Desvendando a morfoanatomia floral de uma espécie amazônica de Lecythidaceae: estruturas secretoras em Couratari tenuicarpa A.C.Sm.

Abstract

The family Lecythidaceae holds great importance in the Amazonian flora, exhibiting complex floral modifications of the androecium related to interactions with pollinators. However, little is known about the floral secretory structures and their rewards. This study aimed to describe the floral morphoanatomy of Couratari tenuicarpa A.C.Sm, a Lecythidaceae species found in flooded areas of Itacoatiara-AM. The investigation characterized its secretory structures structurally and histochemically. Samples were fixed, embedded in resin, sectioned, stained with Toluidine Blue, and photographed under an optical microscope. The study revealed that the flower hood has two spirals, one of which terminates in a nectar chamber. The morphology of the nectariferous region shows whitish digitiform projections that release a translucent secretion identified as nectar due to the presence of glucose. These nectariferous projections are vascularized and exhibit an anatomical pattern composed of papillose epidermis and secretory parenchyma, both with dense cytoplasm and evident nuclei. Histochemical tests indicated the presence of polysaccharides, starch grains, lipids, essential oils, and proteins in the papillose epidermis and secretory parenchyma. Additionally, accumulation of phenolic compounds was detected in the secretory parenchyma. These chemical components in the flower’s nectar may influence plant-insect interactions by providing energy during secretion, serving as rewards for pollinators, defending against herbivory, and acting as chemical signals to attract specific pollinators, such as bees. This study provides novel data on floral secretory structures, not only for the genus Couratari, but also as the first records of anatomy and histochemistry of floral nectaries in the literature of the Lecythidaceae family. Thus, these findings significantly contribute to the structural and ecological understanding of these intricate structures and have implications for future taxonomic applications and evolutionary interpretations.