DIFFERENCES IN FLORAL MORPHOLOGY, FLORAL NECTAR CONSTITUENTS, CAROTENOIDS, AND FLAVONOIDS IN PETALS OF ORANGE AND YELLOW PYROSTEGIA-VENUSTA(BIGNONIACEAE) FLOWERS

Orange-colored flowers of Pyrostegia venusta (Bignoniaceae) from the B razilian cerrado vegetation were analyzed and compared with yellow-col ored ones with regard to morphological parameters, nectar constituents , and petal pigments. In comparison to the yellow flowers, the more co mmon orange ones are characterized by a wider floral tube, a higher to tal nectar production, a higher sucrose content, a higher amino acid c ontent per volume, and a higher concentration of carotenoids in the pe tals. On the other hand; flavonoids are more concentrated in the yello w flowers. Legitimate floral visitation by hummingbirds and nectar rob bing by bees are discussed. However, a direct comparison of the newer visitors tvas not possible, since the whole mixed population was destr oyed by agricultural activity.