Roots obtain oxygen from the 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?
In some plants such as Rhizophora growing in swampy areas, many roots come out of the ground and grow vertically upwards. Such roots, called pneumatophores, help to get oxygen for respiration.