Revealing the development of secretory structures in the leaves of Clusia fluminensis and Clusia lanceolata (Clusiaceae)

Abstract

Clusia (Clusiaceae) species are known for their large ecological and pharmacological relevance, which are associated with the presence of secretory structures found in all plant organs, such as colleters and secretory ducts. Despite their importance, detailed aspects on the origin and development of such remarkable structures remains unknown and understanding their structure and activity ranges will contribute to taxonomic, phylogenetic and pharmacological studies. In this sense, we aimed to analyze secretory structures in Clusia fluminensis and Clusia lanceolata leaves to answer the following questions: (i) how does the ontogeny process occur? (ii) which classes of substances are produced by these secretory structures? (iii) how does the secretory process occur? For this it was used light, epifluorescence, confocal and electron microscopy. Colleters and secretory ducts were found in C. fluminensis and C. lanceolata leaves. The colleters have their origin in the protoderm and subepidermal layers of ground meristem and produce mucopolysaccharides and phenols when matured. Some indicatives imply that the entire structure is involved in the granulocrine secretory process. The latex ducts presented schizogenous origin in both species. In the leaf primordia these ducts incorporate meristematic cells by the end of already formed stem ducts. These meristematic cells undergo mitotic divisions and the middle lamella between them dissolute, causing the formation of the lumen. In expanded leaves such cells are distributed throughout the leaf lamina and present branches. Epithelial cells produce latex, which is secreted by a granulocrine process. Based on the nature of the secretions and the early development, colleters and latex ducts seems to be involved in the plant defense.