Morfoanatomia, perfil químico e atividade alelopática de três espécies de Copaifera L. (Leguminosae Caesalpinioideae) nativas da Amazônia

Abstract

Species belonging to the Copaifera L. genus (Leguminosae) are widely utilized in the Amazonian popular medicine, and its oils are considered to be one of the more important natural medicines of the forest. Despite its great importance, there are few studies concerning the morphological and anatomical characteristics of the genus, especially those describing its reproductive structures. Particularly, the taxonomic characterization of the Amazonian species of Copaifera deserves more attention. This way, this study aimed to characterize the morphological aspects of fruits, seedlings and saplings of Copaifera martii Hayne, C. duckei Dwyer and C. reticulata Ducke. The seeds, eophylls and metaphylls morpho-anatomy was also studied, as well as the occurrence and distribution of metabolites. Particularly, we aimed to better describe the taxonomic distinction between C. duckei and C. reticulata, the two closely related Copaifera Amazonian species. The possible allelopathic effects of the essential oil from leaves and stem of these species were also verified. The fruit of the three species are legumes. The seed coat surface, when observed in electronic microscopy, showed to be predominantly punctuated in C. duckei and C. martii, and microreticulate in C. reticulata. The cotyledons are recovered with a thin, slightly striated cuticle in C. duckei, while the cuticle of the other two species is clearly striated. The outer periclinal wall of the epidermis is slightly convex and presents depressions in C. duckei, being convex in the other two species. The embryonic axis of C. duckei presents small diameter in relation to its length, while in C. martii and in C. reticulata these measures are proportional. C. duckei and C. martii presents rudimentary plumule, displaying one and two protuberances in the apex, respectively, but in C. reticulata, the plumule is poorly differentiated, once it presents leaflets in the initial stages of development. The mature seeds of the three species present phenolic compounds and alkaloids, which are probably the main defense substances of the tegmen and the epidermis of the cotyledons. Lipids and proteins are the main reserve substances of the epidermis and the parenchyma of the cotyledons. The main difference observed among the saplings of the three species is the presence of well-developed, foliaceous stipules in C. reticulata, which are absent in C. duckei and are similar to those of the seedlings in C. martii, being also foliaceous but less conspicuous. C. martii presents alternate phyllotaxy, while the other species presents opposite phyllotaxy. We detected several metabolites in the foliar limb, such as starch, lipophilic and pectic substances, and mucilaginous, crystal and phenolic idioblasts. Eophylls and metaphylls are anatomically similar. The three species present secretory cavities and glands. The allelopathic activity of essential oil from stem and leaves of the studied species did not revealed significant differences in the two species tested (Mimosa pudica L. e Senna obtusifolia (L.) H.S. Irwin e Barneby). However, essential oil from leaves displayed higher potential to inhibit roots (45%) and hypocotyls (74%) development. Additionally, the major constituents detected showed to be more concentrated in the leaves than in the stem, which explains the differences observed on the effects intensity of the oils obtained. Among the identified constituents, only the  candinen and the linalol were previously reported to have allelopathic activity, being presented, in this work, the potential allelopathic activity of other compounds. Results obtained here contribute to the characterization of the morphological, anatomical and histochemical aspects of fruits and seeds of three Copaifera species. Also, we described the morphological traits of seedlings and saplings of these species, contributing to the taxonomic distinction between the taxa, especially between C. duckei and C. reticulata.