#gaseousexchangeinplants #plants #gasexchange #biology #textbook #igcse

Pg:- 88 to 92

ch:- 6

Gaseous exchange in plants is the process through which they take in carbon dioxide (CO₂) and release oxygen (O₂) and water vapor. This exchange occurs primarily through small openings called stomata, which are located on the surface of leaves, and to a lesser extent through lenticels in stems and roots.

During the Day:

• Photosynthesis is the dominant process.

• Plants absorb CO₂ from the air through the stomata. This gas is used in the chloroplasts to produce glucose using sunlight.

• As a byproduct of photosynthesis, O₂ is released through the stomata.

During the Night:

• Since photosynthesis cannot occur without sunlight, respiration is the main process.

• Plants take in O₂ for respiration, which they use to break down stored food (glucose) for energy.

• CO₂ is released as a byproduct.

Mechanisms of Gaseous Exchange:

1. Stomata:

   • Guard cells control the opening and closing of stomata. When the guard cells are turgid (full of water), the stomata open; when they lose water, the stomata close.

   • This regulation prevents excessive water loss while allowing the exchange of gases.

2. Lenticels:

   • These are tiny pores on the bark of woody plants and stems, enabling gas exchange, especially in areas where stomata are absent.

3. Diffusion:

   • Gases move in and out of the plant by diffusion, following the concentration gradient (from higher to lower concentration).

Importance:

• Gaseous exchange supports photosynthesis, respiration, and transpiration, all of which are essential for plant growth, energy production, and maintaining water balance.

This delicate process ensures plants contribute to the oxygen levels in the atmosphere while taking in CO₂ needed for their growth.