Wednesday, May 6, 2015

Pollen makes seeds, but can also make weather

Grains of pollen on flowers or blowing on the Hawaiian tradewinds have many purposes, but perhaps the strangest is in rainmaking.

(Image: Pollen grains. Credit: Eric Grimm, National Climatic Data Center, NOAA.)

Certainly pollen’s primary function is to facilitate the sexual reproduction of plants. It often does that with the help of the winds, or various pollinators like birds and bees. Occasionally, as with the vanilla, pollen must be manually transferred by humans, since the natural pollinator of vanilla orchids is not present in most vanilla-growing areas.

Honeybees use pollen is also a vital food source, for bees are pollen-eaters. The white to yellow to cream-covered grains are collected in sacs on their hind legs and brought back to hives to provide protein and other nutrients that don’t come with the nectar they also collect.

Pollen maddens folks with specific allergies.

But until recently. it has been clear that pollen grains are generally too large to play a role in cloud formation. They drop to the ground—or onto blossoms, too soon. 

New scientific research indicates there’s more to that story.

A paper in the journal Geophysical Research Letters notes that pollen grains break up into smaller pieces. Sometimes merely getting wet can do this—causing the grains to explode into smaller piece. And those pieces can be small enough to form the core of water droplets—cloud condensation nuclei.

 It’s a unique situation in which the biological world interfaces with the meteorological world—and some pundits will doubtless see Gaia-inspired implications in this association.

Living plants, the paper’s authors say, may thus influence climate. An American Geophysical Union press release uses the headline. “Pollen and clouds: April flowers bring May showers?”

“When we were looking in the allergy literature we discovered that it’s pretty well known that pollen can break up into these tiny pieces and trigger an allergic response,” said lead author Allison Steiner, an associate professor of atmospheric, oceanic and space sciences at the University of Michigan.

They did some research and found that “when pollen gets wet, it can rupture very easily in seconds or minutes and make lots of smaller particles that can act as cloud condensation nuclei, or collectors for water,” Steiner said.

There’s a YouTube report on the research here. 

Water droplets in the atmosphere form around all kinds of nuclei. They can be dust particles, bits of human-caused pollution, and now,
we find, bits of busted pollen.

© Jan TenBruggencate 2015

No comments: