Roots obtain oxygen from air in the soil for respiration. In the absence or deficiency of O2 , root growth is restricted or completely stopped. How do the plants growing in marsh lands or swamps obtain their O2 required for root respiration?


The roots of the plants (e.g., Rhizophora) growing in marshy/swamp areas become negatively geotropic. They grow vertically upwards in air, above the soil level and respire so called respiratory roots or pneumatophores.