The definition of respiration in plants tells us that it is usually a process in which the plants use atmospheric oxygen for oxidising glucose and other respiratory substrates like proteins, fats, etc. The respiratory substrates are usually the organic nutrients that are oxidised at the time of respiration.
These substrates are normally high-energy biomolecules that can produce energy, carbon dioxide, and water, the definition of respiration in plants also states that plants usually undergo cellular respiration in the presence or absence of light. Dark respiration is the respiration that occurs in the absence of light, while photorespiration occurs only in the presence of sunlight.
There are usually 3 types of plant respiratory cycle. The first type of cellular respiration in plants is called glycolysis, it takes place in the cytoplasm and produces energy under anaerobic respiration. The second type is known as Krebs’s cycle, which takes place in the mitochondrial matrix.
The third/last stage is called oxidative phosphorylation, it occurs in the mitochondrial membrane by the electron transport system.
What is the simple definition of respiration?
Do you want to know the simple definition of respiration? Respiration in plants can be simply defined as a cycle/chain of chemical reactions that help the plants to synthesise energy and helps them to sustain themselves.
Plant respiratory cycle
Plants usually respire 24 hours a day just like us humans. This is carried out both day and night to oxidise the glucose into by-products like water, carbon dioxide, energy, etc. Plants usually produce glucose and oxygen during photosynthesis with the help of water and carbon dioxide with the effect of sunlight and chlorophyll.
We should also note that respiration in plants is a process that occurs simultaneously throughout the whole day, while photosynthesis only takes place during the daytime in the presence of sunlight. The rate of respiration at the night increases as there is no pressure on photosynthesis at the night.
Cellular respiration in plants
The cellular respiration in plants usually involves 3 major paths to oxidise glucose into energy (it is also called ATP). In cellular respiration, glucose is firstly oxidised into pyruvate by a chain of enzymes. The pyruvate then undergoes oxidation and is converted into acetyl coenzyme-A by an enzyme pyruvate dehydrogenase.
The acetyl coenzyme-A then enters the Krebs cycle and is then converted into carbon dioxide protons and electrons through the combination of different enzymes.
The protons and electrons which were released from the Krebs cycle then participate in the electron transport system. The oxygen combines the electron and the proton to make a water molecule.
Types of respiration in plants
You need to understand the definition of respiration in plants to understand the types of respiration. The respiration in plants can be categorised into 2 types based on the requirement of oxygen, the two types of respiration in plants are as follows:
Aerobic respiration- It is the type of respiration that occurs in the presence of oxygen in the sky. A plant usually uses oxygen in oxidising glucose into low-energy molecules like water and carbon dioxide. Aerobic respiration releases a very high amount of energy which is further used in driving ATP synthesis. The ATP is broken down into ADP which is an inorganic phosphate that in turn releases energy. Plants use energy for different cellular functions.
Anaerobic respiration- Anaerobic respiration is intramolecular respiration that usually occurs in succulent plants such as cacti, germinating seeds, etc. It occurs in the absence of oxygen and it results in the incomplete oxidation of the respiratory substrates into carbon dioxide and ethyl alcohol by releasing energy. Thus, we can note that anaerobic respiration in plants is related to alcohol fermentation. It occurs in the cytoplasm, and it produces 2 ATP molecules. It also involves incomplete oxidation of a glucose molecule.
Mechanism of respiration
Just like us humans and any other organism, plants also need oxygen for respiration and for producing energy. We know that respiration takes place in different parts like roots, stems, and leaves.
Respiration in roots- Roots usually respire by getting the oxygen mixed air from the soil through the root hairs. Root hairs are tubular structures that are in direct contact with the soil particles. The oxygen is spread to the different parts of the root through the root hairs. The roots release carbon dioxide when they are consuming oxygen. The carbon dioxide which is released by the root is then absorbed by the plants to prepare food and release oxygen.
Respiration in Stems- Stems of herbaceous usually respire through a stomatal pore which is found on the epidermis of the stem. We should note that stems of woody plants respire through lenticels which are found on the periderm of the stem. So, we can conclude that both lenticels and stomatal pore allow the entry of oxygen inside the plants’ intercellular spaces and then they release carbon dioxide into the sky.
Respiration in leaves- Stomata which are usually present in the lower epidermis layer of the leaf allow gaseous exchange between leaves and the environment. The Guard cells usually control the stomatal activities which also controls the gaseous exchange
Conclusion
The definition of respiration in plants tells us that it is usually a process in which the plants use atmospheric oxygen for oxidising glucose and other respiratory substrates like proteins, fats, etc. The respiratory substrates are usually the organic nutrients that are oxidised at the time of respiration. These substrates are normally high-energy biomolecules that can produce energy, carbon dioxide, and water, the definition of respiration in plants also states that plants usually undergo cellular respiration in the presence or absence of light.
Plants usually respire 24 hours a day just like us humans. This is carried out both day and night to oxidise the glucose into products like water, carbon dioxide, energy, etc. The cellular respiration in plants usually involves 3 major paths to oxidise glucose into energy (it is also called ATP). The respiration in plants can be categorised into 2 types based on the requirement of oxygen, which are aerobic and anaerobic respiration. Just like us humans and any other organism, plants also need oxygen for respiration and for producing energy. We know that respiration takes place in different parts like roots, stems, and leaves.