Types of Respiration in Plants and Their Processes

What is Respiration in Plants

Just like animals, plants respire and require energy as well. They get their portion of energy by the process of respiration wherein the glucose molecules present in the food gets broken down to form carbon dioxide in the presence of water and releases oxygen as a by-product.

Plants make use of this energy to carry out the different life processes and hence, they respire too, just like any other living organism, for their survival. However, if we talk about how do plants respire, their respiration process is much different than that of animals. Unlike animals, every part of the plants can take in oxygen from the surrounding air independently, use it to get energy, and in the end give out carbon dioxide. Let us first define respiration in plants and see how plants respire from different parts.

Respiration Process in Plants

During the process of respiration, in different parts of a plant, a comparatively lower amount of gaseous exchange takes place. Therefore, every part of the plant fulfils and nourishes its own energy requirements.

The leaves, roots and stem of plants tend to exchange gases separately. Leaves consist of tiny pores called stomata which aid in the gaseous exchange. The oxygen which is consumed through stomata gets used up by the cells present in the leaves. This, in turn, helps for disintegrating glucose into carbon dioxide and water.

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Respiration in Leaves

Plant leaves consist of tiny pores which we call stomata. During the process of respiration, the exchange of gases in leaves takes place via stomata. This process is explained below.

Oxygen from the surroundings enters the leaf via stomata and reaches the cells through the process of diffusion. The oxygen that enters the cells of the leaf gets used up in the process of respiration. And the carbon dioxide which gets produced during this process gets diffused out of the leaves through stomata into the air.

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Photosynthesis is the reaction in leaves which makes glucose and the process of respiration breaks it down further. In the photosynthesis reaction, light energy is the energy that goes into the reaction, whereas in respiration, chemical energy is the one that comes out. 

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Respiration in Roots

Plant roots are underground but the cells of the roots need oxygen as well for carrying out the process of respiration and releasing energy.

Plant roots take in air from the spaces between the particles of soil. The air present in these soil particles is in contact with the root hair. Oxygen from this air present in the soil particles tends to diffuse into the root hair and reaches the root cells. Here it is used for the respiration process. The carbon dioxide that is produced in the root cells during the process of respiration gets released out via the same root hair through the process of diffusion.

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If a plant in a pot is over-watered for a longer period of time, it would ultimately die because a lot of water expels the air that is present in between the soil particles. Because of this, oxygen does not reach the roots for carrying our aerobic respiration. Hence, the plant roots tend to respire anaerobically and produces alcohol, which might kill the plant. This is the reason the germinating seeds respire through anaerobic respiration since they are coated with a seed coat that prevents oxygen from entering through it.

Respiration in Stems

In the plant stems, the air gets diffused into the stomata and tends to move through various parts of the cells to carry out the process of respiration. At this stage, the carbon dioxide that gets released also gets diffused through the stomata. Lenticels carry out this gaseous exchange in the woody or higher plants.

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Types of Respiration of Plants

If we talk about plant respiration, there are two different respiratory system in plants depending on the presence or absence of oxygen.

1. Aerobic respiration in plants

2. Anaerobic respiration in plants

Aerobic Respiration

Aerobic respiration is the respiration that occurs when oxygen is present. In anaerobic respiration in plants, oxygen gets utilized to break the chemical bonds in glucose for liberating energy in higher volumes. Most of the animals respire aerobically and the process of aerobic respiration occurs in the mitochondria of the cell. 

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP (energy)

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Anaerobic Respiration

Anaerobic respiration is a respiration which takes place in the absence of oxygen. In the anaerobic respiration, lesser energy gets produced because of incomplete oxidation of food that occurs in the absence of oxygen. During the process of anaerobic respiration, ethyl alcohol and carbon dioxide get produced. This process is also referred to as intramolecular respiration. It occurs in organisms such as yeast, parasitic worms and certain bacteria. 

C₆H₁₂O₆ → CO₂ + alcohol + ATP (energy)