Prenner Gerhard, Cardoso Domingos, Zartman Charles E, de Queiroz Luciano P
Royal Botanic Gardens, Kew, Jodrell Laboratory, Richmond, Surrey, TW9 3DS, UK
Departamento de Botânica, Instituto de Biologia, Universidade Federal da Bahia, Rua Barão de Jeremoabo, s/n, Ondina 40170-115, Salvador, Bahia, Brazil Programa de Pós-Graduação em Botânica (PPGBot), Universidade Estadual de Feira de Santana, Av. Transnordestina, s/n, Novo Horizonte 44036-900, Feira de Santana, Bahia, Brazil.
Am J Bot. 2015 Nov;102(11):1780-93. doi: 10.3732/ajb.1500348. Epub 2015 Nov 2.
Floral development can help to shed light on puzzling features across flowering plants. The enigmatic Amazonian monospecific genus Petaladenium of the legume family (Leguminosae) had rarely been collected and only recently became available for ontogenetic studies. The fimbriate-glandular wing petals of P. urceoliferum are unique among the more than 19000 legume species. Ontogenetic data illuminate the systematic position of the genus and foster our understanding on floral evolution during the early diversification of the papilionoid legumes.
Flower buds were collected in the field, fixed in 70% ethanol, and investigated using scanning electron microscopy (SEM). Results were compared with existing material from early-diverging papilionoid legumes.
Formation of sepals and petals shows bidirectional tendencies. Stamens arise in two whorls, and the single carpel arises concomitantly with the outer stamen whorl. Gland formation starts early on the edges of the wing petals. The carpel reopens for a short time when the initiation of ovules is visible. Stomata at the base of the hypanthium indicate that the flower functions like other standard flag blossoms.
The floral ontogeny confirms the close affinity of P. urceoliferum with the florally heterogeneous, early-diverging papilionoid Amburaneae clade. The results strengthen the theory of a distinct experimental phase among early-branching papilionoid legumes during which a wider range of floral morphologies arose. Polysymmetry, monosymmetry, variable organ numbers, and a wide range of ontogenetic patterns laid the foundation for a successful canalization toward the more restricted but well-adapted dorsiventral papilionoid flag blossom.
花的发育有助于揭示开花植物中令人困惑的特征。豆科（豆科）神秘的亚马逊单种属花瓣腺属很少被采集到，直到最近才可用于个体发育研究。在超过19000种豆科植物中，壶形花瓣腺的流苏状腺质翼瓣是独一无二的。个体发育数据阐明了该属的系统位置，并增进了我们对蝶形花亚科豆科植物早期多样化过程中花进化的理解。
在野外采集花芽，固定在70%乙醇中，并用扫描电子显微镜（SEM）进行研究。将结果与早期分化的蝶形花亚科豆科植物的现有材料进行比较。
萼片和花瓣的形成呈现双向趋势。雄蕊分两轮出现，单个心皮与外轮雄蕊同时出现。腺体在翼瓣边缘早期开始形成。当胚珠开始可见时，心皮会短暂重新开放。花托基部的气孔表明该花的功能与其他标准旗瓣花相似。
花的个体发育证实了壶形花瓣腺与花形态多样、早期分化的蝶形花亚科安布拉内族分支关系密切。结果强化了早期分支的蝶形花亚科豆科植物存在一个独特实验阶段的理论，在此期间出现了更广泛的花形态。多对称性、单对称性、可变的器官数量以及广泛的个体发育模式为成功向更受限但适应性良好的背腹蝶形花亚科旗瓣花进化奠定了基础。
