Estrutura e função dos pneumatódios em raízes de Vanda híbrida (Orchidaceae): do macro ao micro

Abstract

The aerial roots present in Orchidaceae have anatomical characteristics that are efficient in optimizing the acquisition and use of water and nutrients. Among them, the formation of the velamen stands out, a simple or multiple epidermis, consisting of cells that die at maturity, which allows orchids to survive in environments with water scarcity or fluctuation. Some species have pneumatodes in the velamen. The aeration units correspond to a set of cells that include the region of the velamen above the aeration cells (the pneumatode), the aeration cells themselves, and the specialized cells of the cortex. The functioning of the aeration units is based on two non-exclusive hypotheses involving passive mechanisms. In this sense, this thesis is based on the central hypothesis that structural, chemical, and physiological variations directly influence the functional performance of the aeration units, modulating their efficiency and response to environmental conditions. It is structured in three chapters. In the first chapter, we propose that the functionality of the aeration units is anchored in the chemical composition of the walls of their different cell types and the rest of the canopy, which depends directly on the composition of their cell walls and adjacent layers, allowing dynamic adjustments in the opening and closing of the aeration channels in response to environmental variations. In the second chapter, we analyze the tolerance of the epiphytic hybrid Vanda subjected to flooding, determining whether the water saturation of the canopy leads to root oxidative stress with a systemic effect on plant metabolism, discussing the role of pneumatodes in root aeration. In the third, we present a summary of the results obtained in the form of scientific dissemination through a brochure, as well as an account of the author's academic experience, emphasizing the importance of pursuing a doctorate and valuing the educational path.