Excretion, the process by which animals and plants rid themselves of waste products and of the nitrogenous by-products of Metabolism. Through excretion organisms control osmotic pressure—the balance between inorganic ions and water—and maintain acid-base balance. The process thus promotes homeostasis, the constancy of the organism’s internal Environment.
Plants have no special organs for removal of wastes. The waste products of Respiration and Photosynthesis are used as raw materials for each other. Oxygen gas produced as a by-product of photosynthesis is used up during respiration and carbon dioxide produced during respiration is used up during photosynthesis.
Excretion is carried out in the plants in the following ways:
- The gaseous wastes, oxygen, carbon dioxide and water vapour are removed through stomata of leaves and lenticels of stems.
- Some waste products collect in the leaves and bark of trees. When the leaves and bark are shed, the wastes are eliminated.
- Some waste products are rendered harmless and then stored in the plant body as solid bodies. Raphides, tannins, resins, gum, rubber and essential oils are some such wastes.
Excretion in animals
Many unicellular organisms like Amoeba throw out their wastes by diffusion from their body surface. Protozoan’s have no organs for excretion. As they live in an aquatic habitat, their wastes are eliminated by diffusion through the plasma membrane.
Simple multicellular organisms like Hydra throw out solid waste matter through their mouth. Higher multicellular organisms have well-defined specialized excretory organs. These organs could be simple tubular structures as in flatworms and leech.
The excretory organs of insects (e.g., grasshopper, cockroach and housefly) are also tubular. They remove nitrogenous wastes from the body fluid and help in maintaining the water balance in the body. In vertebrates, the main organs of excretion and maintenance of water balance are the kidneys.
Excretory System in Human
Our excretory system consists of kidneys, blood vessels that join them, ureters, urinary bladder and urethra. They help produce and excrete urine.
There are two bean-shaped kidneys that lie in the abdominal cavity, one on either side of the vertebral column. The kidneys are reddish brown. Each of them is about 10 cm long and weighs about 150 g. Although they weigh less, they receive a lot of blood for filtration.
A volume of blood nearly equivalent to that in the whole body passes through the kidneys every four or five minutes. The kidneys produce urine to filter out the waste products, like urea and uric acid, from the blood.
Urine leaves each kidney through a tube called ureters. The ureters from both the kidneys are corrected to the urinary bladder that collects and stores urine. Ureters carry urine from the kidneys into the urinary bladder. The urethra is a canal that carries urine from the bladder and expels it outside the body.
Each kidney is enclosed in a thin, fibrous covering called the capsule. A renal artery brings blood into the kidney, along with nitrogenous waste materials. After filtration in the kidney, the purified blood leaves the kidney through a renal vein.
Structure and Function of a Nephron
A nephron consists of a long coiled tubule and the Malpighian corpuscle. The tubule of the nephron is differentiated into the proximal convoluted tubule, Henle’s loop and the distal convoluted tubule. The distal tubule opens into the collecting duct. At the proximal end of the nephron is the Malpighian corpuscle, which consists of Bowman’s capsule and the glomerulus. Bowman’s capsule is a double-walled cuplike structure which surrounds the dense Network of blood capillaries called the glomerulus.
The process of excretion in nephron
The process of excretion may be divided into three stages- tubular secretion.
Filtration: Filtration of blood occurs under high pressure in the nephrons of the kidney. Blood enters the glomerulus through the afferent arteriole (with a wider lumen) and leaves through the efferent arteriole (with a narrow lumen). Therefore, blood passes through the glomerulus under pressure. This results in filtration of blood.
Selective reabsorption: Some Molecules of the glomerular filtrate are selectively reabsorbed into the blood. The glomerular filtrate flows through the proximal convoluted tubule, the U-shaped Henle’s loop and the distal convoluted tubule. It contains many useful substances such as glucose, amino acids and salts.
Tubular secretion: Some nitrogenous waste products like creatinin and some other substances like potassium ions are removed from the blood by the distal convoluted tubule, and are then added to the urine. This is called tubular secretion.
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Excretion in plants is the process by which plants remove waste products from their cells. The main waste products produced by plants are water, oxygen, and carbon dioxide. Plants also produce other waste products, such as ammonia, uric acid, and urea.
Plants excrete waste products through a variety of mechanisms, including Transpiration, guttation, and leaf abscission. Transpiration is the process by which plants lose water vapor through their leaves. Guttation is the process by which plants lose water droplets through their leaves. Leaf abscission is the process by which plants shed their leaves.
The type of waste product produced by a plant and the mechanism by which it is excreted depends on the plant species and the environmental conditions. For example, plants that grow in dry environments tend to produce more water vapor as a waste product than plants that grow in wet environments.
Excretion is an important process for plants because it helps to maintain the internal balance of the plant. Waste products can build up in the plant’s cells and damage the plant if they are not removed. Excretion also helps to prevent the plant from becoming too acidic or too alkaline.
Types of waste products produced by plants
The main waste products produced by plants are water, oxygen, and carbon dioxide. Plants also produce other waste products, such as ammonia, uric acid, and urea.
- Water is the most abundant waste product produced by plants. Plants lose water through their leaves in a process called transpiration. Transpiration is necessary for plants to take up water and nutrients from the Soil.
- Oxygen is a waste product produced by plants during photosynthesis. Photosynthesis is the process by which plants use sunlight to convert carbon dioxide and water into glucose and oxygen.
- Carbon dioxide is a waste product produced by plants during respiration. Respiration is the process by which plants break down glucose to produce energy.
- Ammonia, uric acid, and urea are waste products produced by plants when they break down proteins. These waste products are usually excreted in the form of urine.
Mechanisms of excretion in plants
Plants excrete waste products through a variety of mechanisms, including transpiration, guttation, and leaf abscission.
- Transpiration is the process by which plants lose water vapor through their leaves. Transpiration is necessary for plants to take up water and nutrients from the soil. Water vapor moves from the plant’s cells to the air through tiny pores in the leaves called stomata.
- Guttation is the process by which plants lose water droplets through their leaves. Guttation occurs when water pressure builds up in the plant’s cells. The water droplets are released through special pores on the leaves called hydathodes.
- Leaf abscission is the process by which plants shed their leaves. Leaf abscission is a natural process that helps plants to conserve water and nutrients. Leaves are shed when they are no longer able to photosynthesize efficiently.
Factors that affect excretion in plants
The type of waste product produced by a plant and the mechanism by which it is excreted depends on the plant species and the environmental conditions. For example, plants that grow in dry environments tend to produce more water vapor as a waste product than plants that grow in wet environments.
The following are some of the factors that affect excretion in plants:
- Plant species. The type of plant species affects the type of waste products produced and the mechanisms by which they are excreted. For example, some plants produce ammonia as a waste product, while others produce uric acid.
- Environmental conditions. The environmental conditions, such as temperature, humidity, and Light intensity, affect the type of waste products produced and the mechanisms by which they are excreted. For example, plants that grow in hot, dry environments tend to produce more water vapor as a waste product than plants that grow in cool, wet environments.
- Plant Health. The health of the plant affects the type of waste products produced and the mechanisms by which they are excreted. For example, diseased plants may produce more waste products than healthy plants.
Importance of excretion for plants
Excretion is an important process for plants because it helps to maintain the internal balance of the plant. Waste products can build up in the plant’s cells and damage the plant if they are not removed. Excretion also helps to prevent the plant from becoming too acidic or too alkaline.
The following are some of the benefits of excretion for plants:
- Maintains internal balance. Excretion helps to maintain the internal balance of the plant by removing waste products from the cells. This helps to prevent the build-up of waste products, which can damage the plant.
- Prevents acidity or alkalinity. Excretion helps to prevent the plant from becoming too acidic or too alkaline. This
Here are some frequently asked questions about excretion in plants:
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What is excretion?
Excretion is the process by which plants remove waste products from their bodies. -
What are the main waste products of plants?
The main waste products of plants are water, carbon dioxide, and oxygen. -
How do plants excrete waste products?
Plants excrete waste products through their leaves, stems, and roots. -
What are the benefits of excretion for plants?
Excretion helps plants to maintain a healthy internal environment and to avoid the build-up of toxic waste products. -
What are the risks of excretion for plants?
Excretion can lead to the loss of water and nutrients from plants. -
How can plants minimize the risks of excretion?
Plants can minimize the risks of excretion by absorbing water and nutrients efficiently and by excreting waste products in a controlled manner. -
What are some examples of plant adaptations that help them to excrete waste products?
Some examples of plant adaptations that help them to excrete waste products include the presence of stomata on leaves, the production of xylem sap, and the formation of root hairs. -
What are some of the challenges that plants face in excreting waste products?
Some of the challenges that plants face in excreting waste products include the need to maintain a healthy internal environment, the need to avoid the build-up of toxic waste products, and the need to minimize the loss of water and nutrients. -
What are some of the ways that scientists are working to improve our understanding of plant excretion?
Some of the ways that scientists are working to improve our understanding of plant excretion include studying the structure and function of plant cells, studying the chemical composition of plant waste products, and studying the role of plant HORMONES in regulating excretion. -
What are some of the potential applications of research on plant excretion?
Some of the potential applications of research on plant excretion include developing new methods for improving plant Growth and productivity, developing new methods for controlling plant pests and diseases, and developing new methods for producing biofuels.
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Which of the following is not a waste product of plants?
(A) Water
(B) Oxygen
(C) Carbon dioxide
(D) Urea -
Plants excrete waste products through their:
(A) Roots
(B) Leaves
(C) Stems
(D) Flowers -
The process of removing waste products from the body is called:
(A) Excretion
(B) Digestion
(C) Respiration
(D) Photosynthesis -
The main waste product of plants is:
(A) Water
(B) Oxygen
(C) Carbon dioxide
(D) Urea -
Plants excrete waste products through a process called:
(A) Transpiration
(B) Guttation
(C) Respiration
(D) Photosynthesis -
Transpiration is the process of:
(A) Plants taking in water and nutrients from the soil
(B) Plants releasing water vapor into the air
(C) Plants converting sunlight into energy
(D) Plants producing oxygen -
Guttation is the process of:
(A) Plants taking in water and nutrients from the soil
(B) Plants releasing water vapor into the air
(C) Plants converting sunlight into energy
(D) Plants producing oxygen -
The main function of leaves is to:
(A) Take in water and nutrients from the soil
(B) Release water vapor into the air
(C) Convert sunlight into energy
(D) Produce oxygen -
The main function of roots is to:
(A) Take in water and nutrients from the soil
(B) Release water vapor into the air
(C) Convert sunlight into energy
(D) Produce oxygen -
The main function of stems is to:
(A) Take in water and nutrients from the soil
(B) Release water vapor into the air
(C) Convert sunlight into energy
(D) Support the plant