Institute of Biosciences, Department of Botany, São Paulo State University - UNESP, Botucatu, São Paulo, 18618-970, Brazil.
Protoplasma. 2020 Jul;257(4):1139-1148. doi: 10.1007/s00709-020-01499-9. Epub 2020 Mar 15.
Floral fragrances play an important role in pollinator attraction; they serve as signals for primary rewards such as nectar. The presence of osmophores (a specialized glandular tissue that produces fragrance) in the terrestrial orchid Cyclopogon has only been described in a single species. There are fragrant and odorless species within this genus, but no data on the similarities or differences between them has been published. Here, we present new data on the lip morphology and ultrastructure from eight Cyclopogon species to better understand the mechanisms of pollinator attraction of this group. To achieve this goal, we used light, scanning, and transmission electron microscopy. Five out of eight species presented globular trichomes associated with fragrance production on the abaxial side of the labellum. Together with subepidermal cells, they compose the secretory tissue. Despite the absence of globular trichomes, C. apricus also presented cells associated with fragrance production. Lipid droplets, plastids containing plastoglobuli, and starch were indicators of secretory activity present in these species. This same pattern of fragrance production and release, associated with flower morphology, may result in the restriction of pollination by halictid bees.
花香在传粉者吸引中起着重要作用；它们是花蜜等主要奖励的信号。陆地兰花 Cyclopogon 中的香腺（一种产生香味的特殊腺组织）仅在一个物种中被描述过。该属内有芳香和无味的物种，但尚未发表关于它们之间相似性或差异性的数据。在这里，我们提出了关于 8 种 Cyclopogon 物种唇部形态和超微结构的新数据，以更好地了解该组传粉者吸引的机制。为了实现这一目标，我们使用了光学显微镜、扫描电子显微镜和透射电子显微镜。在 8 个物种中有 5 个物种在唇瓣的背面呈现出与香味产生有关的球状毛。它们与表皮下细胞一起构成了分泌组织。尽管缺乏球状毛，但 C. apricus 也呈现出与香味产生有关的细胞。脂滴、含有质体小球的质体和淀粉是这些物种中存在分泌活动的指标。这种与花朵形态相关的香味产生和释放模式可能会限制食蚜蝇科蜜蜂的授粉。
