Adventitious roots develop from the basal parts of the shoot  and the tap root and become visible above the water line or anaerobic soil.This araerobic pathway provides the vital oxygen needed not only to sustain tap root function  but carry several aerobic mechanisms. This internal aeration is facilitated by the main tissue of  adventitious roots- arenchyma, whose large , gas-filled spaces provide a pathway for the intake of oxygen and the diffusion of useless or deleterious gases. This internal  aeration pathway also reoxidizes the first thin layer in the otherwise anaerobic soil, resulting in the immobilization of metal ions which become toxic in their chemically reduced and insoluble form (Blom 1994). Adventitious roots are responsible for the activation of a key nutritional pathway by which ammonia nitrogen is converted to usable nitrate ( nitrification). Because of  the activation of this alternative chemical/metabolic pathway, plant and tree survival in flooded conditions is possible.