Sewer Gas Accelerates Plant Growth, Development
April 18, 2013

Sewer Gas Accelerates Plant Growth, Development

Brett Smith for — Your Universe Online

Hydrogen sulfide, known to many as ℠sewer gas,´ is a deadly substance that many evolutionary biologists blame for several mass extinction events throughout Earth´s history.

However, according to a new study in the open access journal PLOS ONE, very low doses of the pungent compound spur plant growth.

The study´s lead researcher Frank Dooley, a University of Washington doctoral student, said he stumbled upon the beneficial effect completely by accident.

“We found some very interesting things, including that at the very lowest levels plant health improves. But that´s not what we were looking for,” Dooley said.

The scientist said he had intended to investigate hydrogen sulfide´s toxic effects, but incorrectly used only one-tenth of his planned dosage.

Dooley said he didn´t believe the beneficial results produced by the smaller dosage, so he repeated the test several times and saw the same result produced.

“Everything else that´s ever been done on plants was looking at hydrogen sulfide in high concentrations,” he said.

Hydrogen sulfide is lethal to humans at levels of 30 to 100 parts per million when in water. At a concentration of one part per million — it emits a signature rotten-egg odor.

To return beneficial results, Dooley and his fellow researchers used a concentration of one part per billion or less to water seeds of peas, beans and wheat on a weekly basis, according to the report.  The team also found watering the seeds less often reduced the effect, while watering them more often killed the plants.

For the wheat plants, researchers observed the seeds germinating in one to two days instead of four or five. For peas and beans, the average rate of germination rose from 40 to between 60 and 70 percent.

“They germinate faster and they produce roots and leaves faster. Basically what we´ve done is accelerate the entire plant process,” he said.

Throughout the course of Earth´s history, hydrogen sulfide may have resulted in several mass extinction events, including one about 250 million years ago that is thought to have wiped out over three-quarters of all species on Earth.

Scientists have theorized the deadly gas was most likely produced when sulfates in the oceans were released by the decomposing action of sulfur bacteria.

According to Dooley´s advisor Peter Ward, a UW professor of biology, the rapid plant growth brought on by small concentrations of hydrogen sulfide could be the result of a genetic mechanism that allowed plants to survive these mass extinction events.

“Mass extinctions kill a lot of stuff, but here´s a legacy that promotes life,” Ward said.

Ward said larger plants would have had a better chance at survival, so it makes sense that small dose of the deadly compound would spur growth.

The scientists said they were particularly excited about what the findings could mean for producing algae and other stock that make biofuels.

When plants typically grow larger, they do so by elongating their existing cells. However, the researchers found the hydrogen sulfide treatments resulted in smaller and larger numbers of cells, meaning these plants contain more biomass for fuel production.

“If you look at a slide of the cells under a microscope, anyone can understand it. It is that big of a difference,” Dooley said.