Ontogenesis, histochemistry and seasonal and luminous environmental characterization of secretory cavities in leaves of Myrcia splendens (Myrtaceae)

Abstract

Secretory cavities are structures that secrete compounds that protects plants against herbivory and pathogenic microorganisms. These cavities have been reported in many genera. However, there are few studies on secretory cavity ontogeny in the genus Myrcia (Myrtaceae) as well as the effects of luminosity and seasonality on such secretory cavities. Therefore, the objective of this is to provide new information regarding the ontogenesis, structure, histochemistry and effects of seasonality in M. splendens. We collected and analyzed leaves from ten M. splendens specimens exposed to sun and shade during both wet and dry seasons. Samples were subjected to standard anatomical techniques for light microscopy. Myrcia splendens has schizo-lysigenous ontogenesis with exudates composed of lipids, essential oils, oil-resins and alkaloids. The largest secretory cavities were found in leaves exposed to sun during the dry season. The presence of lipophilic compounds may be an important strategy to plant protection against herbivores. The seasonal variations observed in the leaf secretory cavities demonstrate the anatomical plasticity of such species to light and water availability. As total area of leaf cavities in M. splendens reflects the seasonal variation, this should be taken into account when aiming to produce crops meant to essential oils/alkaloids extractions.