Structural Characterization of Mint (Mentha x villosa Huds) Stem and Leaf

Abstract

Aims: The objective of this study was to identify the structural characteristics of the shoots of Mentha x villosa Huds and also, identify the main structures responsible for the production of active principles.
 Methodology: The analyzes were performed with stems and leaves from adult and healthy plants, which presented a uniform morphological pattern. The materials selected for the anatomical analyzes were fixed in FAA for 24 hours and after this period conditioned in 70% alcohol. Cross-sections and paradermic sections were manually made with a cutting blade. For sections analysis, 1% sodium hypochlorite was used for discoloration and safranine 10% dye for tissue staining.
 Results: The leaf of Mentha x villosa Huds presents asymmetric mesophyll, formed by palisade and lacunar parenchyma, and uniseriate epidermis. The diacytic stomata are located on the abaxial surface of the leaves with different sizes, all having a substomatal chamber. On both sides of leaves, glandular trichomes were observed in great quantity. The leaf midrib is formed by a large vascular bundle, with xylem facing the adaxial surface and phloem facing the abaxial surface. The stem presents uniseriate epidermis and below it can be found one or two layers of colenchyma. The vascular bundle consists of four main xylem points, and externally to it is found the phloem, which gives the quadrangular shape to the stem. Mentha x villosa Huds has characteristics that are common to aromatic species of the Lamiaceae family, which makes its characterization and differentiation difficult, as for example, its secretory structures which do not have taxonomic importance for differentiation on this species, since they are similar in other species of the same family.
 Conclusion: However, Mentha x villosa has a larger number of cell layers in the lacunar parenchyma, which is an important characteristic for the differentiation of species.