The wild carrot and its evolutionary “trick”
This morning, while walking near the hospital in Ciudad Real (Spain), I photographed these beautiful specimens of Daucus carota (there are many subspecies, but it’s not necessary to get specific) or, in other words, wild carrots. There were specimens everywhere, and here are a few I happened to come across, right at the edge of the sidewalk.
The thing is, this plant has a certain feature that has always caught my eye. If you look at the center of the cluster of small flowers, you’ll see a darker central flower (which is actually usually made up of several small flowers pigmented with anthocyanins, although we typically perceive them as a single striking “bud”); it can be black, dark, or reddish. You can see it in more detail here.
Wild carrots display that striking dark or colorful “bud” to attract insects, or at least that is what has traditionally been said. In one of the photographs, you can see an immature or transitional specimen, displaying the characteristic pink hues before the umbel fully opens and turns white.
But let’s get to the curious part: the striking central flower, which is usually sterile. Its possible function has long been a subject of debate. Obviously, it is a structure resulting from an evolutionary process, but its purpose is not entirely clear. It has been suggested that it might have an adaptive function to mimic insects (although some studies support this idea, others suggest that its effect depends on the local ecological context), which may deter potential herbivores and attract pollinating insects. This “attractive” function would act as a kind of lure capable of indicating the presence of food, a good place to land, or opportunities for mating.
By the way, Daucus carota bears a certain resemblance to hemlock, which is poisonous, and its leaves can also cause skin irritation in some people upon contact, so it’s best to look but not touch — or to do so with caution. Handling this type of plant is relevant, for example, in the classic experiment with white flowers in colored water. It works well with wild carrots because their flower “head” is a large white umbel made up of hundreds of very small florets. That light-colored surface makes the dye visible, just as it does with white carnations. This is not a “biological” color change, because the plant does not create new pigments or “choose” the color. What happens is a simple passive staining of the flower tissue. The soluble dye rises with the water through the xylem, reaches the flowers, and the water evaporates through transpiration, leaving part of the dye accumulated in the small flowers.
In the case of Daucus carota, the effect is most visible on the “head” because there is a large, thin, white surface there that is prone to evaporation. The stem also carries colored water, but the effect isn’t as noticeable because it’s green and more opaque. If you cut the stem crosswise after several hours, you can see colored spots or rings corresponding to the vascular bundles. Oh, in the experiment, the dark central bud usually won’t change much, because it already contains natural dark pigments, so a red, blue, or green dye will be masked.
