Fenologia, polinização e reprodução de duas especies de Croton (Euphorbiaceae) em mata semidecidua

AUTOR(ES)

Luciana Coutinho Passos

DATA DE PUBLICAÇÃO

1995

RESUMO

The phenology, pollination and mating systems of Croton floribundus and C. priscus (Euphorbiaceae) were studied in a semideciduous forest in Campinas, São Paulo, from 1993 to 1994. The species are pioneer monoecious trees, that bear bissexual racemose inflorescences, with unissexual and inconspicuous flowers. These species blossom in the wet season, from October to December. Both species present protogyny within an inflorescence. Furthennore, the flowering sequence is syncronized so there is little or no overlap between pistillate and staminate flowers of an individual plant. There was a peak of pistillate flower production in the middle of the flowering period of both species of Croton. However, staminate flowers were more numerous. Staminate flowers of both species are scented, last one day, and open ca.O7:00 h in C. floribundus and ca.17:30 h in C. priscus. The pollen is powdery and its viability is ca.90% and 96%, respectively. Anthesis of pistillate flowers of C. floribundus and C. priscus is slow, and the flowers are receptive for 2 - 3 and 3 - 5 days, respectively. Flowers of both sexes produce nectar; the volume values were ca. 21 ml and 5 ml for pistillate flowers, and ca. 17ml and 3 ml for staminate flowers of C. floribundus and C. priscus, respectively. The mean sugar concentrations were 38% and 22% for pistillate flowers, and II % and 27% for staminate flowers of C. floribundus and C. priscus, respectively. Although both Croton species are visited by various insects, Syrphid flies are the main pollen vectors, particularly Omidia obesa and species of Palpada. The wind also mediates pollen transfer. Dichogamy is very accentuated and seems to reduce autogamy in these Croton species, which are selfcompatible. Both species also presented parthenocarpy, producing fruits with inviable seeds. We suggest that these Croton species may benefit from both fly and wind-pollination, and that flowering patterns may promote outcrossing in these species

ASSUNTO(S)

morfologia vegetal ecologia vegetal plantas - reprodução fenologia vegetal polinização croton (botanica)

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