Other oxygen requiring organisms in the soil surrounding the roots are killed. These organisms normally help recycle elements for trees. The tree can develop many nutritional problems after floods. Oxygen is available through lenticel and stomate openings, and can move for short distances in both wood and bark. Flooded trees produce larger, more open lenticels which are connected to intercellular spaces and can provide more oxygen transport.
Some trees use vertical air roots to assist with oxygenation.
One growth response of trees to flooding is production of proportionally greater numbers of thin-walled cells called parenchyma. This cell type is found in both the xylem and phloem. Resin duct numbers are also increased in species with these features. Flooding initiates production of low density cells and more intercellular spaces in the xylem, phloem and bark to facilitate oxygen transport and removal of toxic materials. This tissue forms by cells dissolving and cell walls separating to form a spongy mass of cells with large air spaces.