Format: ORAL

Kayna Agostini Leonardo Galetto Marlies Sazima

1 Depto of Natural Science, Mathematics and Education, Federal University of São Carlos, Araras, Brazil 2 Instituto Multidisciplinario de Biología Vegetal, Universidad Nacional de Córdoba, Córdoba, Argentina 3 Depto of Botany, State University of Campinas, Campinas, Brazil

The genus Mucuna (Fabaceae) shows explosive flower opening and an impressive radiation involving different pollinators. The aim of this study was to verify how anatomical and ecological traits affect the dynamics of nectar production in the genus Mucuna which have a diversity of vertebrate pollinators. Mucuna japira (pollinated by birds) inflorescence bears 12-21 yellow flowers, which are in anthesis for seven days, whereas M. urens (pollinated by bats) inflorescence bears 36-54 greenish flowers, but only 1-3 flowers are in anthesis simultaneously, that last one night. Related to floral morphology, the reproductive organs are enclosed in the keel, being released after explosive flower opening. At the tip of the keel, the petals are stiff and united, which probably act as support to trigger flower explosion. In the non-lignified part of the inner epidermis occur entwined secretory papillae, which keep the petals firmly united. Both species had constant nectar sugar concentration (ca. 10% for M. japira and ca. 16% for M. urens) and secreted high volumes of nectar (ca. 340l per flower for M. japira and 310l per flower for M. urens), during five days for M. japira and six hours for M. urens, but nectar production stops immediately when flower opening mechanism is triggered. Nectar resorption occurred in both species since there is no longer any chance of flower being pollinated. Both species of Mucuna are dependent on their pollinators to produce fruits and seeds, but they have different strategies to promote the necessary interaction with birds or bats, especially related to nectar and flower traits. Also anatomical traits can mediated pollinators visitation as secondary wall thickenings of the inner mesophyll exist only in M. japira flowers, which are more difficult to open than those of M. urens.