Pine Pollen Profusion The greenish yellow dust was all over my front porch, the top of my car, and every other outdoor surface. My small grove of white pines had decided that this was a year to produce an extraordinary amount of pollen. The tips of the lower branches of these trees were densely covered with the tiny (1/2 inch long) male cones whose only job is to produce pollen. These small male cones last for only a few weeks until they can produce and release pollen. The cones are so small that botanists call them micro-­‐
strobili (my-­‐crow-­‐stroh-­‐bih-­‐lie). A pollen grain begins its short but complicated life inside these short-­‐lived male cones. The male cones first task is to produce spores. Unlike other parts of the plant, a spore carries only half the genetic material needed to produce a fertile seed. The spores sprout inside the male cone and develop quickly into a multicellular pollen grain. When these pollen grains are mature the male cone opens and releases huge numbers of pollen grains. Pine pollen is windblown and it can travel many miles from the parent tree carrying genetic material to the larger female cones appropriately called macrostrobili (mack-­‐row-­‐ stroh-­‐bih-­‐lie). The pollen grain is covered by a tough outer coat to protect it during its airborne travel. If a pollen grain does not land on a female cone, its tough coat may persist for centuries in the soil or in sediments in the bottom of ponds and lakes. It is possible to determine what species lived in an area long ago by examining these buried pollen grains. Pine pollen grains also have two air filled extensions that function a little like balloons to keep the pollen grain afloat on the air currents. Pine trees can each produce an enormous number of pollen grains, but very few of the pollen grains will find their way to a fertile female cone. Apparently enough pollen grains are successful at reaching their intended target because pine trees continue to produce viable seeds and replace themselves in natural ecosystems around the world. When the pollen grain arrives at a female cone the pollen grain sprouts producing a pollen tube that extends into the female counterpart that is called an ovule. Inside the ovule the development continues and sperm are produced. Since the sperm are already where they need to be, thanks to the growth of the pollen tube, they do not need to swim. The sperm will then unite with the ovule and with this combined genetic material the new structure, a zygote, can develop into a seed while still inside the female cone. The female cones, much less abundant, are found near the tops of the trees. This location makes it less likely that a single tree will pollinate itself. Does pine pollen cause human allergies? According to the American College of Asthma, Allergy and Immunology, allergic reaction to white pine pollen are rare. But among those rare cases, come can be serious. Grasses and other plants that release pollen in the spring time seem to cause much of the hay fever like symptoms that many people suffer in the spring. Pine pollen was used medicinally in ancient Chinese culture where it was thought to boost energy. Today it is sold as an herbal supplement, but there are few scientific studies validating its effectiveness. Fortunately the pine pollen season is rather short, lasting only a few weeks. Unfortunately for humans, pines produce a huge amount of pollen. In any case the long-­‐term benefits of trees far outweigh the short term inconvenience of pollen grains. So I washed my porch and my car and marveled at the successful intricacies of nature. PHOTO: Clusters of male cones releasing copious amounts of pollen in an Alliance, OH backyard in mid May. These white pine trees each had thousands of male cones this spring. Photo by C.McClaugherty