Leaf anatomy and histochemistry of secretory structures of Zanthoxylum caribaeum Lam. (Rutaceae)

Rutaceae species, especially of the genus Zanthoxylum L., are known for possessing a well-diversified chemical composition with high potential for pharmacological activity. A variety of Zanthoxylum species are distributed throughout Brazil. This study aimed to characterize the leaf anatomy and identify the histochemical composition of the secretory material from the secretory structures of Z. caribaeum leaves. Leaves of Z. caribaeum were collected and processed for anatomical, histochemical and micromorphological characterization following standard methodologies. The leaves have an unstratified epidermis and glandular trichomes in epidermal depressions on the abaxial surface. Extrafloral nectaries were also observed on the abaxial surface. The leaf is hypostomatic and the stomata are anomocytic. The mesophyll is dorsiventral and has secretory cavities. The mesophyll cavities produce a secretion of lipidic nature and the cavities on the leaf margin produce a secretion of mixed nature, with neutral lipids and essences. In summary, our findings show that the leaves of Z. caribaeum have secretory structures like glandular trichomes that can function as extrafloral nectaries and cavities. The characterization of the leaf anatomy of Z. caribaeum can provide relevant data for future taxonomic studies of the genus.