ORIGINAL ARTICLE Morpho-histodifferentiation of Billbergia Thunb. (Bromeliaceae) nodular cultures Thaysi Ventura de Souza 1,2 & Julia Faillace Thiesen 3 & Ana Paula Lando 1 & Miguel Pedro Guerra 1 & Marisa Santos 1,3 Received: 6 November 2015 /Accepted: 15 March 2016 # Springer-Verlag Wien 2016 Abstract Nodule cultures are formed through an intermedi- ate morphogenetic route that lies between organogenesis and somatic embryogenesis. Although well described in many species, different aspects of the morphological and histologi- cal development of nodules remain to be clarified. Based on their threatened status and high ornamental value, Billbergia alfonsi-joannis and Billbergia zebrina, two epiphytic brome- liad species endemic to the South American Atlantic Forest, were studied. Nodular cultures were induced to grow from nodal segments taken from etiolated seedlings grown in vitro for 12 weeks in the dark on MS medium supplemented with 1 μM TDZ. Samples were taken for analysis weekly over 8 weeks of growth and analyzed under light, transmission electron, and scanning electron microscopes. Morphological and histological analysis showed that nodular clusters origi- nated from stem pericycles and consisted of a polycenter, cambial tissue, cortical parenchyma, and a covering tissue. The polycenter consisted of an organizational center dispersed in parenchymal tissue. Each organizational center was formed by a vascular system surrounded by a bundle sheath. A cambial tissue surrounded these polycenters, promoting the regeneration of new nodules and leading to the formation of buds and roots. Primary nodules could generate secondary nodules in a repetitive process. Thus, histological analysis revealed the origin and formation of nodular cultures. These new data will support the establishment of micropropagation protocols and regeneration on a large scale for these species. Keywords Histology . Billbergia zebrina . Billbergia alfonsi-joannis . Micropropagation . Ultrastructure Abbreviations AB Axillary bud BAF Billbergia alfonsi-joannis BZ Billbergia zebrina CA Cambium CC Cambial cell OC Organizational center LE Leaf LM Light microscopy LP Leaf primordia MC Meristematic cell MS Murashige and Skoog (1962) basal media NO Nodule NV Nodule vascularization PA Parenchyma PE Periderm PV Provascular cell RO Root SEM Scanning electron microscopy SN Secondary nodule ST Stem SNE Sieve neoelement TDZ Thidiazuron Handling Editor: Peter Nick * Thaysi Ventura de Souza thaysiventura@gmail.com 1 Programa de Pós-Graduação em Recursos Genéticos Vegetais, Universidade Federal de Santa Catarina, Rod. Admar Gonzaga, Km 3, Florianópolis SC 88034-001, Brazil 2 Instituto Federal de Educação, Ciência e Tecnologia Catarinense, Campus Camboriú, Rua Joaquim Garcia, sn, Camboriú SC 88340-055, Brazil 3 Departamento de Botânica, Universidade Federal de Santa Catarina, Campus Universitário, Florianópolis SC 88040-900, Brazil Protoplasma DOI 10.1007/s00709-016-0962-2