New contributions to the leaf anatomy of eight Vanilla (Orchidaceae) species occurring in the Brazilian Amazon

Abstract Vanilla is a pantropical genus of 130 vine species, most of which are nomadic. It is most diverse in Brazil, which hosts thirteen endemic species, including two in the Amazon, its second-richest domain. Vanilla exhibits high morphological diversity, although identifying species requires flowers. Since the vegetative anatomy of Vanilla is still poorly understood, our objective was to conduct a comparative study of the leaves of eight species occurring in the Amazon, belonging to two subgenera: Vanilla subgen. Membranacea ( V. acuta and V. mexicana ) and Vanilla subgen. Vanilla ( V. appendiculata , V. lindmaniana , V. odorata , V. phaeantha , V. planifolia and V. pompona ), using standard protocols for light and scanning electron microscopy. We identified anatomical characters for Vanilla species, noting that the presence and type of crystalliferous idioblasts and crystal types proved most significant in distinguishing between them. For example, V. appendiculata lacks crystals, V. odorata has prismatic crystals, and V. phaeantha has prismatic crystals and raphides in the leaf blade. Other characters can be used to separate groups of taxa within the sample, such as the following: absence/presence of a hypodermis; and absence/presence, type, and location of crystals. The findings provide new diagnostic information for vegetative Vanilla , which is crucial for conservation efforts in Brazil’s Amazon, and offers a year-round tool for researchers studying this commercially important plant. This updated structural data is expected to guide future, larger systematic studies of the genus.