Nuptial nectary structure of Bignoniaceae from Argentina

Abstract

Nuptial nectary characteristics were investigated in 37 taxa of Bignoniaceae. A nuptial nectary associated to the floral axis was found in all species. Two main types can be distinguished according to their degree of development and functionality: 1) vestigial and non-secretory and 2) well-developed and secretory. The former is characteristic of Clytostoma spp., while the latter is found in the remaining species. Two subvarieties of the secretory type of nectary can be discerned according to their position and shape: 1) annular, found in Adenocalymma, Amphilophium, Anemopaegma, Arrabidaea, Dolichandra, Eccremocarpus, Macfadyena, Melloa, Pithecoctenium, Tabebuia, and Tecoma, and 2) cylindrical, found in Argylia, Cuspidaria, Jacaranda, Mansoa, Parabignonia, Pyrostegia, and Tynnanthus. Anatomically, two tissues are distinguished: 1) a single-layered epidermis covered by a cuticle and a variable number of stomata, and 2) a secretory tissue composed of compactly arranged parenchyma cells. Both nectary size and nectary/ovary ratio were usually larger in lianas (Bignonieae) than in trees (Tecomeae). Nectary type proved to be consistent among species of same genus but not among genera of same tribe. Nectary features such as vascularization, presence of trichomes and nectary type were constant within the analyzed species and therefore have a reliable taxonomic value.