Agradecimentos: We cordially acknowledge Elliot Kitajima and Renato Salaroli for support with SEM and EDX analysis; CMI-FOP/UNICAMP for the access to the TEM. A.P.M. and M.C.D. acknowledge CNPq (312.602/2019-7 and 301.017/2019-0, respectively). This work was financially supported by the Coordination for the Improvement of Higher Education Personnel (CAPES) (finance Code 001), and São Paulo Research Foundation (FAPESP) (grants 2015/25633-1, 2018/12853-1, and 2018/21469-0), in Brazil Ver menos

Abstract: Passiflora organensis is a small herbaceous vine with characteristic morphological variations throughout its development. The plant bears button-shaped extrafloral nectaries exclusively in adult leaves. Extrafloral nectaries are structures that secrete nectar and play an important role in plant–animal interactions as a strategy for protecting plants against herbivory. In this work, we performed anatomical and ultrastructural studies to characterize P. organensis extrafloral nectaries during their secretory phase. We showed extrafloral nectaries in Passiflora organensis are composed of three distinct regions: nectary epidermis, nectariferous parenchyma, and subnectariferous parenchyma. Our data suggests that all nectary regions constitute a functional unit involved in nectar production and release. The high metabolic activity in the nectary cells is characterized by the juxtaposition of organelles such as mitochondria and plastids together plasmalemma. In addition, calcium oxalate crystals are frequently associated to the nectaries. An increasing concentration of calcium during leaf development and nectary differentiation was observed, corresponding to the calcium deposition as calcium oxalate crystals. This is the first description of extrafloral nectaries in Passiflora organensis that is a promising tropical model species for several studies Ver menos