DESVENDANDO A ESTRUTURA DOS DENTES CUCURBITOIDES EM ESPÉCIES DE CUCURBITACEAE

Abstract

Leaf teeth, i.e. projections of the leaf margin, are common among angiosperms and can differentiate in various aspects, e.g. in the presence or absence of an associated gland. Cucurbitoid teeth are related to the species Datiscaceae, Begoniaceae and Cucurbitaceae, all from order Cucurbitales. Although this type of tooth is associated with a gland and the guttation process has been observed, no structural characterization has been made to confirm the nature of this structure in Cucurbitaceae species. Thus, the objective of this work was to anatomically characterize and identify the nature of glands associated with cucurbitoid teeth in Cucurbitaceae species. Margin samples of leaves at different developmental stages were obtained from seven Cucurbitaceae species, fixed in FAA70 and processed following usual procedures in optical and scanning electron microscopies. Saplings of Cucumis sativus were placed in a humidity chamber to induce guttation for later glucose testing. Hydathodes were confirmed to occur in all studied species. Their structure consists of an uniseriate epidermis with aquifer pores, reduced epithem, absent sheath and terminal vascularization being formed exclusively by xylem. Only in Luffa cylindrica was a stratification in the tooth epidermis and a hypodermis layer. The presence of sugars in the exudate, which could confuse the hydratodes with hydratodes with nectaries, was discarded in the glucose test. We have characterized, for the first time, the structure of hydathodes in the Cucurbitaceae, thereby elucidating the structure of the glands associated with cucurbitoid teeth. Investigating tooth structure in the Begoniaceae and Datiscaceae should contribute to better knowing the order through taxonomic and biological perspectives.