Physiological responses and post - stress recovery in field - grown maize exposed to high temperatures at flowering

Neiff, Nicolás. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Departamento de Producción Vegetal. Corrientes, Argentina.Ploschuk, Edmundo Leonardo. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cultivos Industriales. Buenos Aires, Argentina.Valentinuz, Oscar. Instituto Nacional de Tecnología Agropecuaria (INTA). Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná (EEA Paraná). Paraná, Entre Ríos. Argentina.Andrade, Fernando Héctor. Instituto Nacional de Tecnología Agropecuaria (INTA). Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce (EEA Balcarce). Balcarce, Buenos Aires, Argentina.2053-2061Heat stress affects physiological traits and biomass production in major crops, including maize. We researched the responses of maximum efficiency of photosystem II (Fv/Fm), relative cell injury (RCI), stomatal conductance (gs), internal CO2 concentration (Ci), leaf photosynthesis (CER), and crop growth rate (CGR) in two maize cultivars exposed to high temperatures around silking (R1) under field conditions. Temperature regimes (i.e. control and heat) were performed during the pre-silking (–15d R1 to R1) and post-silking (R1+2d to R1+17d) periods. In the heat treatments, polyethylene shelters were used in order to increase daytime temperatures around midday (from 10 A.M. to 2 P.M.) during each period (i.e., pre- and post-silking). In the control treatments, the shelters remained open during the entire growing season. Gas exchange variables, Fv/Fm and relative cell injury (RCI) were measured on ear leaves. CGR was estimated based on biomass samples. CER and Fv/Fm presented maximum reductions at the end of the daytime heating. However, 30 min after the shelters were reopened, Fv/Fm of heated leaves reached values similar to controls, which were closely linked to CER recoveries. RCI was negatively associated with Fv/Fm, and cell injury increased gradually as heating continued. Ci was unaffected by heat treatment, indicating that gs was not the primary cause of CER reduction. Heat stress decreased CGR, and the reduction was positively associated with CER and Fv/Fm in both heating periods. We attempted to scale from cell to crop level and identify some physiological traits that could be helpful in breeding programs for heat stress tolerance

Harvest date modifies seed quality and oil composition of Jatropha curcas growth under subtropical conditions in Argentina

One of the most currently promoted new crops for biodiesel productions the perennial species Jatropha curcas L. (Euphorbiaceae) due to its promising high seed yields with high oil concentrations (33–39%) and oil quality that reaching the international biodiesel standards. Although there have been different evaluations of genotypes growing under the same environmental conditions, revealing great variability for seed and oil quality, no reports are available about the effect environmental conditions during grain filling over such traits. The objectives of this work were to determine (i) the effect of harvest dates on seed quality and oil concentration, (ii) if such changes can be explained by the average temperature during grain filling and (iii) how harvest dates could affect biodiesel quality. An experiment was carried out during 29 months in experimental plots located in Formosa, Argentina. A systematic fruit harvest was conducted during 15 different dates on 10 plants with similar height (≈1.80m). Environmental conditions during the experiment were appropriate to create a broad individual seed weight range (326–752mg) and significant differences were found among harvest dates. Seed oil concentrations were significantly different among harvest dates with a maximum value of 38.7±0.6% on 08 August 2011 and a minimum of 19.6±1.8% on 17 March 2010. Oil concentration increased linearly as seed weight increased up to a value of 605mg, after which higher seed weight was not associated with greater seed oil concentration. Oil concentration was largely (r2=0.85) explained by the kernel percentage through a linear regression (y=−25.9+0.967x). Variations in seed weight and oil concentration were not associated with changes in average temperature during grain filling, suggesting that fluctuations in the source-sink relation through the growing season could explain the variations found among harvest dates. Temperature during seed filling period strongly affected oil composition and higher temperatures were associated with higher oleic acid and lower linoleic acid concentrations, although this effect generated only small effects on the biodiesel quality. Environmental conditions during grain filling modified seed quality and oil composition, while its concentration was not affected. This work reveals the existence of harvest dates effects on seed quality and oil concentration, although unrelated with the environmental conditions explored during grain filling period

LA INFLUENCIA DE LAS CONEXIONES VASCULARES XILEMÁTICAS DURANTE LA DETERMINACIÓN DEL MOMENTO DE COSECHA EN MAÍZ TARDÍO

En Argentina, el cultivo de maíz tardío se practica con bastante frecuencia para evitar que la floración ocurra durante un período de sequía, pero los productores se ven obligados a mantener el cultivo durante gran parte del otoño e invierno para lograr que los granos alcancen la madurez comercial. El objetivo de este trabajo fue avanzar en el conocimiento acerca del rol de la conexión xilemática en el proceso de pérdida de humedad de los granos, para lograr una mejor eficiencia de cosecha. Para ello se realizó un experimento de campo con dos tratamientos: uno testigo y otro con la base de la espiga cortada para interrumpir la conexión xilemática durante la ventana de cosecha. En ambos tratamientos, los rendimientos oscilaron los 10000 kg ha-1, pero la tasa de pérdida de la humedad relativa y absoluta durante la primera fase de desecado fue significativamente mayor en el tratamiento cortado. Esto determinó que la remoción de la conexión xilemática lograra alcanzar la madurez comercial a los 65 días de iniciada la ventana de cosecha, a diferencia del testigo cuya humedad era 10 puntos superior. Este trabajo proporciona una nueva base teórica para seleccionar y mejorar cultivares de maíz adecuados para la cosecha mecánica de granos.In Argentina, the cultivation of late-season corn is frequently practiced to avoid flowering during a drought period, but farmers are forced to maintain the crop through much of the autumn and winter to ensure that the grains reach commercial maturity. The objective of this study was to advance the understanding of the role of xylem connection in the grain moisture loss process, in order to achieve a better harvesting efficiency. For this purpose, a field experiment was conducted with two treatments: a control group and another with the base of the cob cut to interrupt the xylem connection during the harvesting window. In both treatments, yields ranged around 10,000 kg/ha, but the rate of relative and absolute moisture loss during the initial drying phase was significantly higher in the cut treatment. This resulted in the xylem connection removal achieving commercial maturity 65 days after the start of the harvesting window, in contrast to the control where moisture content was 10 points higher. This study provides a new theoretical basis for selecting and improving maize cultivars suitable for mechanical grain harvesting.Na Argentina, o cultivo de milho tardio é frequentemente praticado para evitar que a floração ocorra durante um período de seca, mas os produtores são obrigados a manter a cultura durante grande parte do outono e inverno para garantir que os grãos atinjam a maturidade comercial. O objetivo deste estudo foi avançar na compreensão do papel da conexão do xilema no processo de perda de umidade dos grãos, visando a obter uma melhor eficiência na colheita. Para isso, um experimento de campo foi realizado com dois tratamentos: um grupo de controle e outro com a base da espiga cortada para interromper a conexão do xilema durante a janela de colheita. Em ambos os tratamentos, os rendimentos variaram em torno de 10.000 kg/ha, mas a taxa de perda de umidade relativa e absoluta durante a fase inicial de secagem foi significativamente maior no tratamento cortado. Isso resultou na remoção da conexão do xilema, alcançando a maturidade comercial 65 dias após o início da janela de colheita, em contraste com o grupo de controle, onde o teor de umidade estava 10 pontos mais alto. Este estudo fornece uma nova base teórica para selecionar e melhorar cultivares de milho adequados para a colheita mecânica de grãos

Waterlogging of Winter Crops at Early and Late Stages: Impacts on Leaf Physiology, Growth and Yield

Waterlogging is expected to increase as a consequence of global climate change, constraining crop production in various parts of the world. This study assessed tolerance to 14-days of early- or late-stage waterlogging of the major winter crops wheat, barley, rapeseed and field pea. Aerenchyma formation in adventitious roots, leaf physiological parameters (net photosynthesis, stomatal and mesophyll conductances, chlorophyll fluorescence), shoot and root growth during and after waterlogging, and seed production were evaluated. Wheat produced adventitious roots with 20–22% of aerenchyma, photosynthesis was maintained during waterlogging, and seed production was 86 and 71% of controls for early- and late-waterlogging events. In barley and rapeseed, plants were less affected by early- than by late-waterlogging. Barley adventitious roots contained 19% aerenchyma, whereas rapeseed did not form aerenchyma. In barley, photosynthesis was reduced during early-waterlogging mainly by stomatal limitations, and by non-stomatal constraints (lower mesophyll conductance and damage to photosynthetic apparatus as revealed by chlorophyll fluorescence) during late-waterlogging. In rapeseed, photosynthesis was mostly reduced by non-stomatal limitations during early- and late-waterlogging, which also impacted shoot and root growth. Early-waterlogged plants of both barley and rapeseed were able to recover in growth upon drainage, and seed production reached ca. 79–85% of the controls, while late-waterlogged plants only attained 26–32% in seed production. Field pea showed no ability to develop root aerenchyma when waterlogged, and its photosynthesis (and stomatal and mesophyll conductances) was rapidly decreased by the stress. Consequently, waterlogging drastically reduced field pea seed production to 6% of controls both at early- and late-stages with plants being unable to resume growth upon drainage. In conclusion, wheat generates a set of adaptive responses to withstand 14 days of waterlogging, barley and rapeseed can still produce significant yield if transiently waterlogged during early plant stages but are more adversely impacted at the late stage, and field pea is not suitable for areas prone to waterlogging events of 14 days at either growth stage

Functional convergence of growth responses to shade and warmth in Arabidopsis

Shade and warmth promote the growth of the stem, but the degree of mechanistic convergence and functional association between these responses is not clear. We analysed the quantitative impact of mutations and natural genetic variation on the hypocotyl growth responses of Arabidopsis thaliana to shade and warmth, the relationship between the abundance of PHYTOCHROME INTERACTING FACTOR 4 (PIF4) and growth stimulation by shade or warmth, the effects of both cues on the transcriptome and the consequences of warm temperature on carbon balance. Growth responses to shade and warmth showed strong genetic linkage and similar dependence on PIF4 levels. Temperature increased growth and phototropism even within a range where damage by extreme high temperatures is unlikely to occur in nature. Both cues enhanced the expression of growth-related genes and reduced the expression of photosynthetic genes. However, only warmth enhanced the expression of genes involved in responses to heat. Warm temperatures substantially increased the amount of light required to compensate for the daily carbon dioxide balance. We propose that the main ecological function of hypocotyl growth responses to warmth is to increase the access of shaded photosynthetic organs to light, which implies functional convergence with shade avoidance.Fil: Romero Montepaone, Sofía Iara. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Sellaro, Romina Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Hernando, Carlos Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Costigliolo Rojas, María Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Bianchimano, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Ploschuk, Edmundo Leonardo. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cultivos Industriales; ArgentinaFil: Yanovsky, Marcelo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Casal, Jorge José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentin

Absorción de agua y rendimiento de maíz en campos bajos ¿Es el horizonte nátrico una limitante?

Los campos bajos son una de las últimas áreas de expansión de la frontera agrícola en nuestro país. Un ejemplo es la Cuenca del Salado, que es una región que en la última década mostró incrementos de la superficie sembrada con cultivos agrícolas. Este trabajo, investigó los patrones de absorción de agua del cultivo de maíz en suelos Natracuoles, bajo dos regímenes hídricos contrastantes. Se realizaron mediciones semanales de humedad gravimétrica y se comparó la evolución del agua disponible para el cultivo a lo largo del ciclo. El rendimiento y la biomasa total disminuyeron ante incrementos del PSI, el pH y la CE. El régimen hídrico no redujo los niveles de producción (8260 a 8872 kg ha-1). El horizonte A, alcanzó aportes de hasta 90% del agua disponible, mientras que el horizonte Bt solo aportó el 50%. Este horizonte, redujo 141 kg ha-1 los rendimientos de maíz por cada unidad de sodio intercambiable, pero no los limitó totalmente. Una parte del aporte hídrico al cultivo provino de capas más profundas del suelo, demostrando que el horizonte nátrico no limitó totalmente la profundidad efectiva del cultivo. Estos resultados abren nuevas perspectivas para el desarrollo de la agricultura en la región.Fil: Garello, F.J. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Cuenca del Salado. Agencia de Extensión Rural Chascomus; ArgentinaFil: Aguero, M.A. Universidad Nacional de La Plata; ArgentinaFil: Crespo, M. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Cicchino, M.A. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Cuenca del Salado. Agencia de Extensión Rural Chascomus; ArgentinaFil: Melani, Esteban. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Cuenca del Salado. Agencia de Extensión Rural Chascomus; ArgentinaFil: Ploschuk, Edmundo. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Cultivos Industriales; ArgentinaFil: Taboada, Miguel Angel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instuto de Suelos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Development of new perennial oil crops for marginal environments : productivity of Lesquerella mendocina under different nitrogen availability

Ploschuk, Edmundo Leonardo. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cultivos Industriales. Buenos Aires, Argentina.Windauer, Liliana Beatriz. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cultivos Industriales. Buenos Aires, Argentina.93-98Naturalized populations of Italian ryegrass (Lolium multiflorum Lam.) grow in different environments in Buenos Aires Province (Argentina). Juvenile plants of a cultivar and 20 populations collected in central-east areas of this Province were analysed in two environments with different soil types (Argiudol and Natracuol). At each site, 40 plants per plot were transplanted isolated, in a complete randomized blocks with three replicates. Morphological and agronomic traits were registered and ANOVA between environments were performed, with the replicates nested in the environments, and the genetic determination grade (GDG) was estimated. With the data registered during the trial as well as other previously obtained for the same populations, the affinity among populations was calculated by multivariate analysis. The genotype × environmental interaction resulted negative only for plant diameter and dry matter production as a result of the poor variation of the populations in the Natracuol soil type. Differences among populations and between environments in the majority of the characters were detected and the GDG was low to medium. The best performance was detected in Argiudol soil as a result of the limiting conditions of the Natracuol soil on the populations. Cluster analysis of the data in each environment showed differences in the affinity of the populations. The provenance of the most different populations was in the periphery of the area collected, while the ones distributed in the central area presented an affinity superior to 50%. Principal components analysis and the minimum spanning tree contributed to establish the affinity of the populations

Development of new perennial oil crops for marginal environments : productivity of Lesquerella mendocina under different nitrogen availability

Ploschuk, Edmundo Leonardo. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cultivos Industriales. Buenos Aires, Argentina.Windauer, Liliana Beatriz. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cultivos Industriales. Buenos Aires, Argentina.93-98Naturalized populations of Italian ryegrass (Lolium multiflorum Lam.) grow in different environments in Buenos Aires Province (Argentina). Juvenile plants of a cultivar and 20 populations collected in central-east areas of this Province were analysed in two environments with different soil types (Argiudol and Natracuol). At each site, 40 plants per plot were transplanted isolated, in a complete randomized blocks with three replicates. Morphological and agronomic traits were registered and ANOVA between environments were performed, with the replicates nested in the environments, and the genetic determination grade (GDG) was estimated. With the data registered during the trial as well as other previously obtained for the same populations, the affinity among populations was calculated by multivariate analysis. The genotype × environmental interaction resulted negative only for plant diameter and dry matter production as a result of the poor variation of the populations in the Natracuol soil type. Differences among populations and between environments in the majority of the characters were detected and the GDG was low to medium. The best performance was detected in Argiudol soil as a result of the limiting conditions of the Natracuol soil on the populations. Cluster analysis of the data in each environment showed differences in the affinity of the populations. The provenance of the most different populations was in the periphery of the area collected, while the ones distributed in the central area presented an affinity superior to 50%. Principal components analysis and the minimum spanning tree contributed to establish the affinity of the populations

Growth during recovery evidences the waterlogging tolerance of forage grasses

Waterlogging is a stress of increasing importance for pastures as a consequence of global climate change. We evaluated the impact of waterlogging on four forage grasses with alleged differential tolerance, emphasising not only responses during the stress but also their reported ability to recover from it. To do this, 42-day plants of Dactylis glomerata, Bromus catharticus, Festuca arundinacea and Phalaris aquatica were subjected to 15-day waterlogging, followed by a subsequent 15-day recovery period. Shoot and root growth (i.e. RGR) during both periods, in addition to net photosynthesis and stomatal conductance rates during waterlogging were assessed. Sensitivity exhibited by D. glomerata and B. catharticus during waterlogging was related to growth arrest of roots - but not of shoots - along with a progressive fall in stomatal conductance and net photosynthesis. The injury during waterlogging preceded a negligible growth of shoots and roots, only evident during recovery in both species. By contrast, P. aquatica exhibited unaltered root RGR and promoted shoot RGR with no impact on leaf gas exchange during waterlogging; whereas F. arundinacea showed intermediate tolerance as root RGR was reduced during waterlogging, with stomatal conductance, net photosynthesis and shoot RGR remaining unaffected. These latter two species fully regained shoot and root RGR during recovery. So, P. aquatica and F. arundinacea seem more suitable for prone-to-flood lowlands, whereas to be conclusive about waterlogging tolerance, it is necessary to examine plant recovery as shown in D. glomerata and B. catharticus.Fil: Ploschuk, Rocio Antonella. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Grimoldi, Agustin Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Ploschuk, Edmundo Leonardo. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Striker, Gustavo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. The University of Western Australia; Australi