Nature does not waste energy

  • Birch pollen takes to the air. Harald Olsen/NTNU

Wednesday, June 06, 2018

I’ve been thinking about pollen lately — for two reasons. First, in honor of pollinators and National Pollinator Week upcoming, I’m giving a slideshow-talk on the amazing world of pollinators and plants. Wednesday, June 20, 6:30 p.m. at the Peterborough Town House, hosted by the Peterborough Open Space Committee.

It’s often said that one out of three bites we eat comes from plants that need to be pollinated. Nuts, fruits, vegetables, as well as drinks, fiber and medicines.

That’s the human-centered focus. For the wild ones, a diversity of plants — pollinated plants — provides essential food and shelter. As a teaser, certain plants have evolved size, shape and color to lure in certain pollinators who have evolved to better extract pollen and nectar from those plants. One can’t live without the other. Once pollinated, a plant shuts off its nectar supply. Mission accomplished. And the pollinator moves on to other plants in need of pollination.

Nature does not waste energy.

We’ll talk about the true worker bee pollinators, their decline, and what we can do about it.

Second: Pollen is in the air, borne by wind not insects.

Time outdoors these days gets me coughing. It’s tempting to think: Pine pollen. Hot, windy June days bring visible clouds of pollen emerging from stands of white pine. I mentioned the cough to son-in-law Chris as he and grandchildren Rhys and Hayden were weeding our backyard raspberry patch. His family is midway through a no-shopping year. Weeding the patch was their birthday present to Carl. (I intend to drop hints that our garage needs cleaning and organizing come my August birthday. Theirs is a marvel.)

As soon as I mentioned the coughing, Chris started coughing. Quick research finds that only 10-20 percent of us go into a histamine-releasing reaction to pollen in the air. It’s a long-ago evolved antibody reaction to parasites. The wheezing, watery eyes and mucous expulsion is intended to repel a perceived invader. Or so I read.

About pollen, it’s the equivalent of male sperm that needs to be delivered to female receptor for seed production to occur — and with it continuation of the species.

Most trees at our northern latitudes are wind pollinated. It makes sense, somewhat. They’re high, producing pollen in the canopy where winds can disperse tiny pollen grains.

All grasses are wind pollinated. The grass family is a large one, all the named grasses and grains, too: corn, barley, wheat and the like. “Hay fever” applies to a lot of plant species.

Wind pollination makes sense for grasses, too, as they grow low and close together. Wind blows pollen from one plant to another to achieve cross-pollination.

Cross-pollination makes for bigger, better, more offspring than self-pollination. Trees have strategies to promote cross-pollination. In pines, light-green female flowers grow higher on a tree that brownish pollen producing male flowers, decreasing chances that pollen dispersed from lower down will reach female flowers higher on the same tree. Some tree species including maples have separate male trees and female trees as their strategy to avoid self-pollination. Adding interest, some maples come in all forms: male, female, and bisexual, and sometimes they change sex.

There is a lot going on out there.

Whether canopy trees or ground-level grasses, wind pollination is an inefficient means of delivery compared to a lumbering bumble bee coated in pollen going from one flower to another, pollinating as she goes. This inefficiency explains visible clouds of pine pollen; pollen on windshields, windowsills, pooled in puddle edges or along shorelines. The more pollen the greater chances it reaches its intended target. To give a sense of pollen overproduction, one grass flower-head produces many million pollen grains. Given that nature tends not to waste energy, I haven't figured out the strategy as pollen overproduction requires great energy expenditure.

Pine pollen is large, but most tree and grass pollen is invisible to our eyes. That's the pollen small enough to infiltrate nose, mouth and eyes to create allergic reactions. Blame oaks and other trees with tiny pollen grains, but not pines.

Which leaves the scratchy-throat cough a mystery. It's not a histamine rising to defend son-in-law Chris and me against invading parasites. Whatever its cause, it's far preferable than wheezing, coughing and itchy eyes that the 10-20 percent endure. No complaints; just curiosity.