mangroves. The roots of these plants grow outside the soil for air, as air cannot penetrate this clayey soil. Examples of such plants are papyrus and cattails.

Aquatic plants

Aquatic plants grow in water. Some aquatic plants float on the surface of water, whereas others grow under the water. Accordingly, the aquatic plants are further categorised into three types – floating, fixed and underwater plants.

1. Floating plants: As the name suggests, floating plants float on water. They are light in weight with smaller sizes. Such plants help in protecting small water animals from the direct heat of the Sun. Examples include, water lettuce, duckweed and water hyacinth.

2. Fixed plants: These plants remain fixed to the water bed, for example, water lily and lotus. These plants have hollow and light stem, letting the leaves and flowers float on the water surface. Such floating leaves act as a nesting place for small birds.

3. Underwater plants: These plants are completely submerged in the water. Such plants have narrow, long and ribbon-like leaves. These plants remove the carbon dioxide exhaled by aquatic animals through photosynthesis, thereby help clean the water. Examples of such plants include tape grass, pondweed and hydrilla.