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In the 1930s, American artist Georgia O'Keefe wrote: "What is my experience of the flower if it is not color?" O'Keefe is best known for her vibrantly colorful close-ups of petals and stamens on large canvases.
People love flowers for their array of colors, textures, shapes and fragrances. But is pleasing the human eye the purpose of nature's floral design?
Hardly. Survival is the plant's top priority, reminds Claude dePamphilis, a Penn State plant evolutionary biologist and principal investigator of the Floral Genome Project.
"The beauty of the flower is a by-product of what it takes for the plant to attract pollinators," says dePamphilis. "The features that we appreciate are cues to pollinators that there are rewards to be found in the flower."
Scent, color, and size all attract a diversity of pollinators, which include thousands of species of bees, wasps, butterflies, moths, and beetles, as well as vertebrates such as birds and bats.
Flying insects, comprising the vast majority of pollinators, stop at the plant to eat nectar and pick up pollen, which they then distribute as they visit additional flowers. Notes dePamphilis, "Pollinators are providing a very important service to the plant without which it couldn't reproduce."
To aid insects in finding the nectar—and thus, the pollen—many flowering plants have evolved to possess bright colors (hummingbirds and butterflies favor reds and yellows), as well as "nectar guides" that may only be visible in ultraviolet (UV) light—a wavelength of the light spectrum bees can see and people cannot. From a bee's-eye-view, the UV colors and patterns in a flower's petals dramatically announce the flower's stash of nectar and pollen.
The patterns on flowers that both humans and pollinators can see—such as the lines on petals called striations—serve as a sort of air traffic control system for bees, and help guide them into the "bull's-eye" of nectar and pollen at the flower's center, adds dePamphilis. Thanks to this co-evolutionary trait that developed between the two species, the bee can efficiently visit many blossoms and pollinate a larger number of plants.
Some flowers, such as horse chestnuts and sunflowers, change colors within the ultraviolet spectrum throughout their lifespan. As dePamphilis explains, to pollinators these changes are visual signals of an abundance or lack of nectar, blaring "Visit me now!" or "Don't bother!"
To discover more about how these relationships evolved, dePamphilis and colleagues are using DNA-sequencing to dig back into the evolutionary history of flowers. "What we're really trying to do is infer the characteristics in a detailed, genetic way of what the earliest flowering plants were like," dePamphilis explains.
The fossil record dates the first flower somewhere between 125 and 140 million years ago. "How did those first flowers become the thousands of different varieties we now see in nature?" dePamphilis asks. "Gene mapping may shed some light on the beginning of the story."
While most flowers look and smell good to humans, some evolved strategies to attract their pollinators that are downright repellent to us, he notes. Plants belonging to the parasitic genus Rafflesia, native to Indonesia, produce what experts agree is the world's largest single flower, growing up to three feet wide. In addition to its sheer size, a Rafflesia flower announces its presence by its odor—a putrid stench of rotting meat. Though repulsive to us, the odor of "the stinking corpse lily," as the flowering Rafflesia arnoldii is known, proves irresistible to its main pollinators—carrion flies.
One has to wonder what how Georgia O'Keefe, who made art out of pretty flowers and alabaster animal skulls alike, would have painted this unsightly—but unforgettable—blossom.
Claude dePamphilis, Ph.D., is professor of biology in the Eberly College of Science. His e-mail is cwd3@psu.edu.
I'm Claude dePamphilis, a plant evolutionary biologist and the principal investigator of the Floral Genome Project at Penn State. With a deep passion for the intricate world of plant evolution, I've dedicated my career to unraveling the mysteries of floral design and the relationships between plants and their pollinators.
In the article you provided, I discuss the fascinating interplay between flowers and their pollinators, emphasizing that the beauty we appreciate in flowers is a by-product of the plant's evolutionary strategies to attract pollinators. Scent, color, size, and even ultraviolet patterns all play crucial roles in signaling rewards to pollinators such as bees, wasps, butterflies, moths, and even vertebrates like birds and bats.
I highlight the co-evolutionary traits that have developed between flowers and pollinators, such as the intricate patterns on petals serving as an "air traffic control system" for bees. The article delves into the evolutionary history of flowers, with my team and I using DNA sequencing to explore the characteristics of the earliest flowering plants dating back 125 to 140 million years.
Furthermore, I touch upon the intriguing strategies some flowers employ to attract pollinators, even if these strategies may be repellent to humans. For example, I mention the parasitic genus Rafflesia, native to Indonesia, whose flowers emit a putrid odor of rotting meat to attract carrion flies as pollinators.
As an expert in plant evolutionary biology, I strive to understand the complexities of floral design and the mechanisms that drive plant reproduction. If you have any specific questions or if there's a particular aspect of the article you'd like me to elaborate on, feel free to let me know.
