Nothing to Sneeze At
Gray Stanback
It’s spring, which for many of us here in Davidson means the return of flowers, birds, butterflies, and other pleasant things. However, it also means the return of something generally considered to be unpleasant—pollen. Pollen, be it from trees, from ragweed, or from flowers in general, is one of the leading causes of allergies. Needless to say, this is one of the least enjoyable aspects of Spring.
However, pollen also plays an important role in nature. You might not be able to understand this while that pollen is dusting your porch or caking the windshield of your car, but it is part of how plants reproduce.
There are two basic strategies for reproduction, if you’re a plant. One is to produce enormous amounts of pollen, disperse it far and wide, and let it find another plant purely by chance. The other is to produce very little pollen but take special measures—such as by attracting pollinators—to ensure that as much of that pollen as possible reaches another plant. Most plants that fall into the former group rely on the wind to carry their pollen from place to place, while those that fall in the latter group rely on animals.
Animal-pollinated plants are usually pollinated by bees, butterflies, hummingbirds, and various other animals that feed on nectar. The pollen that people are often allergic to, on the other hand, comes from plants that are pollinated by the wind. Wind-pollinated flowers are different in structure from insect-pollinated ones. The most obvious difference is that they lack both petals and nectar. In fact, if you’ve seen the yellow, grainy “catkins” of a pine tree on the ground, those are actually its flowers. The pollen is produced in large quantities and broadcast into the air, where it can trigger an allergic reaction if inhaled.
Other differences involve the structures of the pollen grains themselves. Animal-pollinated plants have sticky or spiky pollen grains, which allow them to stick to pollinators. Wind-pollinated plants, on the other hand, have much smaller pollen grains that are lightweight and rounder, making them aerodynamic enough to be blown about in the wind.
The flowers themselves are also different. As mentioned before, the flowers of plants that are pollinated by animals have conspicuous petals and produce nectar as a lure for their pollinators. However, they also have smaller stigmas—that is, a part of the flower located inside it to serve as a pollen receptacle. In wind-flowering plants, the stigma is long and net-like so as to catch the pollen out of the air.
Whether wind-pollinated or animal-pollinated flowers are an indispensable part of our ecology, and are a globally recognized symbol of spring. So one day, when the weather is nice, take a walk outside and take a good look at some. Just try not to breathe in too much pollen!