebrovascular and global cardiovascular outcome of these patients, their predictors and infant outcome. Methods and design: This is an observational, prospective, multicentre, international case–control study. The study will include patients with cerebrovascular events during pregnancy and/or within six months after delivery. For each included case, two controls will be prospectively recruited: one pregnant or puerperal subject without any history of cerebrovascular event and one non-pregnant or non-puerperal subject with a recent cerebrovascular event. All controls will be matched by age, ethnicity and type of cerebrovascular event with their assigned cases. The pregnant controls will be matched also by pregnancy weeks/trimester. Follow-up will last 24 months for the mother and 12 months for the infant. Summary: To better understand causes and outcomes of uncommon conditions like pregnancy/postpartum-related cerebrovascular events, the development of multisite, multidisciplinary registry-based studies, such as the Stroke in Pregnancy and Postpartum study, is needed in order to collect an adequate number of patients, draw reliable conclusions and give definite recommendations on their management. © European Stroke Organisation 2019

SiPP (Stroke in Pregnancy and Postpartum): A prospective,observational, international, multicentre study on pathophysiological mechanisms, clinical profile, management and outcome of cerebrovascular diseases in pregnant and postpartum women

Abstract Rationale: Cerebrovascular diseases associated with pregnancy and postpartum period are uncommon; however, they can have an important impact on health of both women and foetus or newborn. Aims: To evaluate the frequency, characteristics and management of cerebrovascular events in pregnant/postpartum women, to clarify pathophysiological mechanisms underlying the occurrence of these events including biomolecular aspects, and to assess the short- and long-term cerebrovascular and global cardiovascular outcome of these patients,their predictors and infant outcome. Methods and design: This is an observational, prospective, multicentre, international case–control study. The study will include patients with cerebrovascular events during pregnancy and/or within six months after delivery. For each included case, two controls will be prospectively recruited: one pregnant or puerperal subject without any history of cerebrovascular event and one non-pregnant or non-puerperal subject with a recent cerebrovascular event. All controls will be matched by age, ethnicity and type of cerebrovascular event with their assigned cases. The pregnant controls will be matched also by pregnancy weeks/trimester. Follow-up will last 24 months for the mother and 12 months for the infant. Summary: To better understand causes and outcomes of uncommon conditions like pregnancy/postpartum-related cerebrovascular events, the development of multisite, multidisciplinary registry-based studies, such as the Stroke in Pregnancy and Postpartum study, is needed in order to collect an adequate number of patients, draw reliable conclusions and give definite recommendations on their management. © European Stroke Organisation 2019