Caracterização das estratégias ecofisiológicas de samambaias em resposta à inundação na restinga de Maricá, Rio de Janeiro, Brasil

Abstract

The flooded forests and swamps present in sandy coastal plains (restingas) triggere a series of processes influencing the physico-chemical and biological soil, bringing the plants make mechanisms of acclimation or adaptation to the stress of flooding as morphological and physiological changes in order to minimize the effects lack of oxygen. The most widely distributed species in restingas wetland environments are Acrostichum danaeifolium Langsd. & Fisch., Blechnum serrulatum Rich. and Thelypteris interrupta (Willd.) K. Iwats. The aim of this study is characterize the ecophysiological aspects of these ferns sporophytes have to survive in wetland environments at Restinga de Maricá, Rio de Janeiro state, Brazil. In the ferns sites was determined the physical and chemical soil characterization, leaf variation (thickness, density, mass per unit leaf, chlorophylls and quantitative attributes of epidermal cells) and the concentration of soluble carbohydrates and starch. The sampled of plants were collected in the rainy and dry station and the soil only dry station. The sites examined were extremely acid soils of low fertility and toxicity by macro and micro nutrients indicating that the ferns have tolerance to these factors. In the wet season (flood), the ferns showed a decline in foliage density, accompanied by an increase in mass per unit leaf. This ability to achieve dry weight gain per area classifies all ferns analyzed as flood tolerant. The high values of soluble carbohydrates in leaves indicate increased degradation of leaf starch. The lower contents of soluble carbohydrate found in the stems explains the reduction in respiration of plant roots under anoxia / hypoxia, to avoid oxidation and increased the stock of starch reserve elucidating strategy of tolerance to flooding. Reduced availability of water in the dry season directly affects leaf traits decreasing the stomata index, succulence and leaf mass per unit, in which reflects on the decline in chlorophyll concentrations. The lowest values of chlorophyll concentrations have a direct bearing on the leaf starches that are stored in the leaves and thus altering the dynamics of the carbohydrates in these species. The analysis of site where it grows Acrostichum danaeifolium indicates critical levels of Na in the soil, probably, to the production of mucilage in stems and petioles is a strategy of tolerance to saline and flooded environment. The high rate of coverage of Blechnum serrulatum in flooded environments indicates that the species has adapted to hydromorphic soils, including a large storage capacity of starch in the stem. The high sinuosity of epidermal cells in Thelypteris interrupta allows high succulence maintaining the hydrological status of the leaves in both seasons. These results add information about the neotropical ferns biology and they contribute to understanding the dynamics of occupation of herbaceous species in wetland environments in Brazilian restingas.