|Nectar guides © Beatriz Moisset|
Most flowers want to make it easy for
the visitor to find its way around. Thus, in addition to attracting
pollinators with their colors and aromas, they guide their visitors
in the right direction. This serves two purposes; it facilitates the
task of the pollinator and enables the flower to have its pollen
deposited where it is most needed.
Have you noticed the streaks of color
radiating from the center of many blossoms? These are the nectar
guides that tell the visitor: this is the way to the food. Violets
and lupines are good examples. The variety of violets is amazing. We
can count more than a hundred species and hybrids. Most of them are
native, although a few have been introduced from Europe. As a
footnote, it is worth mentioning that some violet species are the
food plant of fritillary butterflies.
|© Beatriz Moisset |
Don’t you find it rather surprising
that the humble violet is the state flower of four states? It would
be more correct to say violets, plural. Illinois did not attempt to
specify which species, even after giving their flower the name of
purple violet to distinguish it from yellow violets. New Jersey and
Wisconsin chose the Viola sororia and Rhode Island, Viola
palmata. Botanists and horticulturists pay attention to these
things. However, legislators often ignore such details. This doesn't
matter since all violets exemplify the nectar guides vividly.
Illinois: Purple Violet (Viola)
New Jersey: Common Blue Violet
Violet (Viola palmata)
Blue Violet (Viola
A slightly different type of nectar
guides is present in bluebonnets (Lupinus). This Texas state
flower includes all the species of bluebonnet that grow in that
state. The guides become visible only when the flower opens and becomes receptive to pollinators. Bluebonnets belong to the pea family, Fabaceae, which is
valuable to ecosystems because it enriches the soil by fixing
Texas: Texas Bluebonnet (Lupinus
flowers use a different way to guide the pollinator to the desired
place. It is called bull's eye. The color of the flower's center
contrasts with the rest of the blossom. Several state flowers
illustrate variations of this theme. Maryland's black-eyed Susan and
Oklahoma's Indian blanket are fine examples. So are Florida's
tickseed and Kansas' sunflower.
|Sunflower © Beatriz Moisset |
researchers played a trick on visitors to these flowers to test the
hypothesis that the bull's eye helped them find their way. They
methodically pulled out all the petals of flowers of this type and
glued them back in after reversing their position so that the darker
part was in the outside. True enough, bees would land on the blossom,
walk to the edge and stick their tongues out in search of nectar.
They must have been mighty puzzled and annoyed at finding none.
|Indian blanket. © Beatriz Moisset |
flowers, such as coreopsis, apparently lack this contrast. They
appear uniformly yellow to our eyes. But bees see certain colors that
escape us. They can see in the range of ultraviolet light, the
so-called black light. The flowers, in turn, have a pattern that
becomes visible only under this particular kind of light waves. The
flower that appears uniformly yellow to us is seen by a bee as having
a black center surrounded by a light halo.
|Coreopsis. The bull's eye is visible only under ultraviolet light. © Beatriz Moisset |
Florida and Kansas have state flowers with bull's eyes, black-eyed
Susan, tickseed, and sunflower, respectively. Oklahoma is rather
unusual in having not one but three types of flower symbols: the
mistletoe as its floral emblem, the Oklahoma rose as its state flower
and the Indian blanket, as its state wildflower. The latter has a
conspicuous bull's eye.
Black-eyed Susan (Rudbeckia hirta)
(Wildflower): Tickseed (Coreopsis)
Sunflower (Helianthus annuus)
(Wildflower): Indian Blanket (Gaillardia
article is about one of the many ways in which flowers increase the
efficiency of the pollination process. In the next post we'll see
examples of another strategy, frugality.
Black-eyedSusan under ultraviolet light
Anne O. State