Question

why are breathing roots found in mangroves only.

Answer 1

It is because an aerial root may be defined as a root which, for part of the day at least, is exposed to the air. The mangrove mud is rather anaerobic (oxygen poor) and unstable and different plants have root adaptations to cope with these conditions.

Answer 2

as to respire respirable roots need as the water in that has salinity and fresh too so to avoid from High concentration of water