Graduate School of Life Sciences, Tohoku University, 6-3 Aoba, Sendai, 980-8578, Japan.
Am J Bot. 2018 May;105(5):842-850. doi: 10.1002/ajb2.1099. Epub 2018 Jun 12.
Plants that secrete abundant nectar attract many pollinator visits, potentially leading to a high frequency of geitonogamous pollination. However, intraflower variation in nectar volume might enhance early departure from the flower or inflorescence, reducing geitonogamy. To examine the adaptive significance of multiple nectar-producing spurs within flowers, we related intraflower variation in nectar characteristics to pollinator foraging behavior and plant reproductive success in protandrous Aquilegia buergeriana var. oxysepala.
We investigated if nectar volume and sugar mass relate to spur length and if intraflower variation in nectar characteristics differ between male- and female-phase flowers. Because male function requires more pollinator visits than female function, male-phase flowers are expected to have greater nectar volume and lower intraflower variation in nectar volume than female-phase flowers. We used intraflower variation in spur length as an indicator of variation in nectar characteristics and investigated how spur length variation affects pollinator behavior, pollen removal, and seed production.
Male-phase flowers had greater nectar volume and lower intraflower variation in nectar volume than female-phase flowers. Intraflower variation in spur length reduced the duration of bumblebee visits. Short visits reduced seed production, but increased pollen removal.
Our results suggest that high intraflower variation in nectar production rate can reduce geitonogamy and potentially increase the genetic diversity of pollen received. Such pattern of nectar secretion within and among flowers may allow flowers to ensure effective pollen transfer or high seed production.
分泌大量花蜜的植物吸引了许多传粉者来访，这可能导致高频的同株异花授粉。然而，花朵内花蜜量的变化可能会促使传粉者更早地离开花朵或花序，从而减少同株异花授粉。为了研究花朵内多个产蜜spur 之间的适应意义，我们将花蜜特征的花朵内变化与Aquilegia buergeriana var. oxysepala 的 protandrous 中传粉者觅食行为和植物繁殖成功率联系起来。
我们研究了花蜜体积和糖质量是否与 spur 长度有关，以及花蜜特征的花朵内变化是否在雄花和雌花之间存在差异。由于雄花功能比雌花功能需要更多的传粉者访问，因此预期雄花的花蜜体积更大，花蜜体积的花朵内变化比雌花小。我们使用 spur 长度的花朵内变化作为花蜜特征变化的指标，并研究了 spur 长度变化如何影响传粉者行为、花粉去除和种子生产。
雄花的花蜜体积大于雌花，花蜜体积的花朵内变化也小于雌花。spur 长度的花朵内变化减少了熊蜂的访问时间。短暂的访问减少了种子的产量，但增加了花粉的去除。
我们的结果表明，花蜜产生率的高花朵内变化可以减少同株异花授粉，并可能增加接收花粉的遗传多样性。这种花蜜分泌在花朵内和花朵间的模式可能使花朵能够确保有效的花粉传递或高种子产量。
