Respiration & Types of Respiration | Botany Optional for UPSC PDF Download

Introduction

Plants, often seen as silent and static, have their own way of "breathing." Respiration in plants is a vital process that enables them to generate energy and sustain their survival. While this process might not be as apparent as it is in humans and animals, it is fundamental to the life of plants. In this article, we will delve into the intricacies of respiration in plants, exploring how it occurs in different parts of these remarkable organisms.

Plants: Living Beings with Breath

Contrary to the perception of plants as inert beings, they actively respire. Just like animals, plants require energy to perform various life processes. Plants obtain this energy through respiration, a process in which glucose, their primary food source, breaks down in the presence of oxygen. This breakdown results in the formation of carbon dioxide and water, accompanied by the release of energy. This energy is indispensable for the plant's day-to-day activities. Therefore, it is safe to say that plants, like other organisms, respire for their survival.

Divergence from Animal Respiration

Plant respiration differs significantly from that of animals. In plants, each part has the ability to independently take in oxygen from the air, utilize it to obtain energy, and release carbon dioxide. This unique ability allows various parts of the plant to function without being constrained by a central respiratory system, as is the case in animals.

Let's explore how respiration occurs in different parts of a plant, particularly in leaves and roots.

Respiration in Leaves

The leaves of plants possess tiny pores on their surface, known as stomata. These stomata play a crucial role in the exchange of gases during respiration. The process unfolds as follows:

• Oxygen from the air enters a leaf through the stomata and diffuses to reach all the cells within the leaf.
• This oxygen is consumed in the cellular respiration processes within the leaf.
• Carbon dioxide, a byproduct of respiration, diffuses out from the leaf into the surrounding air through the same stomata.

It's important to note the stark contrast between photosynthesis and respiration in leaves. While photosynthesis harnesses light energy to produce glucose, respiration yields chemical energy, which is essential for the plant's vitality.

Respiration in Roots

The roots of plants, often hidden beneath the soil, also engage in respiration to generate energy. The intriguing question is: How does respiration occur in roots?

• Plant roots absorb air from the interstitial spaces between soil particles.
• Root hairs, specialized structures in close contact with the soil air, facilitate the diffusion of oxygen from the soil into the root cells.
• Within the root cells, oxygen is employed in respiration.
• Carbon dioxide, produced during respiration, exits the root cells and is expelled into the soil air through the same root hairs, again via the process of diffusion.

However, plants are not impervious to adverse conditions. Overwatering a potted plant for an extended period can have dire consequences. Excess water displaces the air from between the soil particles, depriving the roots of oxygen required for aerobic respiration. Under such conditions, roots may resort to anaerobic respiration, leading to the production of alcohol, which can ultimately prove fatal for the plant.

Similarly, germinating seeds, in their early stages, respire anaerobically due to the impermeable seed coat that restricts the entry of oxygen.

A Note on Time and Place: Respiration in Plants

Plant respiration is a continuous process that occurs both day and night, resulting in the production of carbon dioxide. However, during the daytime, the amount of carbon dioxide released is negligible compared to the substantial oxygen produced through photosynthesis. This underscores the importance of not sleeping under a tree at night, as the nighttime respiration may deplete the oxygen levels in the immediate vicinity.

In summary, respiration in plants is a vital, albeit often overlooked, process that fuels their existence. Understanding how plants respire in different parts, such as leaves and roots, sheds light on the remarkable adaptability of these living beings.

Fermentation: Anaerobic Respiration in Plants

Fermentation, also known as anaerobic respiration, is a remarkable metabolic process that allows certain organisms to respire in the absence of oxygen. This article explores the intricacies of fermentation, its various types, industrial applications, and a comparison with aerobic respiration.

Anaerobic Respiration: Unveiling the Basics

Anaerobic respiration, often referred to as fermentation, is a biological phenomenon where organisms derive energy without the presence of oxygen. In this process, cells metabolize organic compounds to generate energy, albeit with some limitations in efficiency compared to aerobic respiration.

The Three Faces of Fermentation

There are three primary types of fermentation:

• Alcoholic Fermentation: Alcoholic fermentation is a fascinating metabolic pathway that takes place in various organisms, including some plant roots residing in waterlogged soils and certain yeast species, notably Saccharomyces. This type of fermentation involves the conversion of pyruvic acid into ethyl alcohol and carbon dioxide (CO₂). It occurs in two distinct steps.
  Industrial Uses of Alcoholic Fermentation: Alcoholic fermentation finds application in several industries:
  
• Lactic Acid Fermentation: Lactic acid fermentation is observed in certain bacteria (Bacillus), fungi, and vertebrate muscle tissues. It involves the conversion of pyruvic acid into lactic acid.
• Mixed Acid Fermentation: Mixed acid fermentation is a characteristic feature of Enterobacteriaceae, leading to the formation of lactic acid, ethanol, formic acid, and gases like CO₂ and H₂.

Characteristics of Anaerobic Respiration

Comparatively, anaerobic respiration has some distinctive characteristics:

• Efficiency: Anaerobic respiration is less efficient than aerobic respiration, resulting in a lower yield of ATP (adenosine triphosphate), which serves as the energy currency of cells.
• ATP Production: A limited number of ATP molecules are generated per glucose molecule during anaerobic respiration.
• CO₂ Production: It is characterized by the production of carbon dioxide (CO2), which is essential for carbon fixation in photosynthesis.

A Glimpse of Glycolysis and Fermentation

As a part of anaerobic respiration, glycolysis is a critical biochemical process. Glycolysis breaks down glucose into simpler compounds and serves as a precursor to fermentation.

Demonstrating Alcoholic Fermentation

A simple experiment can illustrate the process of alcoholic fermentation:

• Take a Kuhne’s fermentation tube, consisting of an upright glass tube with a side bulb.
• Pour a 10% sugar solution mixed with baker's yeast into the fermentation tube.
• Plug the mouth of the tube with a lid.
• Over time, the glucose solution will ferment, emitting an alcoholic odor, and the solution level in the glass column will decrease due to the accumulation of CO₂ gas.
• The presence of the enzyme zymase in yeast catalyzes the conversion of glucose into alcohol and CO₂.
• Introduce a pellet of KOH into the tube to absorb CO₂, causing the solution level to rise in the upright tube.

An Engaging Activity

You can conduct a hands-on activity to witness the effects of yeast fermentation:

• Take a bottle filled with warm water mixed with baker's yeast and sugar.
• After some time, observe bubbles in the water as yeast produces carbon dioxide.
• Attach a balloon to the bottle's mouth.
• After approximately 30 minutes, the balloon will stand upright due to the accumulation of CO₂.

In conclusion, fermentation, or anaerobic respiration, is a vital process that allows organisms to adapt to oxygen-deprived environments. Understanding the nuances of this metabolic pathway opens doors to various industrial applications and sheds light on the remarkable adaptability of living organisms.