Unlike lovelorn humans, ground-bound plants can't go searching for a partner; instead, they rely on the wind—or pollinators such as bees—to transfer pollen from one flower to another. But if pollinators haven't paid a visit, many plants can self-fertilize. Now, researchers have discovered a new way this “self-love” happens, and it's rather graceful.
Erysimum incanum is a demure variety of wallflower that grows in the scrublands of Spain and northwest Africa. While studying its millimeterwide flowers in the lab, researchers noticed slow gyrations of its anthers, the pollen-bearing ends of tiny stalks, as the flower opened. Sometimes, the anthers rubbed their pollen directly onto the stigma, the central structure that contains the ovary. On other occasions, the anthers rubbed against each other, causing pollen to fall off and land on the stigma. Researchers photographed the dance (sped up, above) and compared the flower with other species, such as the purple flower with stationary anthers at the end of the video above.
Seeds from the self-fertilization grew into healthy plants without any inbreeding problems, the researchers report online in The American Naturalist. Another sign the reproductive strategy pays off: Self-fertilized plants produced just as many seeds as plants that were hand-fertilized with pollen from other plants.
The shy wallflower joins the ranks of many other plants that self-fertilize. But it takes different strokes for different folks: Often, this lonely pollination happens simply when flowers close and the anthers touch the stigma. What's uncommon about Erysimum incanum is that the self-fertilization occurs while the flower is opening. The new move would be no surprise to Charles Darwin, who in 1876 suggested that flowers in places with few pollinators would likely engage in self-fertilization. And that seems to be the case with Erysimum incanum: Pollinate your rosebuds while ye may.