Excretion In Plants And Transpiration: Definition, Types, Transpiration
Excretion and transpiration are the two main physiological activities in plants. Plants lack excretory organs but excrete wastes through stomata, lenticels, and guttation. Transpiration helps in the uptake of nutrients and cooling and provides the driving force for water flow and minerals from roots to shoots. Excretion and transpiration in a plant are equally important for maintaining the balance of internal conditions and distribution of food in a plant body.
This Story also Contains
- What is Excretion in Plants?
- Types of Waste Products in Plants
- Transpiration in Plants
- Role of Transpiration
- Comparison Table – Excretion vs Transpiration
- Importance of Excretion and Transpiration
- Excretion in Plants and Transpiration NEET MCQs (With Answers & Explanations)
- Recommended Video On 'Excretion in Plants and Transpiration'
What is Excretion in Plants?
Excretion in plants is a process through which plants rid themselves of metabolic byproducts to maintain the cellular and general health of the plant. Plants lack specialised excretory organs like animals but have different ways of excreting waste products.
Types of Waste Products in Plants
The waste products excreted by plants are:
Gaseous Wastes
Oxygen: It is an excess by-product of photosynthesis. Thus, it is released in the atmosphere via stomata on leaves.
Carbon Dioxide: It is a product of respiration and also given off through stomata mainly during the night when photosynthesis stops.
Liquid Wastes
Water: Excess water absorbed from the soil is eliminated through transpiration and guttation.
Organic Acids: Examples include malic and citric acids, which combine to adjust pH or detoxify excess nutritional elements.
Solid Wastes
Resins and Latex: These are excreted by the secretions of some plants while defending themselves against certain pests and diseases. They collect in certain specialised cells, that later on get released with the shedding of plant tissues.
Transpiration in Plants
Transpiration is the water movement from the soil into the plant and then evaporating into the atmosphere mainly from the stomata of leaves and stems. It is an important physiological process that regulates internal conditions.
Role of Transpiration
Transpiration plays an important role in:
Cooling Effect on Plants
Transpiration cools plants due to evaporative cooling. Since water is evaporated from the surface of leaves, it takes up heat and hence lowers the temperature of the plant, avoiding overheating. This cooling effect is essential in the proper functioning of enzymes and maintenance of the temperature for plant growth.
Nutrient Transport
Transpiration-stream is the process by which water and other nutrients dissolved in the soil are transported to different parts of the plant. The evaporation of water pulls water and nutrients through xylem vessels. Thus ensuring that all regions of plants receive the necessary minerals and nutrients.
Maintaining Water Balance
It helps maintain the water balance of the plant. The plants control the rate of water loss via stomata. This in turn regulates their internal water supplies and maintains the right level of hydration in the surrounding soil.
Comparison Table – Excretion vs Transpiration
The difference between excretion and transpiration is:
Feature | Excretion | Transpiration |
Definition | Removal of metabolic waste | Loss of water vapor from plant surface |
Structures Involves | No special structures | Stomata, cuticle, lenticels |
Types of Waste | CO₂, water, resins | Water vapor |
Function | Detoxification, homeostasis | Cooling, nutrient transport |
Example | Resins in pine trees | Evaporation from leaves |
Importance of Excretion and Transpiration
Excretion and transpiration are two vital procedures that influence the health of plants and the equilibrium of ecosystems. Excretion helps to get rid of metabolic waste products, resulting in gaseous byproducts, liquid organic acids, and solid substances like resins. This is important to keep cellular homeostasis. Transpiration enables a cooling system in the plants, promotes transport of nutrients and helps in the water balance.
Together these processes control the internal conditions and hence ensure survival at the level of the single plant. It also contributes towards ecological balance through their impacts on water cycling and nutrient distribution. It illustrates the interrelationship of plant physiology and environmental dynamics.
Excretion in Plants and Transpiration NEET MCQs (With Answers & Explanations)
The key concepts to be covered under this topic for different exams are:
Excretion and Transpiration in Plants
Excretion vs Transpiration
Practice Questions for NEET
Q1. The consequence of a high rate of transpiration is
Death of some plants due to excessive loss of water
Plants suffer from loss of turgidity
Lower concentration of water in the cell sap
All of these
Correct answer: 4) All of these
Explanation:
Some plants die as a result of excessive water loss: A plant may get dehydrated and even die if it loses too much water through transpiration, or the evaporation of leaves.
The pressure inside plant cells that keeps them firm is called turgidity, and it is lost in plants. The plant wilts when its cells shrink due to excessive water loss.
Reduced water content in cell sap: When a plant's cells contain less water, the fluids within—known as sap—become more concentrated with other materials, such as salts.
Hence, the correct answer is option 4)All of these.
Q2. Which one of the following will not directly affect transpiration?
Temperature
Light
Wind Speed
Chlorophyll content of leaves
Correct answer: 4) Chlorophyll content of leaves
Explanation:
Transpiration is the process by which plants lose water in the form of dewdrops on the surface of the leaves, this does not involve the chlorophyll content in the leaves and is indifferent to it. Temperature, light, and wind speed are determinants of the process on the other hand.
Hence, the correct answer is option 4) Chlorophyll content of the leaves.
Q3. Transpiration and root pressure cause water to rise in plants by:
Pushing it upward
Pushing and pulling it, respectively
Pulling it upward
Pulling and pushing it, respectively
Correct answer: 4) Pulling and pushing it, respectively
Explanation:
Transpiration creates the environment for the passive absorption of water by creating a pulling force, while root pressure develops because of the active absorption of solutes and it pushes the water up the stem. Transpiration primarily occurs through stomata and is driven by evaporation, which creates a negative pressure that pulls water from the roots through the plant. Root pressure, on the other hand, is generated when roots actively absorb minerals and water from the soil, causing a positive pressure that pushes water upwards. Both processes contribute to the movement of water through the plant, maintaining turgor and facilitating nutrient transport. While transpiration is the dominant force under normal conditions, root pressure can provide additional support, especially in the early morning or at night.
Hence, the correct answer is option 4) pulling and pushing it, respectively.
Also Read:
Recommended Video On 'Excretion in Plants and Transpiration'
Frequently Asked Questions (FAQs)
Transpiration has quite several vital functions, including:
Temperature Control: Evaporative cooling does control the temperature of the plant.
Mineral Nutrient Transport: This promotes the flow of water and nutrients in solution from the roots to the leaves and other parts of plants.
Water Balance: Helps balance water in the organism and hence regulates internal supply toward the prevention of overhydration and dehydration.
- Water Cycle: Plants transfer water vapour into the atmosphere through the process of transpiration, thus participating in the global water cycle and therefore further enhancing the development of cloud formation/precipitation.
Plants get rid of metabolic by-products. A plant will, however, not have an organ specifically for excretion but instead form methods for ridding metabolic waste: gases, liquids, and solids to ensure cellular health and homeostasis.
Plants excrete waste by several mechanisms:
Gaseous wastes include oxygen and carbon dioxide that are exhaled out through the stomata on the leaves.
Liquid wastes consist of an excess of water and organic acids that are excreted out in the process of transpiration and guttation.
Solid wastes, such as resins and latex, are particularly secreted into special cells or tissues; most of these wastes are shed along with parts of plants, like the shedding of leaves and bark.
Transpiration refers to the process wherein plants absorb water from the soil by their roots, transport the same throughout the plant, and finally give off to the atmosphere in the form of water vapour through the stomata present in leaves and stems. This is an important process in the regulation of water, transportation of nutrients, and temperature control within the plant.
Factors that affect the rate of transpiration of plants include:
Temperature: With an increase in temperature, the evaporation as well as the transpiration rate rises.
Humidity: Low humidity provides conditions that raise transpiration by increasing the gradient for the outflow of water vapour.
Wind: The wind removes water vapour from the leaf surface and raises the rate of transpiration.
Light: With a high intensity of light, the stomata open and it raises the rate of transpiration.
Soil Moisture: A proper amount and adequate soil moisture should be available to promote the optimum rate of transpiration; inadequate amounts of water lower the rate of transpiration.