Potencial bioindicador de samambaias epífitas em ambientes com diferentes graus de urbanização

Abstract

The intense growth of urbanization and industrialization has caused several changes in environmental conditions, directly affecting air quality. Among the substances responsible for air pollution, that caused by heavy metals has emerged as a problem in urban and rural environments. Bioindication and biomonitoring are favorable alternatives for assessing the impact of air pollution. The aim of this study was to evaluate the potential of Microgramma squamulosa (Kaulf.) de la Sota and Pleopeltis astrolepis (Liebm.) E.Fourn. (Polypodiaceae) as bioindicators and biomonitors of air pollution by heavy metals, by analyzing the concentration of these elements in the leaves, as well as in the substrate, and verifying whether the pollution promotes changes in leaf anatomy in these species in environments with different degrees of urbanization. The samples were collected at four points, being two urban green areas and two fragments of seasonal semideciduous forest in municipalities in the Southeast Region of Brazil. Leaves were analyzed for specific leaf area and leaf surface and cross-section parameters. An inductively coupled plasma optical emission spectrometer (ICP OES) was used to analyze the chemical elements Ag, Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni and Zn. In M. squamulosa there was a greater accumulation of Cr in the leaves collected in the environment closer to rural areas compared to the more anthropized environment. In P. astrolepis, a significant difference was found only in the element Ca, which had a higher concentration in the more urbanized environment. Furthermore, a negative correlation was also found between several anatomical characters and the Cu concentration in P. astrolepis. In both species there were alterations in the leaf tissues, highlighting the stomatal and leaf surface alterations. However, only in P. astrolepis significant changes were observed between environments with greater and lesser human intervention in the specific leaf area, in the thickness of chlorophyllian tissues and in the total thickness of the leaf. Therefore, responses to the environments were observed, with possible reactions not only to urban air pollution, but also to rural pollution.