The uncommon cavitated secretory trichomes in Bauhinia s.s. (Fabaceae): the same roles in different organs

Cavitated secretory trichomes are characterized by a short or absent stalk that is connected to a secretory hollow head. They are rare structures in angiosperms; in Fabaceae, they have been recorded in only seven genera, including Bauhinia s.s. Because B. curvula and B. rufa exhibit glands that are responsible for attracting pollinators to flowers, this study aimed to test whether the cavitated secretory trichomes present in the flowers of these species have an attraction function. As leaf trichomes are commonly related to plant defence, comparative analyses of the morphology, ontogeny, ultrastructure and chemical profile of the secretory trichomes present in flowers and leaves were conducted. It was found that cavitated secretory trichomes are similar in their external morphology and development, regardless of the organ or species analysed. However, interspecific differences were found in the secretion process and chemical profile of the exudate. The differences found in the cavitated secretory trichomes between species indicate that they secrete distinct compounds, whereas the similarities found in these structures between vegetative and reproductive organs indicate that the cavitated trichomes have equivalent ecological functions within a species, probably in plant defence during organ development. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2016, 180 , 104–122.