The biggest benefit for the plants is the transference of oxygen to the zone of the root. Stems, roots and rizomas allow transport of oxygen of way more deep of what diffusion would arrive of course through only more important in lands humid of flow superficial is that the submerged portions if degrade and if they transform into remaining portions of vegetation, that serve as substratum for the growth of the microbiano film, responsible for great part of the treatment that occurs, therefore add population of microorganisms, that for biological, chemical and physical processes treat residuary waters. The vegetables stabilize the substratum and limit the canalization of the flow, take carbon, nutrients and incorporate fabrics of the plant, transfer the gases, oxigena the other space inside of the substratum. The species comumente used is the Typhas sp (taboa) – she is proper for the use in wetlands therefore has in its internal structure the fabric formation that contains opened spaces, through which pass oxygen of the atmosphere for leves and for the roots and rizomas being that it has left of the oxygen it can there leave the system to radicular for the rizosfera being created a propitious environment to the aerobic decomposition of organic substance, the rush and taboa is vascular plants, that remove oxygen of air and transfer to the roots. It is had, then, aerobic and anaerobic micron-environments that favor reactions (nitrificao-desnitrificao) that many times reduce the amount of nitrognio’ ‘ , it explains Roston, 1994. 1.3Os microrganismos in wetland a basic characteristic of humid lands is that its functions mainly are regulated by the microorganisms and its metabolism. The microorganisms include bacterium, leavenings, fungos and protozorios, this microbiana biomass consumes great part of carbon many nutrients. It can eliminate nitrogen in these systems by means of nitrificao/desnitrificao processes and posterior gas release in the atmosphere..