Diversidade vegetal, anatomia e histoquímica de plantas tóxicas ocorrentes em praças de Altamira-PA

Abstract

Toxic plants are organisms that possess chemical compounds that can cause alterations in living beings. Analysis of leaf anatomy and histochemistry of species like these are essential to understand their morphology and composition, in addition to assisting in the selection of species for urban vegetation with the planting of safe vegetation in public spaces, they are also essential for the prevention of intoxications. Therefore, the general objective of this research was to identify and describe the leaf anatomy and histochemistry of toxic species found in public squares in the city of Altamira-PA, with the aim of providing subsidies for the use in urban tree planting in the city, contributing to public health, environment, and safety of the population. For the study, the species present in 18 city squares were cataloged, with the help of an inventory guide that included photographic records, botanical e information and the use of GPS for the acquisition of geographical coordinates. The species were identified according to the APG IV System and through searches on specialized botanical databases. Subsequently, they were categorized and organized into spreadsheets totaling 122 species inventoried, of which, for this study, 35 toxic species were found, totaling 506 individuals. Among the results, Dracaena trifasciata (Prain) stood out with the highest density of individuals, representing 17.2% (87 individuals) of the total, belonging to the Asparagaceae family. This family, as well as Araceae and Euphorbiaceae, presented the highest number of toxic species, with five species each. The species with the highest frequency was Mangifera indica L., present in 61.1% of the squares. It is a toxic plant that can cause dermatitis by contact with the leaves and intoxication when the fruit skin is ingested. Independência Square presented the highest number of species, with 18 toxic plants. For leaf anatomy and histochemistry analyses, five of the most frequent toxic species, belonging to different families, were selected: Agave angustifolia, Catharanthus roseus, Duranta erecta, Ficus benjamina and Mangifera indica. Samples were collected in the two squares with the highest occurrence of toxic plants. Leaf anatomy and histochemistry techniques were applied, including sectioning, fixation, staining, slide mounting, and microscopic observation, aiming at the structural analysis of their systems and the identification of chemical compounds. The results showed a predominance of polygonal and isodiametric epidermal cells, as well as epidermis with a thick cuticle, a characteristic associated with environmental resistance. The presence of hypostomatic stomata, trichomes, cystoliths, and dorsiventral mesophyll organized in most of the studied species was also observed. In histochemical tests, lipids, lignin, cellulose, phenolic compounds, and starch were identified in all species, in addition to the presence of alkaloids and calcium oxalate crystals in some of them, indicating toxic potential. Thus, the results contribute to morphological and taxonomic studies, broaden the understanding of plant adaptation to different environments and stress conditions, reinforce the importance of these species for urban landscaping and care in their selection for the prevention of intoxications, as well as the importance of studies on their chemical composition for pharmacological, medicinal, and environmental applications.