Influência do ambiente urbano na estrutura anatômica de Schizolobium parahyba (Vell.) S. F. Blake (Leguminosae: Caesalpinioideae)

Abstract

The urbanization process has transformed the natural environment in an environment marked mainly by altered climatic conditions and high pollution. Knowledge of the effects of urbanization in the Atlantic Forest species is still incipient, due to the biological wealth of the biome. In this context, this study aims to evaluate the impact of urbanized environment in the leaf and wood structure of Schizolobium parahyba (Vell.) S. F. Blake, a native species of the Atlantic Rainforest. The study was conducted at two sites located in the city of Rio de Janeiro: a remnant of the Atlantic Rainforest - forest site; and a site located in one of the city's main traffic routes - urban site. To characterize the sites, climatic conditions and elemental analysis were performed. Soil and leaves elemental analysis were run by energy dispersive x-ray fluorescence technique (EDXRF). Samples of leaves and wood were processed according to standard techniques in plant anatomical studies for evaluate the structure. The urban site had a higher water deficit, lower nutrient concentrations and higher concentrations of potentially toxic chemicals to plants, such as zinc and lead, in soil. Leaves of plants of urban site had greater thickness of spongy parenchyma and higher concentrations of sulfur, chlorine, titanium, iron, zinc and bromine. The wood of trees of urban site had greater frequency and length of the vessel elements, clustering index greater and vulnerability, conductance and mesomorphy index smaller. The anatomical characters of leaf and analyzed wood showed low phenotypic plasticity in the studied conditions, considered with high plasticity only the characters: frequency trichomes in leaf and vessel elements in wood. We observed the influence of human activities on concentration and occurrence of chemical elements, through the performed analysis. Despite the low plasticity, the changes observed in leaf and wood of species suggest that this species is able to change their anatomical structure in order to increase their water security and take advantage of the available resources, as high concentration of atmospheric CO2. Thus, the results show that Schizolobium parahyba is tolerant species, capable to adapt itself to the urban environment