Question

Pneumatophore is present in-
A) Rhizophora
B) Cholobranchia
C) Pistea
D) None of the above

Answer 1

Pneumatophores are aerial roots, they are present in plants present in marshy areas or in mangroves. The roots grow in an anti-gravitational manner.

Complete Answer:
Some plants which grow in swampy areas or marshy areas or in salt waters, many roots of the tree grow vertically upwards, above the ground. Such roots are called pneumatophores. Dissolved oxygen is absorbed by roots from the soil. However, in anaerobic soils, it becomes impossible to process gaseous exchange through soil, here pneumatophores come into action as they can absorb oxygen directly from air and respiration can occur. They are also known as air root. These specialized roots help the plants to breathe air in waterlogged or muddy habitats. The roots may either grow from the stem in downward direction or upward from typical roots. If these roots come up from soil, several botanists call them aerating roots rather than aerial roots. Lenticels cover the surface of these roots. The lenticels take up air into spongy tissue from where oxygen is supplied throughout the plant, wherever it is needed using osmotic pathways. Black mangrove and Grey mangrove are differentiated by the presence of pneumatophores from other mangrove species. Pneumatophore is not found in Pistea and Cholobranchia but is present in rhizophora.

Hence the correct answer is option ‘A’.

Note: Pneumatophores are modification of stem. Due to the swampy environment, supply of oxygen gets restricted, pneumatophores arise to increase oxygen uptake for respiration. Cypress knees are also modified roots projected upward from their roots which were initially thought to have functions like pneumatophores, but according to recent studies, this hypothesis was neglected.