NECTARY STRUCTURE AND NECTAR CHARACTERISTICS IN SOME BIGNONIACEAE

The nectary structure and chemical nectar composition of 15 species belonging to 12 genera of Bignoniaceae are analyzed. All taxa bear a conspicuous nuptial nectary surrounding the ovary base. The secretory tissue is mostly supplied by phloem branches. The stomata are located in the middle and upper part of the nectary epidermis with an homogeneous distribution. The nuptial nectary is proportionally large in relation to the ovary (15-30%), disregarding the nectary volume. Most species have extranuptial nectaries in both inner and outer surfaces of the calyx, Both kinds of nectaries lack a vascular tissue that straightly supplies them, Nuptial nectar concentration (wt/wt) ranges from 19 to 68%. Sugars and amino acids are found in all species. Half of the species have hexose predominant nectars, the remaining sucrose predominant. Phenols are detected in only three species, whereas reducing acids exclusively in Tecoma stans. Alkaloids and lipids were never detected. Extranuptial nectar chemical composition is analyzed in two species: Dolichandra cynanchoides and Podranea ricasoliana. Bees constitute the main flower visitors of the species studied whereas hummingbirds were seen visiting three species. A correlation analysis is performed with the data obtained. There are a few significant correlations which indicate a parallel increase of three parameters: the longer the flower length, the more voluminous the nectary and the higher stomata number, independently of the floral biotype. Phenograms are obtained using 24 floral characters including nectary and nectar data, The clusters obtained do not reflect taxonomic relationships but are useful in the understanding of animal-plant interactions when the flower biotype is considered.