Morphological and anatomical traits during development: Highlighting extrafloral nectaries in Passiflora organensis

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. Research HighlightsThe anatomical and ultrastructural characteristics and the presence of calcium oxalate crystals in the nectary tissue suggest novel strategies against herbivory in the genus Passiflora.

Age-dependent miR156-targetedSPLsare required for extrafloral nectary development inPassifloraspp

“…4b-c). Although all three characteristic nectary tissues (nectary epidermis, nectariferous parenchyma, and subnectariferous parenchyma; Cardoso-Gustavson et al, 2013; Macêdo et al, 2021; Moraes et al, 2022) were observed in Pe NT and Pe OE plants (Fig. 4d-f), the number of cells in each layer was strongly reduced in these plants (Fig.…”

“…2), suggesting that the ontogeny of these structures was affected by low SPL expression and that changes in leaf development affect the growth of EFNs. Although the morphology of EFNs was affected in miR156-OE Passiflora plants, their tissue patterning was similar to NT plants, with demarcated nectary epidermis and nectariferous and subnectariferous parenchyma (Lemos et al, 2017; Moraes et al, 2022). However, cell number was strongly reduced mostly in the parenchymatic tissues (Fig.4m, n).…”

“…For example, the abundance and complexity of EFNs increase in Turnera velutina as the plant progresses into the reproductive phase (Villamil et al, 2013). In Passiflora organensis, EFNs are absent in the juvenile vegetative stage, with the adult stage characterized by EFN formation on the abaxial side of the leaf lamina (Moraes et al, 2022).…”

“…Depending on the species, vegetative phase change can be accompanied by shifts in a wide variety of traits, including the formation of secretory structures (Leichty & Poethig, 2019). In many plant species, the development or increase in the abundance of extrafloral nectaries (EFNs) occurs as the plant ages (Villamil et al, 2013; Moraes et al, 2022; Kwok & Laird, 2012; Leichty & Poethig, 2019). For example, the abundance and complexity of EFNs increase in Turnera velutina as the plant progresses into the reproductive phase (Villamil et al, 2013).…”

“…The genus Passiflora is represented by more than 500 species distributed in four subgenera: Passiflora , Decaloba , Astrophaea , and Deidamioides , with the subgenus Passiflora being the most numerous of the genus (Feuillet & MacDougal, 2007; Pérez & d’Eeckenbrugge, 2017). Floral and extrafloral nectaries are common in many Passiflora species, making the genus relevant for studies on the evolution, development and ecology of nectaries and nectar metabolites (Apple & Feener, 2001; Cardoso-Gustavson et al, 2013; Rocha et al, 2009; Pérez & d’Eeckenbrugge, 2017; Moraes et al, 2022). Comparative analyses of EFN patterning suggest a shared developmental program with leaf development to create EFN diversity in Passiflora species.…”