Air Pollution Affects Pollination Of Night Blooming Flowers, Study Says

Air pollution may mask the distinctive aromas of some night-blooming flowers and risking pollination.

Air Pollution

When the aroma of a pale evening primrose comes into contact with specific contaminants in the night air, crucial scent molecules are destroyed, according to research published in Science.

As a result, moths and other nocturnal pollinators may have difficulty detecting the aroma and navigating to the blossom.

Jeff Riffell, a University of Washington biologist, and his colleagues analyzed hawk moths, which utilize antennae to detect the aroma of flowers from more than a kilometer away.

When they reach an area of wildflowers, the moths beat their wings so fast that they hang in midair and suck nectar, making them mistaken for hummingbirds.

One of their favorites is the delicate evening primrose, a ghostly white flower that blooms at night.

The research team collected the blossoms in an eastern Washington field to sample their aroma. In the lab, scientists identified the individual molecules that comprised the bouquet.

Pollution, however, has the potential to interfere with that extraordinary sense of smell.

The scientists discovered that particular fragrance molecules that moths find appealing deteriorate in the presence of NO3, a strong pollutant produced by vehicles, coal, and other industrial emissions.

NO3 accumulates in the atmosphere at night because it is eliminated by sunlight.

In lab trials, two moth species, the white-lined sphinx and the tobacco hawk moth, failed to fly to the primrose fragrance when exposed to NO3 levels commonly found at night in towns.

When the researchers returned to the field and treated the aroma of both real and odor-emitting artificial flowers with NO3, wild moth visitation decreased by almost 70%.

"It was surprising [that] a seemingly subtle change in concentration of only two compounds - out of more than 20 - was sufficient to eliminate the flower's attractiveness," Riffell says.

Change In Plant Community

The researchers noted that flowers only bloom once per night, and without their pollinators, a huge change in the plant community might occur.

To test the findings in nature, ecologist Jeremy Chan, now at the University of Naples Federico II in Italy, planted a field of actual and imitation primroses.

280 kilometers east of Seattle. Some fakes emitted lab-made primrose.

Others emitted both the aroma and compounds that react in the air to produce nitrate radicals. Cameras counted the number of times moths visited the experimental buds.

Moths typically visited genuine and synthetic flowers that emitted an unblemished primrose aroma two to three times every night. The team discovered that imitation flowers with contaminated scents received less than one nightly visit on average.

The study is the "first in this area" to examine the impact of nocturnal pollution on pollinators. Experts said seeing the outcomes was both exciting and worrisome.

Jose Fuentes, an atmospheric scientist at Penn State said scientists need to study how the observed insect behavior can affect foraging.

If insects become more confused in places as air pollution worsens, "it will impact pollination, crop productions [and] the health of native plant species," he added.