Department of Botany, Institute of Biosciences, UNESP-Univ Estadual Paulista, Campus de Botucatu, Brazil.
Ann Bot. 2012 Jun;109(7):1243-52. doi: 10.1093/aob/mcs053. Epub 2012 Mar 28.
Several members of Bromeliaceae show adaptations for hummingbird pollination in the Neotropics; however, the relationships between floral structure, nectar production, pollination and pollinators are poorly understood. The main goal of this study was to analyse the functional aspects of nectar secretion related to interaction with pollinators by evaluating floral biology, cellular and sub-cellular anatomy of the septal nectary and nectar composition of Ananas ananassoides, including an experimental approach to nectar dynamics.
Observations on floral anthesis and visitors were conducted in a population of A. ananassoides in the Brazilian savanna. Nectary samples were processed using standard methods for light and transmission electron microscopy. The main metabolites in nectary tissue were detected via histochemistry. Sugar composition was analysed by high-performance liquid chromatography (HPLC). The accumulated nectar was determined from bagged flowers ('unvisited'), and floral response to repeated nectar removal was evaluated in an experimental design simulating multiple visits by pollinators to the same flowers ('visited') over the course of anthesis.
The hummingbirds Hylocharis chrysura and Thalurania glaucopis were the most frequent pollinators. The interlocular septal nectary, composed of three lenticular canals, extends from the ovary base to the style base. It consists of a secretory epithelium and nectary parenchyma rich in starch grains, which are hydrolysed during nectar secretion. The median volume of nectar in recently opened 'unvisited' flowers was 27·0 µL, with a mean (sucrose-dominated) sugar concentration of 30·5 %. Anthesis lasts approx. 11 h, and nectar secretion begins before sunrise. In 'visited' flowers (experimentally emptied every hour) the nectar total production per flower was significantly higher than in the 'unvisited' flowers (control) in terms of volume (t = 4·94, P = 0·0001) and mass of sugar (t = 2·95, P = 0·007), and the concentration was significantly lower (t = 8·04, P = 0·0001).
The data suggest that the total production of floral nectar in A. ananassoides is linked to the pollinators' activity and that the rapid renewal of nectar is related to the nectary morphological features.
在新热带地区，几个菠萝科成员表现出适应蜂鸟传粉的特征；然而，花部结构、花蜜产生、传粉和传粉者之间的关系还了解甚少。本研究的主要目标是通过评估凤梨属 Ananas ananassoides 的花部生物学、隔膜蜜腺的细胞和亚细胞解剖结构以及花蜜组成来分析与传粉者相互作用相关的花蜜分泌的功能方面，包括对花蜜动态的实验研究。
在巴西热带稀树草原的凤梨属 Ananas ananassoides 种群中，对花的开花和访花者进行了观察。使用标准方法对蜜腺进行了光镜和透射电镜处理。利用组织化学法检测了蜜腺组织中的主要代谢物。通过高效液相色谱（HPLC）分析了糖的组成。从套袋花（“未访问”）中确定积累的花蜜，并在实验设计中评估花朵对重复花蜜去除的反应，模拟传粉者多次访问同一朵花（“访问”）在开花过程中的情况。
蜂鸟 Hylocharis chrysura 和 Thalurania glaucopis 是最常见的传粉者。由三个透镜状通道组成的中隔隔膜蜜腺从子房基部延伸到花柱基部。它由分泌上皮和富含淀粉粒的蜜腺实质组成，淀粉粒在花蜜分泌过程中被水解。刚开放的“未访问”花朵的花蜜中值体积为 27.0 µL，平均（以蔗糖为主）糖浓度为 30.5%。开花持续约 11 小时，花蜜分泌在日出前开始。在“访问”花朵（每隔一小时排空花蜜）中，每朵花的花蜜总产量（体积：t = 4.94，P = 0.0001；糖质量：t = 2.95，P = 0.007）显著高于“未访问”花朵（对照），而浓度显著降低（t = 8.04，P = 0.0001）。
数据表明，凤梨属 Ananas ananassoides 总花蜜产量与传粉者的活动有关，而花蜜的快速更新与蜜腺的形态特征有关。
