[phys.org]

"A bean plant treated with hydrogen sulfide (top) is substantially bigger at two weeks after gestation than the control plant (bottom) that was untreated. Credit: Frederick Dooley/University of Washington Hydrogen sulfide, the pungent stuff often referred to as sewer gas, is a deadly substance implicated in several mass extinctions, including one at the end of the Permian period 251 million years ago that wiped out more than three-quarters of all species on Earth."

"At high concentrations – levels of 30 to 100 parts per million in water – hydrogen sulfide can be lethal to humans. At one part per million it emits a telltale rotten-egg smell. Dooley used a concentration of 1 part per billion or less to water seeds of peas, beans and wheat on a weekly basis. Treating the seeds less often reduced the effect, and watering more often typically killed them. With wheat, all the seeds germinated in one to two days instead of four or five, and with peas and beans the typical 40 percent rate of germination rose to 60 to 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."