Much more than just a tooth: occurrence of hydathodes in the leaf teeth of Hydrocotyle asterias Cham. & Schltdl. (Araliaceae Juss.)

ABSTRACT

Although Araliaceae has many species with toothed leaf margins, the anatomical structure of these projections hasnever been investigated. The objective of this study was to characterize the anatomy of the leaf teeth of Hydrocotyle asterias Cham. & Schltdl., a representative of this family. Fragments of the leaf teeth were processed according to the usual techniques for optical microscopy (diaphanization and paradermal cuts) and scanning electron microscopy. The leaf tooth of H. asterias consists of hydathodes whose size, shape, and space between teeth vary among the different stages of leaf development. They have unstratified epidermis composed of isodiametric cells with slightly thickened walls, thin cuticle, and stomata concentrated at the apical region. Vascularization is composed of xylem that projects to the epithem. This study presents the first data on the anatomical structure of the leaf teeth of the Araliaceae family and expands the knowledge about the hydathodes associated with leaf teeth.

Keywords:
anatomy leaf; gland; leaf projections