Floral biology and reproductive system of physic nut (Jatropha curcas L., Euphorbiaceae) in 'Recôncavo da Bahia', Brazil.

Understanding the floral and reproductive biology of botanical species is crucial for the development of strategies in plant breeding systems. Jatropha curcas L. is a promising species for the manufacture of biofuels, being previously studied mainly in genetic improvement to develop characteristics suitable to biofuels. In order to contribute with data for hybridization and breeding programs, this paper studies the floral biology and reproductive system in two experimental populations of different ages of Jatropha curcas in Cruz das Almas/BA. Both of them were examined about their anthesis, durability, number of flowers, stigma receptivity, P:O ratio, and reproduction tests. As observed, Jatropha curcas is a monoecious species and its flowering occurs between September and April. Inflorescences are composed of unisexual flowers with daytime anthesis (♂: 05-06h; ♀: 07-08h), where the staminates last 10h and pistillates 60h. The physic nut is self-compatible, forming fruits by self-fecundation and cross-pollination, although the greatest number of fruits/seeds is generated by natural pollination. Experiment 02, presented a larger number of flowers, probably due to the plant's age and physiology. Performing artificial pollination between 08:00h and 09:30h is recommended for larger production since the stigma is receptive and the flowers have a large amount of pollen available.