Institute of Evolution and Ecology, School of Life Sciences, Central China Normal University, Wuhan, China.
Department of Biology, Washington University, Saint Louis, United States.
Elife. 2022 Oct 11;11:e81449. doi: 10.7554/eLife.81449.
Animal-pollinated plants have to get pollen to a conspecific stigma while protecting it from getting eaten. Touch-sensitive stamens, which are found in hundreds of flowering plants, are thought to function in enhancing pollen export and reducing its loss, but experimental tests are scarce. Stamens of and are inserted between paired nectar glands and when touched by an insect's tongue rapidly snap forward so that their valvate anthers press pollen on the insect's tongue or face. We immobilized the stamens in otherwise unmodified flowers and studied pollen transfer in the field and under enclosed conditions. On flowers with immobilized stamens, the most common bee visitor stayed up to 3.6× longer, yet removed 1.3× fewer pollen grains and deposited 2.1× fewer grains on stigmas per visit. Self-pollen from a single stamen hitting the stigma amounted to 6% of the grains received from single bee visits. Bees discarded pollen passively placed on their bodies, likely because of its berberine content; nectar has no berberine. Syrphid flies fed on both nectar and pollen, taking more when stamens were immobilized. Pollen-tracking experiments in two species showed that mobile-stamen-flowers donate pollen to many more recipients. These results demonstrate another mechanism by which plants simultaneously meter out their pollen and reduce pollen theft.
传粉动物必须将花粉传递到同种植物的柱头上，同时防止花粉被吃掉。触感灵敏的雄蕊存在于数百种开花植物中，被认为可以增强花粉的输出并减少其损失，但实验测试却很少。 和 的雄蕊插入成对的蜜腺之间，当被昆虫的舌头触碰时，它们会迅速向前弹开，使瓣膜状的花药将花粉压在昆虫的舌头上或脸上。我们将雄蕊固定在其他未修饰的花朵中，并在野外和封闭条件下研究花粉传递。在固定雄蕊的花朵上，最常见的访花蜜蜂停留的时间延长了 3.6 倍，但每次访问采集的花粉粒减少了 1.3 倍，在柱头上沉积的花粉粒减少了 2.1 倍。来自单一雄蕊的自花粉量相当于从单个蜜蜂访问中接收的花粉量的 6%。蜜蜂可能会因为花粉中含有黄连素而被动地丢弃放在身上的花粉，而花蜜中则没有黄连素。食蚜蝇既吃花蜜也吃花粉，当雄蕊被固定时，它们吃的花粉更多。在两种 物种中的花粉跟踪实验表明，具有活动雄蕊的花朵将花粉捐赠给了更多的接受者。这些结果表明，植物还有另一种机制来控制花粉的输出并减少花粉盗窃。
