Question

Collect some aquatic plants- cut the leaves and stems. Observe them under microscope and record your observations like air presence / absence of air spaces etc., and answer the below.
a) Why do they float on water?
b) What make them float?
c) Are there any other reasons for their floating?
d) Draw a diagram of what you have observed under microscope?

Answer 1

1. The leaves and stems of aquatic plants are found floating on the water surface for the process of gaseous exchange. It involves the intake of carbon-di-oxide and release of oxygen.

2. In aquatic plants, large air cavities are present in parenchyma to give buoyancy to the plants to help them to float. Such parenchyma type is called are aerenchyma.

3. When optimum sunlight is not present beneath the water surface, the leaves come up to the surface to carry out the process of photosynthesis efficiently.

4. The microscopic diagram of aerenchyma is drawn above.