Ontogenia da flor à fase inicial do fruto de Leopoldinia pulchra Mart. (Arecaceae: Arecoideae)

Abstract

The ecological study of the reproductive phenology, morphoanatomy, and ontogenesis of flowers and immature fruits constituted the objective of this work, as well as verifying the incidence of parthenocarpy and the pseudomonomerous character to infer the reproductive behavior and flower development for understanding their relationship with the environment and tissue formation. The studied population of Leopoldinia pulchra Mart. is located in a remnant igapó forest in the municipality of Iranduba, Amazonas. Monitoring of reproductive behavior, investigation of parthenocarpy, flower biometric analysis during anthesis, and morphoanatomy of buds from spathe opening to the early stages of immature fruit development were conducted. The species showed an annual reproductive cycle that began during the ebb, with spathe emergence, and ended with seed dispersal at the start of the flood season. The fruits produced showed a high percentage of viable fruits compared to an insignificant percentage of parthenocarpic fruits. The inflorescence is a panicle branched into up to four orders, with 1,277 rachillae and an estimated 18,963 pistillate flowers. The flowering is protandrous, and the flowers are organized in triads or solitary. The staminate flowers are subsessile, with bracteoles, three imbricated sepals, and three valvate petals, presenting a uniseriate epidermis, homogeneous mesophyll with fibers, tannins, and fibrovascular bundles. The androecium consists of six dorsifixed stamens, and the sterile gynoecium is represented by a trilobed pistillode. The pistillate flowers are sessile, delimited by bracteoles, with three imbricated sepals and three valvate petals at anthesis. They present a papillose uniseriate epidermis and a similar homogeneous mesophyll. The trilocular and triovulate gynoecium develops only one campylotropous, bitegmic, and crassinucellate ovule. The stigma branches have unicellular papillae and form a stigmatic canal extending toward the locules. During fruit development, the formation of tanniferous tissue below the epidermis, the differentiation of a macroesclerid layer beneath it, the differentiation of clustered fibers associated with vessel elements, and meristematic activity in the inner mesocarp and locular epidermis were observed. These processes form an aggregated tissue set characterizing the endocarp as "cocosoid-arecoid". In the histochemical study, the epidermis of the floral whorls showed a lipidic cuticle; phenolic compounds were found in the parenchyma, ovule, and associated with fibrous clusters; tanniferous idioblasts occurred at different developmental stages across all structures; proteins were detected in fiber structures, stony cells, and pollen grains, which also contained starch grains. Throughout the phenological events and the development of reproductive organs, it was possible to understand the biological and reproductive cycle of the species and its main morphological and anatomical changes.