Mimosa, one of the most species-rich genera in the Leguminosae, exhibits a high diversity of trichomes. These structures are considered crucial to the taxonomy of the genus and are commonly used to delimit infrageneric groups. The last taxonomic revision by Rupert C. Barneby, published in 1991, provided an important reference in the understanding of trichomes in Mimosa, but some terminology still needs to be clarified and standardized. The present study describes the microstructure and anatomy of trichomes in Mimosa and suggests a terminological standardization for these structures in the genus. We examined the trichomes of 62 species and the terms used to classify them were compared with previous taxonomic studies in the genus. We recognize 15 types of trichomes primarily based on the number, arrangement, and secretory activity of cells (uni- versus multicellular, uni- versus multiseriate, simple versus branched, glandular versus non-glandular). We conclude that the type of trichomes, rather than the type of indumentum, should be used for comparative analyses.
Prof. Lucas Sa Barreto Jordao is a Biologist, began his academic studies at the Rio de Janeiro Botanical Garden (JBRJ) during its graduation studying taxonomy of the genus Mimosa (Leguminosae). Obtained a master’s degree in Botany at the National Museum of Brazil in 2013 with a dissertation on floristic and taxonomic studies of Mimosa in the state of Rio de Janeiro, Brazil, and a doctorate in Botany at the JBRJ in 2019 with a thesis on phylogenetic studies based on molecular data and a taxonomic revision of four series of the genus. In 2016, he held an exchange where he worked at the New York Botanical Garden on the Reflora Project in which he digitized specimens from Brazilian flora stored at the NY herbarium, while developing part of his doctoral research. In 2019,he completed a post-doctorate at JBRJ exploring the use of many phylogenetic and biogeographic tools. He worked as a biology teacher in elementary and high school for six years. He also worked as a consultant in floristic surveys, forest inventories and botanical identification and, currently, he is a professor of Botany, Forensic Botany and Brazilian Environmental Law in a preparatory course for application processes of government jobs, and in a specialization course (“Post-graduation lato sensu”). Since March 2020, he has worked at National Center for Flora Conservation/JBRJ assessing endangered species. His interest in trichomes arose from the need to understand the morphological diversity of Mimosa.