The invention discloses a method for separating inner-layer and outer-layer substances of a
wetland plant root surface iron film. The method comprises the following steps: S1, taking roots, shaking off soil, and washing the roots with
sterile water; S2,
cutting the roots into root segments and placing in a
centrifuge tube, adding a PBS-S
phosphate buffer solution, carrying out vortexes, then taking the roots out of the
centrifuge tube, centrifuging the solution and then carrying out
microbial DNA extraction of an outer layer of the
root surface iron film, wherein
solid substances in a suspension in the
centrifuge tube are substances of the outer layer of the
root surface iron film; and S3, putting the roots after the vortexes into another new centrifuge tube, adding 0.5 Mhydroxylamine-0. 5M
hydrogen chloride solution and sterile glass beads into the centrifuge tube, and manually shaking the centrifuge tube up and down for 5 minutes till that the surfaces of the roots become white so asto obtain a
solid substance in a suspension in the centrifuge tube, wherein the
solid substance is a root surface iron film inner-layer substance. In the invention, a circulation process of inner andouter
layers of substances and a change condition of microorganisms can be analyzed so that the influence of an
oxygen concentration gradient on
rhizosphere iron-
sulfur circulation can be better revealed.