Respiration In Plants: Definition, Types, Importance, Examples

What Is Respiration In Plants?

Respiration in plants is the process where plants, after converting glucose and oxygen into energy, release carbon dioxide and water as a metabolic side. This metabolic process is an essential part of maintaining life in the plants and continues throughout the day and night.

In contrast to the photosynthesis, undertaken in the chloroplasts, respiration in plants happens in cell mitochondria. All this process depots in maintaining the life mechanism in the cell and the development of a whole plant collectively.

It is the biochemical process in which biochemical energy stored in glucose is broken down to form ATP, the cell's energy currency. The process includes glycolysis, the Krebs cycle, and the electron transport chain.

The general formula for aerobic respiration in plants is:

C₆H ₁₂0 ₆ + 6O ₂ → 6CO ₂ + 6H ₂0 + Energy (ATP)

Do Plants Breathe?

• Plants "breathe" in the sense that they are capable of exchanging gases with the environment.

• Gas exchange is required for respiration and photosynthesis.

• Plants take up oxygen and give out carbon dioxide through stomata, lenticels, and root cells.

• In contrast to animals, plants do not possess specialised respiratory organs; in them, gas exchange takes place through various plant tissues.

• Breathing ensures the supply of oxygen for cellular respiration.

• Efficient gas exchange is important for metabolic activities going on in a plant and overall plant health.

Respiration In Stems

• Lenticels on the bark of woody stems provide a surface for the exchange of gases.

• In herbaceous stems, it takes place directly through the epidermal cells.

• Oxygen is absorbed through lenticels and diffuses through to the inner tissues.

• Carbon dioxide, which is the product of cellular respiration, diffuses out through the same openings.

• Stem respiration is essential to produce energy in cells of the stem for its growth and transport of nutrients and water.

Respiration In Roots

• Roots have many small root hairs which increase surface area for gas exchange.

• In waterlogged soils, aerenchyma or air spaces in root tissues allow for oxygen transport.

• O₂ from the soil diffuses into the root hairs and is delivered to all of the root's cells.

• CO₂, a product of respiration, diffuses out into the soil.

• Root respiration provides the energy to take up nutrients and water.

• Facilitates maintenance of the root's metabolic activities and growth.

Respiration In Leaves

• Gas exchange is controlled by the stomata on the leaf surface.

• The thin, flat nature of the leaves allows for efficient gas diffusion.

• During the day, the stomata are open. This allows the take-up of carbon dioxide needed for photosynthesis and oxygen to be released.

• Oxygen is also taken up for respiration, and carbon dioxide, which is a byproduct of respiration, diffuses out.

Respiration In The Leaf

• Supports the energy requirements of photosynthesis.

• It thus becomes essential for the maintenance of cellular processes and the general health of the leaf.

Types Of Respiration In Plants

In essence, plant respiration can be broadly categorised into two fundamental types: aerobic and anaerobic respiration.

Aerobic Respiration

• Involves the presence of oxygen.

• It includes glycolysis, the Krebs cycle, and the electron transport chain.

• It results in the production of carbon dioxide, water, and a significant portion of ATP.

• The amount of ATP obtained is utilized in accomplishing the activities essential for living organisms.

• This is especially beneficial while making and preserving plant tissues.

Anaerobic Respiration

• It can happen in the absence or when there is little oxygen.

• Commonly found in waterlogged soils or during intense metabolic activity.

• Yields far less energy than aerobic respiration.

• Forms waste products like ethanol and lactic acid, which can be toxic if accumulated.

Cellular Respiration In Plants

The details are given below:

Glycolysis

• Location: cytoplasm

• Glucose is broken down into two molecules of pyruvate.

• Yields a net gain of 2 ATP and 2 NADH molecules.

• Is an anaerobic process.

Krebs Cycle (Citric Acid Cycle)

• Location: Mitochondrial matrix

• Pyruvate is first converted into acetyl-CoA, which subsequently enters the cycle.

• Yields CO2, NADH, FADH2 and 2 ATP per glucose molecule.

• Completes oxidation of glucose derivatives.

Electron Transport Chain (ETC)

• Location: Inner mitochondrial membrane

• NADH and FADH2 donate electrons to the chain.

• Electrons pass through protein complexes, driving proton pumping.

• Protons flow back through ATP synthase, generating 34 ATP molecules.

Factors Affecting Respiration In Plants

Several factors can influence the process of respiration in green plants:

Temperature

• An increase in temperature normally increases respiration rates to a certain optimum value.

• Very high temperatures can cause the denaturation of enzymes involved in respiration.

Oxygen Concentration

• Sufficient oxygen: Oxygen should be optimally present for aerobic respiration.

• Low oxygen conditions promote anaerobiosis.

Sufficient water

• Water should be optimally present to carry out enzymatic activities and other cellular activities.

• Drought stress reduces the ability of the plant cells to respire.

Light

• It indirectly affects respiration, as light is essential for photosynthesis and consequently determines the level of carbohydrate availability.

• Plants respire at all times, but they will only photosynthesise in the light.

Nutrients

• Metabolic nutrients, particularly Nitrogen, Potassium, and Phosphorus.

• Scarcity of any required nutrient will limit both respiration and.

Comparison Between Photosynthesis And Respiration

Plant Adaptations To Achieve Efficient Respiration

Plants develop several adaptations to carry out respiration efficiently in different conditions:

Root Respiration

• Aerenchyma tissues in roots that allow the exchange of gases in waterlogged soils.

• The large surface area of roots readily absorbs oxygen.

Leaf Respiration

• Stomata control the gas exchange; open during the day and close at night.

• Laterally flattened leaves increase the time for gas exchange.

Aquatic Plants

• Leaves float on the water surface while air-filled cavities above ground ensure oxygen supply.

Desert Plants

• Reduced stomata openings with thick cuticles to reduce loss of water and promote respiration.

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