Carolina Environmental Diversity Explorations
Wetlands of the coastal plains · By Dirk Frankenberg
The “knees” of cypress
Figure 10. Cypress trees use these “knees” to breathe. (Photograph by the author. More about the photograph)
The other major adaptations of cypress and gums to flooded soils is their characteristic root extensions called “knees” shown in Figures 10 and 11. These structures are gas exchange systems within which oxygen from the air is conducted along the roots that live in the anaerobic (no oxygen) soils of the swamp floor. Recent studies have shown that in cypress trees about 17 percent of the roots’ oxygen demand is met by gas exchange through the tips of the knees.
