Nunes C E P, Amorim F W, Mayer J L S, Sazima M
Programa de Pós-Graduação em Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil.
Departamento de Botânica, Instituto de Biociências, Universidade Estadual Paulista "Júlio de Mesquita Filho", Botucatu, São Paulo, Brazil.
Plant Biol (Stuttg). 2016 Jan;18(1):15-25. doi: 10.1111/plb.12312. Epub 2015 Mar 26.
Relationships among floral biology, floral micromorphology and pollinator behaviour in bird-pollinated orchids are important issues to understand the evolution of the huge flower diversity within Orchidaceae. We aimed to investigate floral mechanisms underlying the interaction with pollinators in two hummingbird-pollinated orchids occurring in the Atlantic forest. We assessed floral biology, nectar traits, nectary and column micromorphologies, breeding systems and pollinators. In both species, nectar is secreted by lip calli through spaces between the medial lamellar surfaces of epidermal cells. Such a form of floral nectar secretion has not been previously described. Both species present functional protandry and are self-compatible yet pollinator-dependent. Fruit set in hand-pollination experiments was more than twice that under natural conditions, evidencing pollen limitation. The absence of fruit set in interspecific crosses suggests the existence of post-pollination barriers between these sympatric co-flowering species. In Elleanthus brasiliensis, fruits resulting from cross-pollination and natural conditions were heavier than those resulting from self-pollination, suggesting advantages to cross-pollination. Hummingbirds pollinated both species, which share at least one pollinator species. Species differences in floral morphologies led to distinct pollination mechanisms. In E. brasiliensis, attachment of pollinarium to the hummingbird bill occurs through a lever apparatus formed by an appendage in the column, another novelty to our knowledge of orchid pollination. In E. crinipes, pollinarium attachment occurs by simple contact with the bill during insertion into the flower tube, which fits tightly around it. The novelties described here illustrate the overlooked richness in ecology and morphophysiology in Orchidaceae.
在鸟媒传粉的兰花中，花生物学、花微观形态与传粉者行为之间的关系是理解兰科植物中丰富花多样性进化的重要问题。我们旨在研究大西洋森林中两种蜂鸟传粉兰花与传粉者相互作用的花部机制。我们评估了花生物学、花蜜特征、蜜腺和蕊柱微观形态、繁育系统及传粉者。在这两个物种中，花蜜由唇瓣胼胝体通过表皮细胞内侧片状表面之间的间隙分泌。这种花部花蜜分泌形式此前尚未有过描述。两个物种均表现出功能性雄先熟，自交亲和但依赖传粉者。人工授粉实验中的坐果率是自然条件下的两倍多，证明存在花粉限制。种间杂交未产生果实表明这些同域共存开花物种之间存在授粉后障碍。在巴西埃氏兰中，异花授粉和自然条件下产生的果实比自花授粉产生的果实更重，表明异花授粉具有优势。蜂鸟为这两个物种传粉，它们至少共享一种传粉者物种。花形态的物种差异导致了不同的授粉机制。在巴西埃氏兰中，花粉块通过蕊柱上一个附属物形成的杠杆装置附着在蜂鸟喙上，据我们所知，这也是兰花授粉的一个新特征。在毛埃氏兰中，花粉块在插入花管时通过与喙简单接触附着，花管紧密贴合喙部。这里描述的新特征说明了兰科植物在生态学和形态生理学方面被忽视的丰富性。
