Conteúdo de Tococromanóis em espécies arbóreas de várzea da Amazônia Central sob condições controladas

With more than 1,000 registered tree species, Amazonian white-water (várzea) forests are the most species-rich floodplain forests worldwide. The floodplain vegetation colonizing such environments is subjected to a gradient of different levels of inundation, which define habitats from permanently aquatic, at the lowest positions, to almost terrestrial at higher positions. Annual flooding in these forests may reach the height of 15 m, although its mean amplitude is of 10 m, which corresponds to an inundation period of trees of up to 270 days per year. The present study investigated the content of E Vitamins in leaves of 19 common tree species of Amazonian várzea in order to test for the relation between the antioxidant properties of E Vitamins and the occurrence of tree species along the flooding gradient. Three evergreen species were selected to perform experiments in climatic chambers, Garcinia brasiliensis, Laetia corymbulosa and Pouteria glomerata, under the following experimental conditions: 1) gradual artificial inundation associated with light suppression, 2) darkness, and 3) drought (relative humidity = 45% ± 5%); all of them over a 120 days period. Investigated parameters were: the content of tococromanols, chlorophyll fluorescence, leaf anatomy, and flushing and shedding of leaves. The results show that the α-tocoferol concentration relates primarily to the growth rate of the species rather than their position at the flooding gradient in the natural environment. The latex of G. brasiliensis presented 7 of the 8 existing forms of E vitamins. Plants subjected to drought and plants that were located in the greenhouse showed the highest concentrations of α-tocoferol. G. brasiliensis was characterized through very high δ-tocotrienol concentrations, constituting the second record ever described in literature pointing out the occurrence of this E-vitamin in plant leaves. The Fv/Fm ratio of chlorophyll fluorescence never declined below the threshold of 0,5. When the Fv/Fm ratio of the species subjected to drought approached to values slightly below 0,6, the species shed their leaves. After 120 days of flooding, leaf anatomy of individuals of all the investigated species was different from that of individuals located in the greenhouse. From all potencially stressful conditions, drought demonstrated the highest impact, while under artificial inundation plants were highly tolerant, keeping their leaves all over the experimental period. Although using different strategies, the three tested species survived the potentially stressful conditions without major problems, recovering themselves efficiently after suppressing the experimental conditions.Com mais de 1.000 espécies arbóreas registradas, as florestas de várzea são as florestas inundáveis mais diversas do mundo. A vegetação inundável que coloniza estes ambientes está inserida em um gradiente de diferentes níveis de inundação, que definem habitats desde permanentemente aquáticos, nas cotas mais baixas, até totalmente terrestres, nas cotas mais altas. Nestas áreas, a inundação anual média é de 10 m, entretanto, pode alcançar até 15 m de altura, o que, conforme a altura de relevo considerada, corresponde a um tempo de inundação que chega a 270 dias por ano. No presente estudo foi realizado um Screening de vitamina E para 19 espécies arbóreas de várzea, de modo a relacionar o poder antioxidante da vitamina E à posição topográfica ocupada pelas plantas no ambiente natural. Três espécies Perenifólias foram escolhidas para experimento em condições controladas em câmaras climáticas: Garcinia brasiliensis, Laetia corymbulosa e Pouteria glomerata. As condições experimentais foram: 1) inundação artificial gradativa associada à supressão de luz por 120 dias, 2) escuro por 120 dias e 3) seca (umidade relativa de 45% ± 5%). Os parâmetros investigados foram: o conteúdo de tococromanóis, a fluorescência de clorofila a, a anatomia foliar e a manutenção, a perda e a produção de folhas. Os resultados mostraram que o reservatório de α-tocoferol está mais relacionado à taxa de crescimento das espécies do que à posição das plantas no gradiente de inundação em ambiente natural. O látex de G. brasiliensis possui 7 das 8 formas de vitamina E existentes. No experimento de câmaras climáticas, as maiores taxas de α-tocoferol encontradas foram nas plantas do tratamento seca e da casa de vegetação. A espécie G. brasiliensis mostrou grande conteúdo de δ-tocotrienol, sendo este o segundo registro deste composto ocorrendo naturalmente em folhas. A razão Fv/Fm da fluorescência de clorofila a em nenhum dos tratamentos decresceu abaixo de 0,5. As plantas do tratamento seca ao atingirem valores um pouco abaixo de 0,6 perderam suas folhas. A anatomia das folhas das três espécies mostrou diferenças quando comparadas plantas inundadas por 120 dias com plantas de casa de vegetação. A seca se mostrou, para os parâmetros analisados, o tratamento de maior impacto sobre as plantas, enquanto que sob inundação artificial as plantas se mostraram altamente tolerantes, mantendo as folhas durante todo o experimento. Em todas as situações potencialmente estressantes, testadas para as três espécies, as plantas mesmo mostrando estratégias distintas, conseguiram sobreviver e mostraram rapidez de recuperação ao sair das condições experimentais impostas

Germination in four low-várzea tree species of Central Amazonia

Trees of Central Amazonian white-water (várzea) forests are highly adapted to the annual inundations, which can last up to 7 months every year. Many trees synchronize fruit production to the period of highest water levels of the rivers, and hydrochory is especially common in species that colonize the low-lying flood-levels flooded for longer periods. The effect of the contact of diaspores with the river water is controversially discussed in literature. While many studies describe that flooding breaks the dormancy in seeds of many várzea tree species and is necessary for germination, other studies mention that seed buoyancy and/or submergence have negative effects on germination. Therefore, the present study was designed in order to test experimentally how seed buoyancy and seed submergence affect germination in four várzea tree species of the low-lying flood-levels. The tested species with buoyant seeds were Salix martiana and Pseudobombax munguba, those with submerged seeds Laetia corymbulosa and Vitex cymosa. 50 seeds from each species were (a) placed in water during a period of 15 days and afterwards moved to várzea substrate, thus simulating seed buoyancy and/or submergence in the natural environment, and (b) directly placed in várzea substrate, with four repetitions, respectively. Three species showed significantly higher percentages of germination in the flooded seeds than in the non-waterlogged seeds, while fruit-fibre involved seeds of P. munguba showed an opposite trend. In L. corymbulosa, germination initiated earlier in the submerged than in the control seeds, whereas there was no difference in the start of germination between waterlogged and non-waterlogged seeds of the other species. From buoyant seeds of P. munguba and S. martiana, seedlings with entirely formed cotyledons were developed while still in water. These seedlings were characterized by morphological differences in comparison to seedlings originating from non-waterlogged seeds and could not protrude the root into the soil (i.e. establish) when placed in the substrate. It is likely that the seed involving fruit-fibres contribute to long-distance dispersal in these species in the natural environment, and to stabilize seedlings when diaspores land on substrate. Concluding, contact with the river water did not disturb but on the contrary enhanced germination in the four studied species. © 2006 Elsevier B.V. All rights reserved

Implementation of the Ramsar Convention on South American wetlands: an update

Made available in DSpace on 2016-02-26T21:28:32Z (GMT). No. of bitstreams: 5 implementation.pdf: 1374807 bytes, checksum: 14321e691a49bc84c5f8d8e30a8b3b6d (MD5) license_url: 49 bytes, checksum: 4afdbb8c545fd630ea7db775da747b2f (MD5) license_text: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) license.txt: 120 bytes, checksum: c5ec8a89f6203da160ca192812b3f657 (MD5) Previous issue date: 2015This review presents the current knowledge regarding South American wetlands and summarizes major outcomes of the implementation of the Ramsar Convention on Wetlands of International Importance for the South American continent. South America is the wettest continent on Earth, with wetlands accounting for ~20% of its area. Wetlands harbor an exceptional rich biodiversity also including many endemic plant and animal species. They provide numerous ecosystem services in terms of provisioning material goods, regulating biogeochemical cycles, providing habitat, sustaining cultural practices, and importantly, contributing to the maintenance and generation of regional biodiversity. Major threats to wetlands include agroindustrial expansion, deforestation, soil erosion, mining, pollution, inadequate resource use, and large infrastructural projects such as reservoir construction for hydropower. South American countries were slow in adopting definitions, delineations, and classifications of their wetlands and in inventorying wetlands according to their extent and ecological characteristics. However, Ramsar sites are increasing continuously in both numbers and extent, covering 113 sites, totaling an area of ~373,000 km2. Threats to wetlands and Ramsar sites are ongoing, mainly because of the lack of specific national wetland policies, limited financial and human resources, general lack of infrastructure, and limited monitoring capacity. The process of changing perceptions on the value of wetlands and their ecosystem services is improving, but it could be hastened by improved infrastructure and cooperation between Ramsar sites, wetland scientists, and local stakeholders. Outreach to raise awareness of societies, administrators, and governments of the critical importance of wetlands continues to be a major challenge for the conservation of South American wetlands.

Implementation of the Ramsar Convention on South American wetlands: an update

This review presents the current knowledge regarding South American wetlands and summarizes major outcomes of the implementation of the Ramsar Convention on Wetlands of International Importance for the South American continent. South America is the wettest continent on Earth, with wetlands accounting for ~20% of its area. Wetlands harbor an exceptional rich biodiversity also including many endemic plant and animal species. They provide numerous ecosystem services in terms of provisioning material goods, regulating biogeochemical cycles, providing habitat, sustaining cultural practices, and importantly, contributing to the maintenance and generation of regional biodiversity. Major threats to wetlands include agroindustrial expansion, deforestation, soil erosion, mining, pollution, inadequate resource use, and large infrastructural projects such as reservoir construction for hydropower. South American countries were slow in adopting definitions, delineations, and classifications of their wetlands and in inventorying wetlands according to their extent and ecological characteristics. However, Ramsar sites are increasing continuously in both numbers and extent, covering 113 sites, totaling an area of ~373,000 km2. Threats to wetlands and Ramsar sites are ongoing, mainly because of the lack of specific national wetland policies, limited financial and human resources, general lack of infrastructure, and limited monitoring capacity. The process of changing perceptions on the value of wetlands and their ecosystem services is improving, but it could be hastened by improved infrastructure and cooperation between Ramsar sites, wetland scientists, and local stakeholders. Outreach to raise awareness of societies, administrators, and governments of the critical importance of wetlands continues to be a major challenge for the conservation of South American wetlands

Open access -Review Plant reproduction in the Central Amazonian floodplains: challenges and adaptations

Abstract Background The Central Amazonian floodplain forests are subjected to extended periods of flooding and to flooding amplitudes of 10 m or more. The predictability, the length of the flood pulse, the abrupt transition in the environmental conditions along topographic gradients on the banks of major rivers in Central Amazonia, and the powerful water and sediment dynamics impose a strong selective pressure on plant reproduction systems

Plant reproduction in the Central Amazonian floodplains : challenges and adaptations

The Central Amazonian floodplain forests are subjected to extended periods of flooding and to flooding amplitudes of 10 m or more. The predictability, the length of the flood pulse, the abrupt transition in the environmental conditions along topographic gradients on the banks of major rivers in Central Amazonia, and the powerful water and sediment dynamics impose a strong selective pressure on plant reproduction systems. In this review, we examine how the hydrological cycle influences the strategies of sexual and asexual reproduction in herbaceous and woody plants. These are of fundamental importance for the completion of the life cycle. Possible constraints to seed germination, seedling establishment and formation of seed banks are also covered. Likewise, we also discuss the importance of river connectivity for species propagation and persistence in floodplains. The propagation and establishment strategies employed by the highly diversified assortment of different plant life forms result in contrasting successional stages and a zonation of plant assemblages along the flood-level gradient, whose species composition and successional status are continuously changing not only temporally but also spatially along the river channel