formationFlooded conditions result in low oxygen concentrations. Low oxygen concentrations generally stimulate trees and plants to produce ethylene, a plant hormone. Traditionally, researchers have theorized that high ethylene concentrations stimulate the formation of adventitious roots. This claim is unsubstantiated and some research indicates quite the opposite.Researchers  have not elucidated whether ethylene or anaerobic soil conditions is responsible for activating a biochemical pathway that would lead to adventitious root formation. The production of ethylene has been associated with flooded conditions, so the two variables- low oxygen content and ethylene production are often treated as one variable. Futhermore, since adventitious root formation is rapid in flood  tolerant species after the onset of flooding, ( “ within two days  for R. palustris”- Blom et. Al 1994),  one must consider the differing concentrations  of ethylene  during the various stages of flooding. Exogenously applied ethylene over a wide range of application has been  shown to slow elongation of adventitious roots ( Visser et. al 1997). Ethylene has also  been implicated in slowing down primary root elongation and adventitious root formation moreso  than  anaerobic soil conditions . This evidence would lead one to question whether adventitious root formation is promoted by high ethylene concentrations , oxygen depravation, or by a mechanism  whose purpose is to diffuse the accumulation of growth-inhibiting concentrations of ethylene.