Last week, I mentioned there are many adaptations that have evolved to ensure cross-pollination of flowers takes place successfully so they can produce viable seeds.
Most of the adaptations are in the form of changes to the morphology of the flower that require the pollinator to work at finding the rewards (pollen and nectar) and in doing so, deposit the correct type of pollen onto the female stigma and pick up pollen from the male anthers.
As children, we always competed to see who could find a special type of European orchid called the “bee orchid” (Ophrys apifera). The flower evolved to have striped patterns and colours like those found in some bees.
It is a wonderful example of sexual deception since male bees with raging hormones think the orchid flower is a female bee and try to copulate with it. In doing so, the bees pick up pollen.
Even though a bee eventually clues in it has been deceived, its urges are so strong that it will go off and try again with another bee orchid, hence transferring the pollen from one plant to another.
Other examples are not as complex and specialized. Bees, especially bumblebees, require a landing pad that is strong enough to support their weight. Larger flowers such as delphiniums and snapdragons do provide landing pads, but other flowers do not.
One I love is the tiny blue flower of Cusick’s Veronica. Blue flowers tend to attract bees, but this flower is so small, it is hard for the bee to hang on.
However, the flower has two large stamens (the male parts) - one on either side. The bee approaches, grabs hold of the stamens for stability, pulls them inward and deposits pollen on its stomach. When the bee goes to the next flower in search of the nectar its stomach hits the protruding central stigma, deposits pollen, some of which is from Veronica flowers on the other plants. Voila – cross pollination.
Last week, I showed a photo of lupine flowers. Some of the flowers had the stigmas sticking out from the boat-shaped lower petals (the keel). This happens because the bee had visited, landed on the keel and forced the stigma out like a piston from where it was hidden. As the stigma emerges it hits the bee’s belly covered in pollen - some of which is from other lupine plants.
Another fun adaptation can be seen in a bog flower called Kalmia - bog laurel. The flower is bowl- shaped. Each of the male anthers (containing the pollen) is held under tension tucked into a pocket in the middle of a petal. When a heavy pollinator (e.g., a bumble bee) lands on the petal the anther is released like in a catapult and springs forward hitting the insect, depositing pollen on its sides.
