Format: ORAL

Hannelise Balduino, Elza Guimares, Silvia Machado

São Paulo State University, Botucatu, Brazil

Nectar is an essential trophic resource for many animals, playing an important role in plant-animal interactions. Amphilophium mansoanum (DC.) L.G. Lohmann (Bignoniaceae) is a liana with extranuptial nectaries (ENN), at the calyces margins, and nuptial annular nectariferous disk (NN) below the ovary, at the bottom of the floral tubes. The energetic content, the chemical composition, and the dynamics of nectar from both nectary types are different. These traits seem to be under selective pressure by the interacting animals since ENN is visited by ants, wasps, flies, and cockroaches, and the latter mainly by large-sized pollinating bees. The aim of this study was to understand the functioning of these nectaries based on ultrastructural evidences. The ENN released nectar since the bud stage, while the NN released nectar only during the anthesis. These patterns matched the changes in the cells machinery: For ENN, in the young bud stage, amyloplasts were scarce and since the pre-anthesis bud, the starch grains presented degradation signs and became almost absent, while cytoplasmic oil bodies, mitochondria, endoplasmic reticulum, and leucoplasts became more evident. For the NN, in the young bud stage amyloplasts were also scarce, but there were lipophilic bodies in plastids and vacuoles. However, at pre-anthesis stage there was a massive increase in amyloplasts abundance, Golgi bodies (fewer than in ENN), mitochondria and plastids with different contents. At anthesis, we observed an increase in cytoplasmic oil bodies, protein in the cytosol and starch grain degradation. These ultrastructural changes in ENN, evince a transition from hydrophilic to lipophilic secretion. In NN, in contrast, the population and morphology of organelles were consistent with hydrophilic secretion during the whole flowers lifetime. These differences in nectaries functioning may be linked to nectar features that attract specific animal groups, acting on protection and pollination mutualism throughout the flowers lifetime. (FAPESP-#2021/13392-0;#2021/10639-5)(CAPES-Code001)(CNPq-Proc.312799/2021-7;Proc.308982/2020-7)