Floral extranuptial nectaries in Bignoniaceae from Argentina

Abstract

Extranuptial nectaries are found in almost all flowers of the studied species, and always on the calyx. Their shape varies from patelliform to cupuliform. Considering their anatomy, three groups of cells are distinguished: (i) a secretory stratum of cylindrical, elongated cells, resting upon (ii) a layer or a single basal cell, and (iii) a reduced group of subepidermic cells. Based upon these characteristics, the terms simple and complex are proposed to describe extranuptial nectaries with one or with many basal cells respectively. This anatomic nectary feature is maintained within the level of species, thus becoming a significant specific character. The two types of extranuptial nectaries can be found within a genus, constituting an important character to differentiate similar species.