12 research outputs found
Plant Functional Groups Composition Associated to Management Practices in Temperate Natural Grasslands (Flooding Pampa, Argentina)
Seed bank Synamics of Paspalum quadrifarium Lam. in the Flooding Pampa
Paspaium quadrifarium, ("paja colorada”) puede ser considerada una maleza y un recurso forrajero valioso de los pastizales naturales de la Pampa Deprimida. Las quemas inverno-primaverales de las comunidades dominadas por esta especie ("pajonales”) posibilitan rápidos incrementos de su receptividad ganadera. A fin de contribuir al conocimiento de la demografía de esta especie, se analizó la dinámica del banco de cariopsis. llamadas "semillas" bajo distintas condiciones de fuego y pastoreo. Los resultados indican que: a) Las semillas de paja colorada carecen de mecanismos de dormición; b) El pastoreo sobre pajonales no quemados no afecta la producción de cariopsis de paja colorada; c) El fuego al actuar aisladamente o en combinación con pastoreo, redujo la producción de semillas durante el primer ciclo de crecimiento pos-quema. No obstante, durante el ciclo siguiente, se registró una respuesta compensatoria, en términos de proporción de semillas viables.Paspalum quadrifarium can be considerad a weed or an useful forage resource of the Flooding Pampa. When bumed during the winter-spring period, the communities dominated by this specles ("pajonales”) show fast increments in stocking capacity for cattle. To contribute at the demographic knowledge of Paspalum quadrifarium, the dynamics of the seed bank was studied under different conditions of buming and grazing. The results suggesit that: a) Paspalum quadrifarium fiack dormition mechanisms; b) grazing didn’t affect seed ipmductlon; c) buming foilowed by grazing or buming wjthout grazing, ireduce ¡seed production during the first post-bum growing cyde. However, during the following eyeie, a compensatory responso of viable seeds was found since they had an increase.Universidad Nacional de La Plata (UNLP) - Facultad de Ciencias Agrarias y Forestale
Seed bank Synamics of Paspalum quadrifarium Lam. in the Flooding Pampa
Paspaium quadrifarium, ("paja colorada”) puede ser considerada una maleza y un recurso forrajero valioso de los pastizales naturales de la Pampa Deprimida. Las quemas inverno-primaverales de las comunidades dominadas por esta especie ("pajonales”) posibilitan rápidos incrementos de su receptividad ganadera. A fin de contribuir al conocimiento de la demografía de esta especie, se analizó la dinámica del banco de cariopsis. llamadas "semillas" bajo distintas condiciones de fuego y pastoreo. Los resultados indican que: a) Las semillas de paja colorada carecen de mecanismos de dormición; b) El pastoreo sobre pajonales no quemados no afecta la producción de cariopsis de paja colorada; c) El fuego al actuar aisladamente o en combinación con pastoreo, redujo la producción de semillas durante el primer ciclo de crecimiento pos-quema. No obstante, durante el ciclo siguiente, se registró una respuesta compensatoria, en términos de proporción de semillas viables.Paspalum quadrifarium can be considerad a weed or an useful forage resource of the Flooding Pampa. When bumed during the winter-spring period, the communities dominated by this specles ("pajonales”) show fast increments in stocking capacity for cattle. To contribute at the demographic knowledge of Paspalum quadrifarium, the dynamics of the seed bank was studied under different conditions of buming and grazing. The results suggesit that: a) Paspalum quadrifarium fiack dormition mechanisms; b) grazing didn’t affect seed ipmductlon; c) buming foilowed by grazing or buming wjthout grazing, ireduce ¡seed production during the first post-bum growing cyde. However, during the following eyeie, a compensatory responso of viable seeds was found since they had an increase.Universidad Nacional de La Plata (UNLP) - Facultad de Ciencias Agrarias y Forestale
Emergence and initial growth of tall fescue free and infected with wild or safe endophytes
El objetivo de este trabajo fue evaluar, durante la etapa temprana de implantación de festuca alta, el porcentaje y la velocidad de emergencia, la producción de biomasa y la proporción de raíz en plantas provenientes de una población naturalizada del sudeste de la Provincia de Buenos Aires (S) y del cv. Taita (T), libres (S- y T-, respectivamente) e infectadas con el endófito silvestre Epichloë coenophiala (S+) y con el endófito seguro AR584 (T+) respectivamente. Se sembraron ocho bandejas plantineras de 50 celdas para cada tratamiento (i.e. S-, S+, T- y T+) y se ubicaron de forma tal que la superficie superior de la misma quedara al ras del suelo en una parcela preparada para la siembra de una pastura. El número de plántulas emergidas en cada bandeja se registró diariamente hasta los 28 días desde la siembra y se determinó el porcentaje y la velocidad de emergencia. A los 47 días desde la siembra se determinó la materia seca de la parte aérea y radical de las plantas emergidas. A los 28 días desde la siembra, no se registraron diferencias significativas en el número de plantúlas emergidas dentro de las festucas infectadas (p=0,9965) ni entre las libres (p=0,7525). No se encontraron diferencias significativas (p=0,4738) entre las festucas en la velocidad de emergencia. Las festucas infectadas presentaron una biomasa total por planta superior a la de las libres debido a una mayor biomasa de raíces, aunque las diferencias para ambas variables sólo fueron significativas (p<0,001) en el caso del cv. Taita. En nuestras condiciones la presencia del endófito aumentó el porcentaje de plántulas emergidas tanto en la población naturalizada como en Taita, y promovió el desarrollo radical en este último.The objective of this work was to assess, during the early stages of tall fescue implantation, the percentage of emergence, the emergence speed index, biomass production and root proportion of a naturalized population from Buenos Aires province (S) and cv. Taita (T), free (S- and T-, respectively) and infected with the wild endophyte Epichloë coenophiala (S+) and with the safe endophyte AR584 respectively (T+). Eight seedling trays with 50 cells were sown for each treatment (i.e. S-, S+, T- and T+) and placed on a bare soil in such a way that the upper surface of the trays was at soil level. The number of emerged seedlings was recorded daily up to 28 days after sowing and percentage and emergence speed index were calculated. At 47 days from sowing the biomass of shoot and roots of the plants was determined. At 28 days from sowing, no significant differences were registered in the number of emerged seedlings within endophyte-infected (p=0.9965) or endophyte-free (p=0.7525) treatments. No significant differences (p=0.4738) were found among treatments for the emergence speed index. The total biomass per plant for endophyte-infected tall fescues was higher than for endophyte-free ones due to a higher root biomass, although for both variables the differences were significant (p<0,001) only in cv. Taita. In our conditions, the presence of both endophytes allowed the respective tall fescues to increase the percentage of seedling emergence and to promote root development in cv. Taita.Facultad de Ciencias Agrarias y Forestale
Flooding tolerance in five populations of Lotus glaber Mill. (Syn. Lotus tenuis Waldst. et. Kit.)
Biomass allocation to vegetative and reproductive organs in Lotus glaber and L. corniculatus (Fabaceae)
Reproductive Development of Lotus tenuis (Fabaceae) Crop Defoliated at Different Times and Intensities
Abstract Lotus tenuis forage yield has been quantified under defoliation conditions in pastures, grasslands and under dual-purpose production of both livestock forage and seeds. However, little is known about the effects of defoliation management on L. tenuis flower and pod production and subsequent seed yield. Two field experiments were conducted to study the response of L. tenuis to defoliation at different flowering stages and intensities. In Experiment 1, crops were defoliated at the beginning of the flowering (DBF), mid-flowering (DMF) or full flowering (DFF). In Experiment 2, defoliation was in vegetative stage at low (LDI) or high (HDI) intensities. Defoliation in Experiment 1 neither affected plant cover nor the photosynthetically active radiation intercepted by the crop during pod production. There were less umbels with dehiscent (shattered) pods in the DFF treatment than in Control, DBF and DMF treatments. Flower peak occurred first in the Control, DBF and DMF treatments, and eight days later in DFF plots, however, seed yield was not affected (1324 ± 32.8 kg·ha −1 ). Defoliation intensity did not affect seed yield (962 ± 25.9 kg•ha − 1 ) because of self-compensation which increased harvest index in HDI (14.5% ± 0.6%) compared to the Control and LDI (12.0% ± 0.3%) treatments. Plant survival was not affected by defoliation treatments in any of the experiments. Flowering can be synchronized through defoliation. The blooming of large numbers of flowers in a short time was achieved, reducing the number of shattered pods. Compensatory responses through plant plasticity conferred L. tenuis the ability to overcome defoliation without affecting seed yield. Lotus tenuis defoliation as management tool will be considered in future researches because it is possible to harvest forage and to increase seed yield through a reduction of shattered pods. O. R. Vignolio et al
Fire management of tall tussock grasslands in the flooding Pampa of Argentine.
[email protected] analítica--semestra
Tolerance to flooding in five Brachiaria brizantha accessions Tolerância ao alagamento em cinco acessos de Brachiaria brizantha
Some physiological and morphological responses of five Brachiaria brizantha accessions (BRA000591 cultivar Marandu, BRA003441, BRA002844, BRA004308 and BRA004391) were compared for plants grown in pots under flooding and well-drained conditions for 14 days. Flooding caused a significant reduction in leaf dry mass production in all accessions, but, for root biomass, no differences between treatments could be detected in BRA003441 and BRA004391. No adventitious root production was observed in flooded BRA003441; all other accessions produced adventitious roots when flooded. Relative growth rate was reduced by flooding only in BRA000591 and BRA004308. Leaf elongation rate was reduced by flooding in all accessions, however, more severely in BRA003441. Net photosynthesis was reduced by flooding in all accessions, but with less intensity in BRA004391. For all accessions, there was a close relationship between net photosynthesis and stomatal conductance under flooding. The five accessions tested differed in tolerance to flooding. BRA004391 was the most tolerant. Accession BRA003441 was the most sensitive, followed by BRA000591 cultivar Marandu. Accessions BRA002844 and BRA004308 were classified as intermediate in flooding tolerance.<br>Algumas respostas morfológicas e fisiológicas de cinco acessos de Brachiaria brizantha (BRA000591 cultivar Marandu, BRA003441, BRA002844, BRA004308 e BRA004391) foram comparadas em plantas cultivadas em vasos, sob condições de solo alagado e bem drenado, durante 14 dias. O alagamento reduziu significativamente a produção de massa seca foliar em todos os acessos, mas para a massa seca radicular, não foi possível encontrar diferenças entre tratamentos em BRA003441 e BRA004391. Somente BRA003441 não produziu raízes adventícias sob alagamento. A taxa de crescimento relativo foi reduzida pelo alagamento somente em BRA000591 e BRA004308. A taxa de elongação foliar foi reduzida pelo alagamento do solo em todos os acessos, porém, com maior severidade em BRA003441. O alagamento reduziu a fotossíntese líquida em todos os acessos, porém, menos intensamente em BRA004391. Em todos os acessos encontrouse uma estreita relação entre as taxas de fotossíntese líquida e a condutância estomática sob alagamento. Os cinco acessos testados diferiram na sua tolerância relativa ao alagamento do solo. BRA004391 foi o mais tolerante. O acesso BRA003441 foi o menos tolerante, seguido por BRA000591 cultivar Marandu. Os acessos BRA002844 e BRA004308 foram considerados como intermediários em tolerância ao alagamento do solo
Arbuscular mycorrhizal symbiosis in salt-tolerance species and halophytes growing in salt-affected soils of South America
Arbuscular mycorrhizal fungi (AMF) are ubiquitous soil microorganisms that establish a direct physical link between soil and plant roots constituting an integral component of the natural ecosystems being present in saline environment. These fungi are associated with the roots of over 80% terrestrial plant species including halophytes. Compared with other parts of the world, published information on halophytes vegetation adapted to saline environments in South America, and even more so on their utilization, is quite scarce. This work showed the mycorrhizal status of halophytes and salt-tolerance species capable of growing in salty soils, used as a forage resource for livestock. Specially we made a focus in two saline soils of Argentinean Pampas and Salinas Grandes dominated by Lotus tenuis and members of Chenopodiaceae family respectively. This data is of relevance because they often constitute the only forage resource for the possible way to utilize these plants to remediate salt-affected soils.Fil: Becerra, Alejandra Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Cofré, María Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: García, Ileana Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin