What are adaptations ? Describe the various adaptations plants to aquatic environment.

Explanation

The plants which remain permanently immersed in water are called hydrophytes. They may be submerged or partially submerged and have the following adaptation :-
(i) They have the presence of aerenchyma (large air spaces) in the leaves and petioles which help to transport oxygen produced during photosynthesis and permit its free diffusion to other parts including roots located in anaerobic soil. This tissue also provides buoyancy to the plants.
(ii) Eichhornia (water hyacinth) has the presence of inflated petioles which keep the plants floating on the surface of water.
(iii) Roots are poorly developed or absent in free floating hydrophytes like Wolffia, Salvinia and Ceratophyllum.
(iv) Various emergent hydrophytes (having leaves projecting above water surface) have a continuous system of air passage which helps the submerged plant organs to exchange gases from the atmosphere through the stomata in the emergent organs.