We will discuss about the plants living
in water. Plants growing in water are called aquatic plants. There are three
types of aquatic plants. They are: (i) Floating plants, (ii) Fixed plants, (iii)
Under water plants. There are
some plants which float on water. Some plants like duckweed,
green-alge, wolfia, water-hyacinth and
pistia are some of the floating plants that float freely on top of the water. They are called floating plants. They have spongy bodies.
Like a sponge there
are lots of empty spaces throughout their body and are filled with air. This
makes the plants light enough to float. Some plants
like water-lily and lotus have roots that fix the plants in the mud at the
bottom of the pond. They are known as fixed aquatic plants. Roots of such
plants are fixed in the soil at the bottom of a pond. They have plate-like
leaves that float over the surface of water. The stomata in the leaves are on
the upper side.
The stems are hollow and very light. This helps the leaves to
float. The stems are very flexible. They bend with the flow of water so they do
not get damaged by strong current. Some
plants like pondweed, tape-grass, hydrilla, etc. are some common plants which live
and grow under water completely. They are called underwater or submerged plants. Their roots fix them in the muddy soil. These plants have narrow, thin leaves
without pores. These plants move along with the current.
Such plants have very
delicate shoots. They breathe through their body surface. The stems are
flexible and have air spaces. We can grow such plants in aquarium.
Adequate sunlight is also hard to come by for submerged plant species. The amount of light energy absorbed by an underwater plant is less than the energy that is available to land plants. Particles in water such as silt, minerals, animal waste and other organic debris reduce the amount of light that enters the water.
Chloroplasts in these plants are often situated on the surface of the leaf to maximize exposure to light. As depth below the surface increases, the amount of sunlight available to aquatic plants decreases. Some plant species have anatomical, cellular or biochemical adaptations that allow them to carry out photosynthesis successfully in deep or murky water despite the decreased availability of sunlight.