Strategies for the protection of shoot buds in phanerophyte and geophyte species of Homalolepis Turcz. (Simaroubaceae, Sapindales)

Several structural attributes associated with the buds of shoot apices of angiosperms have been related to protection both at the mechanical and chemical defense levels. Although several characteristics related to the protection of shoot buds are known in different taxa of Sapindales, their occurrence in the neotropical genus Homalolepis (Simaroubaceae) are still unknown. Homalolepis includes 28 species mostly with extra-Amazonian distribution, occurring mainly in the Brazilian domains of the “Cerrado” and the Atlantic Forest. Its species vary widely in terms of habit, many of which are considered adaptations to the environments in which they occur. In this study, usual light and scanning electron microscopy techniques were applied in order to analyze the morphoanatomical and histochemical characteristics associated with the protection of apical and lateral shoot buds in phanerophyte (H. arenaria Devecchi & Pirani (Devecchi & Pirani), H. glabra (Engl.) Devecchi & Pirani and H. insignis (A.St.-Hil. & Tul.) Devecchi & Pirani) and geophyte (H. pumila Devecchi & Pirani, H. salubris (Engl.) Devecchi & Pirani and H. suffruticosa (Engl.) Devecchi & Pirani) species. Glandular prophylls, cataphylls, suberized layer on the leaf primordium, colleters, non-glandular trichomes, as well as a secretory canal with precocious development in the leaf primordium are among the characteristics that can be considered strategies for the protection of shoot buds in the studied species. Such structures are related to physical (cataphyll and suberized layer) and chemical (prophylls and secretory canal) protection or both (trichomes), against desiccation or attack by herbivores.