Q.5 Describe the process of gaseous exchange in plants.
Answer:
Introduction
Plants have no organs or systems for the exchange of gases with the environment. Every cell of a plant exchanges gases with the environment by its own.
Explanation
i)ย Gaseous exchange in leaves and young stems
The leaves and young stems have stomata in their epidermis for gaseous exchange. The inner cells of leaves (mesophyll) and stems also have air spaces among them which help in the exchange of gases. In young stems and leaves, some gaseous exchange also occurs through cuticle.
Explanation
During the daytime mesophyll cells of leaves carry out photosynthesis and respiration side by side, the oxygen produces in photosynthesis is utilized in cellular respiration. Similarly the carbon dioxide produces during cellular respiration is utilized in photosynthesis. However, during night when there is no photosynthesis occurring, the leaf cells get oxygen from the environment and release carbon dioxide through stomata.
ii. Gaseous exchange in woody stems and mature roots
In woody stems and mature roots, the entire surface is covered by bark which is impervious to gases or water. However, there are certain pores in the layer of bark. These are called the lenticels. The lenticels allow air to pass through them.
iii. Gaseous exchange in young roots
Gases are found in the soil surrounding the roots. These gases diffuse in and out of the general surface of the young roots.
iv. Gaseous exchange in aquatic plants
The aquatic plants get the oxygen dissolved in water and release carbon dioxide in the water.
