a b s t r a c tBignoniaceous woody species are very important ecological components of neotropical forests, but the reproductive biology of many species, such as Cybistax antisyphilitica, remains virtually unknown. Most species of Bignoniaceae are characteristically self-sterile, despite typically exhibiting normal pollen tube growth throughout the style, combined with slow rates of ovule penetration, fertilisation and endosperm initiation in selfed pistils. Uniform abortion occurs within a few days of anthesis, indicating the occurrence of late-acting self-incompatibility (LSI). However, breeding system studies have been performed in fewer than 7% of species, and other types of breeding systems (e.g., self-compatibility and apomixis) have been reported in this family. In the present study, the reproductive biology of C. antisyphilitica was investigated by field observation of flower visitors and floral events. Moreover, reproductive biology of this species was examined through experimental pollinations, analyses of pollen tube growth and ovule penetration using fluorescence microscopy, verification of pistil longevity, and a histological analysis of unpollinated vs. self-pollinated pistils. Finally, morphological aspects, quantities and germination were investigated in seeds that resulted from different pollination treatments. Natural pollination was effected by largeand medium-sized bees, and their visiting behaviour favours a high proportion of geitonogamy and no pollen limitation. Self-pollinated flowers produced no fruits, and all of the characteristic post-pollination events cited above were verified, witnessing the occurrence of LSI with post-zygotic rejection of selfed pistils in C. antisyphilitica. Although some indications of extended pistil longevity were found in selfed pistils, this feature seemed to be affected by unidentified environmental factors. The seeds were always monoembryonic and with high viability. A larger variation in the number of viable seeds was found in fruits derived from natural pollination. A low fruit set was observed after both natural and crosspollination, and most crossed fruits underwent abortion at several points during the juvenile phase, even when protected against herbivory. The formation of surplus flowers/juvenile fruits and the apparently wasteful selfing mechanism control implied in LSI are discussed in the context of the perennial life style of tropical woody plant species.

O Parque Nacional da Serra da Canastra localiza-se no sudoeste de Minas Gerais (20º00'-20º30'S e 46º15-47º00'W) e apresenta ca. de 40% de sua área coberta por campos rupestres. Foram registradas 41 espécies de Papilionoideae reunidas em 23 gêneros e oito tribos: Phaseoleae (Camptosema, Centrosema, Clitoria, Collaea, Eriosema, Erythrina, Galactia, Periandra e Vigna), Dalbergieae (Andira, Dalbergia, Machaerium, Platypodium, Poiretia, Stylosanthes e Zornia), Sophoreae (Acosmium e Bowdichia), Crotalarieae (Crotalaria), Desmodieae (Desmodium), Genisteae (Lupinus), Millettieae (Platycyamus) e Swartzieae (Swartzia). Os gêneros mais representativos em número de espécies foram Galactia (com cinco espécies), Andira, Eriosema, Vigna e Zornia, com três espécies cada um. Os gêneros Centrosema, Collaea, Crotalaria, Lupinus, Periandra e Stylosanthes foram representados por duas espécies, e os demais gêneros por uma espécie cada. A distribuição geográfica de Eriosema prorepens Benth., Lupinus subsessilis Benth. e Periandra gracilis H.S. Irwin & Arroyo foi ampliada neste trabalho. São apresentadas chaves para identificação, descrições e dados sobre a distribuição geográfica das espécies e táxons infra-específicos.