Autoalelopatia da polpa funicular de um cacto colunar que ocorre em diferentes ecossistemas do Nordeste do Brasil

Abstract

The funicular pulp of fruits present in some Cactaceae is known to inhibit the germination of their own seeds. Furthermore, it has been reported in the literature that fruits can produce toxic or deterrent metabolites, often found in higher concentrations and diversities than in other plant organs, thus being able to prevent the germination of their own seeds. However, it has not yet been described in the literature how environmental conditions can influence the dynamics of this autoallelopathic effect. Therefore, the general objective of this dissertation was to evaluate the autoallelopathy of the funicular pulp of a columnar cactus that occurs in different ecosystems of Northeastern Brazil. We used as a study model the species Pilosocereus catingicola (Gürke) Byles & Rowley subsp. salvadorensis (Werderm.) Zappi (Cactaceae), which occurs in areas of Caatinga, a semiarid region of Northeastern Brazil; and in areas of Restinga, in the Brazilian coastal region. Furthermore, this columnar cactus species produces its fruits in the dry and rainy seasons. To achieve the general objective of this dissertation, this work was divided into two chapters. In the first chapter, the objective of the work was to perform the metabolite profile of the mucilaginous funicular pulp of the fruits of P. catingicola subsp. salvadorensis using the non-targeted metabolomics technique by Gas Chromatography coupled to Mass Spectrometry. The results for this chapter, it was possible to note 135 metabolites belonging to 19 chemical families. In addition, it was possible to conclude that environmental conditions directly influence the metabolism of the funicular pulp of the fruits of P. catingicola subsp. salvadorensis in different ecosystems, with the variations observed here being related to seasonality, resulting in differences between populations of the same species. In the second chapter of this dissertation, the objective of the work was to evaluate how seasonality and the ecosystem of occurrence influence the autoallelopathy exerted by the funicular pulp of the fruits of P. catingicola subsp. salvadorensis on the germination behavior of its seeds. The results for this chapter showed that the seeds produced in the rainy season, in both populations, presented higher germinability, shorter germination time and greater synchrony, with less uncertainty and variation in the germination process. However, the extracts of lower polarity (AcOEt and Hex) negatively influenced the germination behavior as the concentrations increased during the rainy season, for both populations. Therefore, we can conclude for this chapter that the effect of autoallelopathy is dynamic in nature, being influenced by the fruit production seasons and the ecosystem in which these populations are inserted. The results found in this dissertation provide a comprehensive view of the metabolic responses of this species to environmental conditions, highlighting its adaptive capacity and the role of seasonal conditions in directing its metabolism. In this context, extractions performed with different organic solvents revealed significant variations in the concentrations of compounds between seasons and populations, demonstrating that seasonality not only regulates metabolic synthesis, but also influences the distribution and predominance of metabolites, adjusting them to the environmental conditions of each period, influencing the autoallelopathic effect differently.