gaseous exchange in plants

Gaseous exchange in plants

In plants, gaseous exchange primarily occurs through the stomata on the leaves, lenticels on the stems, and sometimes through specialized roots in certain plants like mangroves and ficus.

Gaseous exchange in the leaves

1. Stomata and Guard Cells: The stomata are tiny pores on the surface of leaves that facilitate the exchange of gases like oxygen and carbon dioxide. These pores are surrounded by guard cells, which regulate their opening and closing.
2. During the Day: In the presence of sunlight, guard cells absorb water through osmosis, becoming turgid. This causes the stomata to open, allowing atmospheric air to enter the leaf. Inside the leaf, oxygen (produced during photosynthesis) accumulates in the air spaces, while carbon dioxide (used during photosynthesis) is lower in concentration.
3. Diffusion of Gases: Carbon dioxide from the atmosphere diffuses into the plant cells for photosynthesis, while oxygen diffuses out into the atmosphere. This is because gases move from regions of higher concentration to lower concentration.
4. During the Night: At night, in the absence of light, photosynthesis stops and the guard cells do not absorb water, causing the stomata to close partially. However, respiration continues, and oxygen in the air spaces moves into the plant cells, while carbon dioxide produced during respiration moves out into the atmosphere through the partially open stomata. Therefore, during the night, plants release carbon dioxide instead of oxygen.

Gaseous exchange through lenticels

Lenticels: These are small pores found in the bark of woody stems and roots, made up of loosely packed cork cells. They enable gaseous exchange between the plant's internal tissues and the external environment. Lenticels allow oxygen to enter the plant for cellular respiration and carbon dioxide to exit.

Gaseous exchange in the lenticels

Gaseous exchange through the roots (breathing roots)

1. Breathing Roots: Some plants, such as mangroves, have specialized roots known as breathing roots that allow for gaseous exchange. These roots have a thin epidermis that facilitates the diffusion of gases.
2. Oxygen Diffusion: Oxygen from the atmosphere diffuses into the root cells through the epidermis because the concentration of oxygen in the atmosphere is higher than in the root cells.
3. Respiration and Carbon Dioxide Diffusion: The root cells use oxygen for respiration, producing energy and releasing carbon dioxide as a byproduct. The concentration of carbon dioxide in the root cells becomes higher than in the atmosphere, causing carbon dioxide to diffuse out of the root cells into the surrounding air through the epidermis.

Breathing roots

Importance of gaseous exchange in plants

1. Carbon Dioxide for Photosynthesis: Gaseous exchange allows plants to obtain carbon dioxide, which is one of the essential raw materials for photosynthesis.
2. Oxygen for Respiration: Oxygen is also obtained through gaseous exchange, which is necessary for respiration, a process that produces energy for the plant's growth and maintenance.
3. Elimination of Excess Carbon Dioxide: At night, when photosynthesis stops and respiration continues, excess carbon dioxide is released through gaseous exchange. If carbon dioxide were to accumulate, it would be harmful to the plant, so this process ensures the plant maintains a healthy balance of gases.