Estudo da fenologia, dos constituintes químicos voláteis e interação inseto-planta em Piper mollicomum Kunth (Piperaceae) da Floresta da Tijuca

Abstract

Piper mollicomum Kunth can bring contributions to studies related to the insect-plant interaction, mainly because there are few chemical-ecological approaches regarding this species. Therefore, this work aimed to identify the potential pollinators, as well as to investigate the seasonal variation of essential oils (EOs) of the leaves and in different stages of the development of organs reproductive organs of this species. This research was carried out in two periods in Floresta da Tijuca, in the State of Rio de Janeiro, from October 2019 to February 2020; and September 2020 to January 2021. In the first, the inflorescences were randomly collected for analysis of the OEs, and in the second, the development of the reproductive organ was evaluated, and the OEs were extracted and analyzed in the different stages of development. Jointly, in the two observation periods, the frequency of visits by potential pollinators was evaluated. Finally, the chemical composition of the EOs was correlated with abiotic factors (macro- and microclimate variables) and with the frequency of visits by potential pollinators. The observations were made weekly, in the two periods, from 08:00 h to 17:00 h. The EOs were obtained by hydrodistillation in a modified Clevenger apparatus. Chemical characterization and quantification were performed by Gas Phase Chromatography (GC) coupled to Mass Spectrometry (MS) and by GC coupled to the Flame Ionization Detector (DIC), respectively. Elevated levels of 1,8-cineole and linalool were identified in leaves and reproductive parts of P. mollicomum in almost all investigation periods. Eupatoriochromene showed significant variation (p < 0.05) between leaves and stages of development of reproductive organs. The weekly observations showed a high frequency of bee visits; and the results related to the Spearman correlation showed a strong positive influence between the constancy of insects in the inflorescences and the relative percentage of linalool, E-nerolidol, camphene, aromadendrene and Z-β-ocimene. Microclimate meteorological variables, such as relative humidity, not only influence the biosynthesis of volatile constituents, but also the activity of visits by potential pollinators of P. mollicomum. These are the first records of the variation of the chemical constituents of EOs from leaves and reproductive organs during the entire flowering period of P. mollicomum, as well as the evaluation of the habits of potential pollinators of this plant in a fragment of the Atlantic Forest that is strongly threatened by actions anthropic.