Development, secretory activity and chemical composition of the resin in the ducts of Kielmeyera appariciana Saddi (Calophyllaceae)

• Autor(a) principal: Costa, Ellenhise Ribeiro
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/41/41132/tde-30112020-122346/
• topic: Composição da secreção; Ductos secretores; Metabolism; Metabolismo; Origem; Origin; Secretion composition; Secretory ducts; Ultraestrutura; Ultrastructure

Calophyllaceae are important representatives of the Brazilian Cerrado, presenting endemic and rare species. The family has a pantropical distribution and comprises 13 genera and 460 species in which Kielmeyera stands out due to the number of species, geographical distribution and economic importance. The species of Calophyllaceae are especially characterized by the presence of secretory ducts but there is no information on their mode of formation and secretory activity. This work aims to analyze the development, structure, secretory activity and composition of the secretion of the ducts of the Kielmeyera appariciana. Our results showed that the species has primary ducts in the cortex and pith and secondary ducts in the phloem. Both ducts are similar, being composed of a uniseriate epithelium surrounded by a sheath and with a lumen formed by schizogeny. However, the ducts differ in relation to the composition of the exudate. The chemical analyses, complemented by the histochemical localization, showed that the primary ducts produce resin, while the secondary ones produce gum. This is the first report of the occurrence of two types of ducts in the same organ. The analysis of the formation of the resin ducts also proved that they are schizogenous in which pectinase digests the middle lamella between the central cells of the rosette, releasing them from each other. Then, the cells split away by polarized growth, mediated by a reorganization of the cytoskeleton. With the differentiation of the epithelium, the cells initiate the secretory activity, identified by the accumulation of secretion in the cytoplasm. Asynchronously, epithelium cells start to die mediated by the release of reactive oxygen species, resulting in an accumulation of strongly colored substances in the cytoplasm, degradation of plastids and mitochondria, nuclear condensation and rupture of the tonoplast. Cellulase activity was detected in the walls of these cells, especially in the region facing the duct lumen, breaking the cell and releasing the exudate inwards. The role of the cytoskeleton in the formation of a schizogenous duct and the holocrine secretion mediated by programmed cell death are described for the first time for secretory ducts