The reproductive biology of Spathodea campanulata was investigated by means of hand-pollination experiments, observations of pollen tube growth using fluorescence microscopy, and serial sections of ovules in selfed and crossed pistils. Only cross-pollinated flowers developed fruits, and all selfed flowers abscised within 3-4 d. However, self pollen tubes grew successfully to the ovary, penetrating and fertilizing the majority of ovules by 48 h, indicating that S. campanulata is a species with late-acting self-incompatibility. The incidences of ovule penetration, fertilization and endosperm initiation were all significantly slower in selfed vs. crossed pistils, although no other signs of malfunctioning were detected. The possible role of such slow self pollen tube effectiveness as a recognition event is discussed within the context of the slow but not entirely suppressed self pollen tube growth reported for some species with conventional homomorphic self-incompatibility.
Recebido em 12/02/2010. Aceito em 28/06/2010 RESUMO -(Sistema reprodutivo do Ipê-Branco -Tabebuia roseo-alba (Ridley) Sandwith (Bignoniaceae)). Estudos sobre sistemas reprodutivos têm indicado o predomínio da autoincompatibilidade de ação tardia (AIT) em Bignoniaceae, embora poucas espécies tenham sido investigadas e ocorram outros tipos de sistemas reprodutivos na família. O presente estudo objetivou determinar o sistema reprodutivo de T. roseo-alba através de experimentos de polinizações controladas, análise histológica dos eventos posteriores à polinização, verifi cação do desenvolvimento in situ dos tubos polínicos e testes de germinação de sementes. Apesar de os tubos polínicos penetrarem e fecundarem a maioria dos óvulos em pistilos autopolinizados, o aborto de 100% dos mesmos foi verifi cado e, embora sua abscisão tenha ocorrido entre o quarto e o sexto dia após o início da antese, observou-se um ligeiro crescimento dos óvulos e do ovário precedendo a abscisão, porém inferior ao crescimento nos pistilos submetidos à polinização cruzada. A endospermogênese inicial e a formação do tubo proembriônico também foram mais lentas nos pistilos autopolinizados. A longevidade dos pistilos autopolinizados foi maior que a de pistilos não polinizados, e a taxa de germinação de sementes foi de 93%, sendo todas as sementes monoembriônicas. Os resultados demonstram que T. roseo-alba é espécie auto-estéril, destituída de poliembrionia e que apresenta AIT pós-zigótica. Palavras-chave: autoesterilidade, autoincompatibilidade de ação tardia, endospermogênese, tubo proembriônico ABSTRACT -(Breeding system of the White Trumpet Tree -Tabebuia roseo-alba (Ridley) Sandwith (Bignoniaceae)). Breeding system studies have indicated the predominance of late-acting self-incompatibility (LSI) in Bignoniaceae, despite the relatively few species investigated, and the occurrence of other kinds of breeding systems in this family. This study aimed to determine the breeding system in T. roseo-alba by means of controlled experimental pollination, histological analysis of post-pollination events, and studies of pistil longevity, in situ pollen tube growth and seed germination. Despite pollen tube penetration and fertilization of most ovules of selfed pistils, 100% of these pistils aborted uniformly between the fourth and sixth day after anthesis onset. Ovary and ovule growth, as well as initial endospermogenesis and proembryonal tube formation were verifi ed in selfed pistils before abscission, but the progress of post-pollination development in these pistils was slower than in crossed pistils. The longevity of self-pollinated pistils was greater than in non-pollinated pistils. Seed germinability was 93%, and all seeds were monoembryonic. These results show that T. roseo-alba is a species with post-zygotic LSI, and with no polyembryony.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.