Expansión de la agricultura : la tragedia del éxito

Fil: Ghers, Claudio M. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaEl éxito económico-social de las nuevas tecnologías, fundamentalmente aplicadas al\ncultivo de soja, creó una expansión epidémica con consecuencias trágicas que resultan\nen transformaciones donde la homogenización y los efectos masivos de acumulación y\ndominio se hacen evidentes

Ozone Exposure of a Weed Community Produces Adaptive Changes in Seed Populations of Spergula arvensis

Tropospheric ozone is one of the major drivers of global change. This stress factor alters plant growth and development. Ozone could act as a selection pressure on species communities composition, but also on population genetic background, thus affecting life history traits. Our objective was to evaluate the consequences of prolonged ozone exposure of a weed community on phenotypic traits of Spergula arvensis linked to persistence. Specifically, we predicted that the selection pressure exerted by high ozone concentrations as well as the concomitant changes in the weed community would drive population adaptive changes which will be reflected on seed germination, dormancy and longevity. In order to test seed viability and dormancy level, we conducted germination experiments for which we used seeds produced by S. arvensis plants grown within a weed community exposed to three ozone treatments during four years (0, 90 and 120 ppb). We also performed a soil seed bank experiment to test seed longevity with seeds coming from both the four-year ozone exposure experiment and from a short-term treatment conducted at ambient and added ozone concentrations. We found that prolonged ozone exposure produced changes in seed germination, dormancy and longevity, resulting in three S. arvensis populations. Seeds from the 90 ppb ozone selection treatment had the highest level of germination when stored at 75% RH and 25 °C and then scarified. These seeds showed the lowest dormancy level when being subjected to 5 ºC/5% RH and 25 ºC/75% followed by 5% RH storage conditions. Furthermore, ozone exposure increased seed persistence in the soil through a maternal effect. Given that tropospheric ozone is an important pollutant in rural areas, changes in seed traits due to ozone exposure could increase weed persistence in fields, thus affecting weed-crop interactions, which could ultimately reduce crop production.Fil: Landesmann, Jennifer Brenda. Consejo Nacional de Invest.cientif.y Tecnicas. Centro Cientifico Tecnol.conicet - Patagonia Norte. Instituto de Invest.en Biodiversidad y Medioambiente;Fil: Gundel, Pedro Emilio. Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Pque. Centenario. Instituto D/inv.fisiologicas y Eco.vinculadas A L/agric;Fil: Martinez Ghersa, M. Alejandra. Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Pque. Centenario. Instituto D/inv.fisiologicas y Eco.vinculadas A L/agric;Fil: Ghersa, Claudio Marco. Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Pque. Centenario. Instituto D/inv.fisiologicas y Eco.vinculadas A L/agric

Occurrence of Alkaloids in Grass Seeds Symbiotic With Vertically-Transmitted \u3cem\u3eEpichloë\u3c/em\u3e Fungal Endophytes and Its Relationship With Antioxidants

Host organisms can acquire new functional traits through symbiosis. Seed-transmitted Epichloë fungal endophytes are known to protect host plants against herbivores and increase tolerance to abiotic stresses by alkaloids and antioxidants, respectively (currencies of mutualism). Whereas, alkaloids are fungal products with demonstrated effects at plant vegetative stage, few studies have focused on alkaloids in seeds. We assessed the occurrence of fungal alkaloids and determined their concentrations in seeds of two host grasses, Festuca rubra and Lolium multiflorum. Then, we sought for a relationship with the antioxidants tocochromanols and glutathione, which are involved in the control of oxidative stress. Different alkaloids were detected depending on the species and plant genotype. Most notably, loline alkaloids were not detected in F. rubra seeds, whereas ergovaline and peramine were absent in L. multiflorum. In F. rubra, ergovaline concentration was dependent on the maternal line in interaction with the production year, diminishing in seeds after 1 year of storage. The exposure of L. multiflorum plants to ozone had no effect on the seed concentration of lolines. There was a significant positive relationship between the concentrations of ergovaline and tocochromanols in both species, and between ergovaline concentration and EGSSG/2GSH (glutathione half-cell reduction potential) in RAB maternal line of F. rubra. These results suggest that alkaloid and antioxidants have a close association in seeds of host grasses, and that the alkaloid bioactivity could be related with the antioxidant capacity to control stress. This has important implications for the ecology of partner species, thus supporting its consideration for further research

Occurrence of Alkaloids in Grass Seeds Symbiotic With Vertically-Transmitted Epichloë Fungal Endophytes and Its Relationship With Antioxidants

Host organisms can acquire new functional traits through symbiosis. Seed-transmitted Epichloë fungal endophytes are known to protect host plants against herbivores and increase tolerance to abiotic stresses by alkaloids and antioxidants, respectively (currencies of mutualism). Whereas, alkaloids are fungal products with demonstrated effects at plant vegetative stage, few studies have focused on alkaloids in seeds. We assessed the occurrence of fungal alkaloids and determined their concentrations in seeds of two host grasses, Festuca rubra and Lolium multiflorum. Then, we sought for a relationship with the antioxidants tocochromanols and glutathione, which are involved in the control of oxidative stress. Different alkaloids were detected depending on the species and plant genotype. Most notably, loline alkaloids were not detected in F. rubra seeds, whereas ergovaline and peramine were absent in L. multiflorum. In F. rubra, ergovaline concentration was dependent on the maternal line in interaction with the production year, diminishing in seeds after 1 year of storage. The exposure of L. multiflorum plants to ozone had no effect on the seed concentration of lolines. There was a significant positive relationship between the concentrations of ergovaline and tocochromanols in both species, and between ergovaline concentration and EGSSG/2GSH (glutathione half-cell reduction potential) in RAB maternal line of F. rubra. These results suggest that alkaloid and antioxidants have a close association in seeds of host grasses, and that the alkaloid bioactivity could be related with the antioxidant capacity to control stress. This has important implications for the ecology of partner species, thus supporting its consideration for further research

Diseños de emergencia y supervivencia de las plantas de sorgo de Alepo, menores de un año en cultivos de invierno

p.85-91Se estudio el diseño de emergencia y supervivencia de plantas de sorgo de Alepo menores de un año en experimentos conducidos a campo con diferentes sistemas de cultivos de invierno. Se analizaron tres sistemas (cultivo de trigo, avena y área sin cultivo) en el área de Rojas, Pcia. de Buenos Aires, durante 1981 y un sistema (cultivo de trigo) en Luján, Pcia. de Buenos Aires, durante 1982. Los diseños de aparición de plántulas fueron similares en los sistemas de Rojas y Luján. Se observó un primer flujo de emergencia, concentrado en un período no mayor de treinta días, cuya contribución relativa al número total de plántulas producidas fue del 76 por ciento en el promedio de todos los sistemas. Según el sistema considerado, la emergencia posterior de plántulas se produjo en uno o más flujos de cuantitativamente menor importancia. Se observaron diferencias entre los sistemas cultivados durante 1981 y 1982, tanto en el momento del comienzo de la emergencia de las plántulas como en los modelos de supervivencia obtenidos. El primer flujo de aparición de plántulas se produjo en 1982, 35 días antes que en 1981. Asimismo, en 1981, al final del ciclo del cultivo, sólo el 30 por ciento de las plántulas provenientes del primer flujo, en promedio, habían sobrevivido, en tanto que el 80 por ciento lo hizo en 1982. Se discuten los resultados en relación con su importancia sobre la dinámica poblacional de la maleza

Germination (%) of <i>Spergula</i><i>arvensis</i> seeds for each ozone selection treatment, pre-treatment and incubation temperature.

<p>White, grey and black bars represent germination of seeds (n = 3, ± SE) for 0, 90 and 120 ppb ozone selection treatment, respectively, after 22 days of exposure to pre-treatments: storage at 10 °C and dry condition (control) (A), storage at 5 °C and 75% RH followed by scarification (B), and storage at 25 °C and 75% followed by scarification (C); and then incubated at 10, 15 and 15/25 °C. Above each plot, <i>P-values</i> indicate the effects of Incubation Temperature (Temp.), Ozone selection treatment (Ozone) and the interaction (Temp. xOzone) within each Pre-treatment.</p