Format: ORAL

Gustavo Rojas-Alvarado1, Adam Karremans1

1 Jardín Botánico Lankester, Universidad de Costa Rica, Cartago, Apartado 302-7050, Costa Rica

Despite its great relevance, the study of the inflorescence from a typological point of view generally goes unnoticed in taxonomy, which is fundamental for the comparison of structural elements of the same origin. Pleurothallidinae is the most diverse subtribe in Orchidaceae is not the exception, its typology inflorescence remains largely unexplored, causing incorrect interpretations of its structures and misapplication of terms. The morphology of Pleurothallidinae inflorescences is clearly illustrated by photographs and diagrams, and it is analyzed and discussed from a typological point of view, based on the detailed study of structural elements of living material, including more than 82% of genera of the subtribe. The study shows that the subtribe presents a generalized type of inflorescences formed by an abbreviated peduncle and branch system that cannot be seen with the naked eye, which is an uncommon condition in other orchids groups. Each branch may produce coflorescences of different lengths with one or multiple flowers, also presenting different patterns of succession that determine the general appearance of the plant. There are two main types of inflorescences in Pleurothallidinae, these with single-flowered coflorescences that are dominant in early divergent clades, ant the multi-flowered coflorescences, which dominate higher clades. A general and practical classification is established for the different types of coflorescences according to the length and number of flowers produced.