Gaseous Exchanges in Plants

Chapter 10 Gaseous Exchanges – 10th Class Biology Notes

Question 1: Define gaseous exchanges, breathing and cellular respiration?

Answer: Gaseous exchanges: Taking in oxygen and giving out of carbon dioxide is termed as gaseous exchange.  “OR” The exchange of gases in body of living organisms through a characteristic way is called gaseous exchanges.

Gaseous exchanges is the diffusion of gases from a region of its higher concentration to a region of lower concentration in the living organisms. The term is used both for O2 and CO2 inhalation and exhalation.

Animals can only respire. During respiration inhalation of O2 and exhalation of CO2 takes place. While in plants gaseous exchanges takes place through respiration and photosynthesis. During photosynthesis plants take in Co2 and release O2.


Breathing: The term breathing is used for the process through which animals take air in their bodies to get oxygen from it and then give out the air for getting rid of carbon dioxide.


Cellular respiration: Cellular respiration is the process in which the C-H bonds in food are broken by oxidation reduction reactions and the energy is transformed into ATP.


Types of respiration: Respiration has following two types.


  • Aerobic respiration: In aerobic respiration, oxygen is used and there is complete oxidation of the food material. Carbon dioxide and water are also produced in this process.
  • Anaerobic respiration: The type of respiration that occurs in the absence of oxygen is called anaerobic respiration. In this type of respiration incomplete oxidation of glucose takes place and very less amount of energy is produced.

Question 2: How do the different parts of the plant body exchange gases with the environment?


Answer: Gaseous exchange in plants: Plants have no specialized organs for gaseous exchanges like animals, such as lungs or gills. Plants have large surface area and gaseous exchanges occur through them by diffusion through small pores called stomata.

Stomata are present on epidermis of leaves. Plant roots obtained dissolved oxygen through root hairs. Land plants get oxygen from air by their open stomata during day time. In woody parts of gaseous exchanges takes place through lenticels (small pores present on woody parts of plants).

After entering cell through these pores gases inters into respiratory surface (center) called mitochondrion. In mitochondria complete oxidation of food takes place and release energy, carbon dioxide, and water. CO2 are diffused to outside and are then used in process of photosynthesis. Aquatic plants take CO2 for photosynthesis and Oxygen for respiration from dissolved gases in water by diffusion of gases.



Organisms need energy in the form of ATP for their activities


In young stems and leaves, some gaseous exchange also occurs through the cuticle which is present over their epidermis.

Question 3: What is the purpose of gaseous exchanges in plants? Also write a short note on stomata?

Answer: Purpose of gaseous exchanges in plants: Plants need energy to perform all their activities. This energy is only produced by respiration process. As respiration occurs only in the presence of oxygen and oxygen inters the plants through gaseous exchanges. So gaseous exchanges are necessary in plants.

Stomata (singular: stoma): stomata are small pores on aerial parts of plant body that are used for gaseous exchanges. The pores are bordered by specialized parenchyma cells known as guard cells. Guard cells regulate the opening and closing of stomata.

Both pore (stomata) and guard cells are collectively called stomatal complex. Air containing carbon dioxide and oxygen inters the plant through these pores, which is used in process of respiration and photosynthesis.

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