Development of staminate and pistillate flowers of the hop (Humulus lupulus L. - Cannabaceae) with emphasis on the calyx and gynoecium

Abstract

Humulus lupulus L. (hop) stands out in the Cannabaceae family for its importance in the production of compounds such as lupulin extracted from its pistillate flowers for flavoring beer. This project aims to study the developmental stages of pistillate and staminate flowers of this species, in order to understand the processes that lead to the formation of atypical floral characteristics, such as the presence of a single whorl in the perianth and the unilocular and uniovulate gynoecium. For that, the following questions were formulated: (1) Is the flower apetalous, that is, is its perianth formed only by sepals? (2) Is the gynoecium in fact pseudomonomerous, that is, unilocular and uniovulate, but bicarpellate? (3) Are the two stigmatic branches functional? Do they result from the union of two carpels or from the division of the stigma of a single carpel, as occurs in species from closely related families (Ulmaceae and Moraceae)? (4) Do the characteristics related to the ontogeny of hop flowers corroborate the current position of the genus Humulus in Cannabaceae, close to Cannabis? For this purpose, samples of buds of various sizes and flowers will be collected from cultivated plants and processed for analyses in scanning electron microscopy, light microscopy, and epifluorescence. The knowledge about the development of hop flowers can be used in phylogenetic analyzes of Cannabaceae or even to direct extraction processes of its bioactive compounds.(AU)