Question

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 marshlands or swamps obtain their O2 required for root respiration?

Answer 1

In some plants such as Rhizophora and Sonneratia (mangrove plant) growing in swampy areas near river mouths (saline marshy soil or halophytes), many roots come out of the ground and grow vertically upwards (negatively geotropic: against gravitational force). Such roots, called pneumatophores or breathing roots or respiratory roots, help to get oxygen for respiration.