In order to carry on respiration, plant cells need oxygen and a means of disposing of carbon dioxide just as animal cells do. Unlike animals, plants have no specialized organs for gas exchange (with the few inevitable exceptions!). Each part of the plant such as leaves, stems and roots perform their own respiration. In plants respiration takes place at much slower rate as compared to animals. Also, there is very less transportation of respiratory gases from one part of the plant to another.
Respiration in leaves
In leaves the exchange of respiratory gases takes place through very small pores called stomata (singular stoma). The stomata are present in large number on the lower surface of leaves of plant. Each stoma has a pore at its centre which is surrounded and controlled by two kidney shaped cells called guard cells. When the stoma opens the exchange of gases takes place between the atmosphere and interior of the leaf by the process of diffusion.
Respiration in stems
In the plants having hard and woody stems and mature roots the exchange of gases takes place through lenticels. Lenticels are actually loosely packed dead cells which are present as small pores on the bark of woody plants or old roots. These enable oxygen to reach the intercellular spaces of the interior tissues and carbon dioxide to be released to the atmosphere by the process of diffusion.
Respiration in roots
In plants respiration also takes place through roots. In soil oxygenated air is present in air spaces between soil particles. This oxygen is absorbed into the roots by root hair present on the roots. In fact, a root hair is a lateral tubular outgrowth of the outer epidermal cells of a root. The oxygen present in between the soil particles diffuse into the root hairs. From root hairs, oxygen is supplied to all the parts of roots for respiration. During respiration, oxygen is converted into carbon dioxide gas which is diffused out of the roots by the same root hairs.
Test Your Understanding and Answer These Questions:
- Explain respiration in plants.
- Write a brief note on stomata.
- What are stomata and lenticels? What is their role in respiration?
- Which part of roots is involved in exchange of respiratory gases?