RBSE Class 12 Biology Chapter 7 – Transpiration provides complete information related to Transpiration, types of Transpiration, factors affecting the rate of Transpiration, opening and closing of stomata, guttation, bleeding, different mechanisms of opening and closing of stomata and a lot more related to transpiration in plants. These important questions help students to enhance their conceptual knowledge and are completely prepared from the exam point of view, helping students revise the entire chapter.
The Rajasthan Board Class 12 Solutions help students by providing a strategy to prepare for various board examinations and also for medical exams like NEET, AIIMS, etc. By practising these important questions, students can gain deep knowledge about the topic.
RBSE Class 12 Biology Chapter 7 Important Questions
RBSE Biology Chapter 7: MCQ Type Questions
Q.1. Which of the following is not a part of transpiration?
(a)Leaf.
(b)Stem.
(c)Root.
(d)Raw fruits.
Sol: (c)Root.
Q.2.The maximum amount of transpiration occurs in
(a)Stomata.
(b)Lenticels.
(c)Hydathodes.
(d)All of the above.
Sol: (a)Stomata.
Q.3. How many types of transpiration are there?
(a) One.
(b) Two.
(c) Three
(d) Four.
Sol: (c) Three.
Q.4. Which of the following statements are true?
(a)Hydathodes are present in the bark.
(b)Hydathodes are present on the leaf margin.
(c)Hydathodes are present on the lower surface of the leaf.
(d)Hydathodes are present on the upper surface of the leaf.
Sol: (b)Hydathodes are present on the leaf margin.
Q.5. Which of the following fluids is liberated during the activity of the guttation?
(a)Pure water.
(b)Wastes from plants.
(c)Water and carbon dioxide.
(d)Organic and inorganic substances.
Sol: (a)Pure water
Q.6. The action of stomatal transpiration occurs in ___________.
(a) Stomata.
(b) Leaf vein.
(c) Leaf-blade.
(d) Leaf Base.
Sol: Stomata.
Q.7.How many types of stomata are there?
(a) One.
(b) Two.
(c) Three
(d) Four.
Sol: (d) Four.
Q.8. ___________ consists of a pair of guard cells.
(a) Leaf vein.
(b) Stomata.
(c) Leaf-blade.
(d) Leaf Base.
Sol:(b) Stomata.
Q.9. Which of the following statements are true?
(a) Stomata remain open both during the day and night.
(b) Stomata remain closed both during the day and night.
(c) Stomata remain open during the day and closed at night.
(d) Stomata remain open only during the process of transpiration.
Sol: (c) Stomata remain open during the day and closed at night.
Q.10. ___________ is the biological process of removal of excess water from the aerial parts of the plants.
(a)Transpiration.
(b)Guttation.
(c)Bleeding.
(d)Respiration.
Sol: (a)Transpiration.
Q.11. Which is the most important factor in the regulation of transpiration?
(a)Humidity.
(b)soil water content.
(c)atmospheric pressure.
(d)carbon dioxide concentration.
Sol: (a)Humidity.
Q.12. How many stomata are present per square mm of the leaf surface?
(a) 100-200.
(b) 200-300.
(c) 100-300.
(d) 500-1000.
Sol:(c) 100- 300.
Q.13. Which of the following biological processes is an uncontrolled phenomenon?
(a)Transpiration.
(b)Guttation.
(c)Bleeding.
(d)Respiration.
Sol: (b)Guttation.
Q.14. Who proposed the theory of Active Potassium Ion Transport?
(a) Lloyd.
(b) VonMohl.
(c) Yin & Tung.
(d) Levitt.
Sol: (d) Levitt.
Q.15. The tiny pores present on the surface of the leaves are collectively called stomata.
(a) Leaf Base.
(b) Leaf vein.
(c) Leaf-blade.
(d) Stomata.
Sol: (d) Stomata.
Q.16. Which of the following statements are true?
(a) The rate of transpiration is influenced by the number of leaves.
(b) The rate of transpiration is influenced by the height of the plant
(c) The rate of transpiration is influenced by the structure of the leaves.
(d) The rate of transpiration is influenced by the chlorophyll pigment in the cell.
Sol: (c) The rate of transpiration is influenced by the structure of the leaves.
Q.17. The ascent of sap in plants is due to ___________.
(a) Transpiration
(b) Guttation
(c) Transpiration pull.
(d) Respiration
Sol: (c) Transpiration pull.
Q.18. Loss of water in the form of liquid from the leaf margins is called ___________.
(a) Transpiration.
(b) Guttation.
(c) Bleeding.
(d) Respiration.
Sol: (b) Guttation.
Q.19. Which one of the following will not affect transpiration?
(a) Area of a leaf.
(b) Temperature.
(c) Chlorophyll.
(d) Structure of a leaf.
Sol: (c) Chlorophyll.
Q.20. Which of the following theories was given by Steward?
(a) Starch-Sugar hypothesis.
(b) Guard Cell Photosynthesis.
(c) Starch sugar interconversion.
(d) Malate or potassium ion pump hypothesis.
Sol: (a) Starch-Sugar hypothesis.
RBSE Biology Chapter 7: Short Answer Type Questions
Q.1.What is transpiration? What are the different types of transpiration in plants?
Sol. Transpiration is the biological process of removal of excess water from the aerial parts of the plants. There are three different types of transpiration in plants:
- Stomatal transpiration.
- Lenticular transpiration.
- Cuticular transpiration.
Q.2. What is guttation?
Sol. Guttation is defined as the process of secreting small droplets of water from the hydathodes- modified pores on the margins and on the tip of the leaf. This process causes permanent loss of water from the plants and occurs in low-temperature conditions.
Q.3. What are hydathodes?
Sol. Hydathodes are special structures or a type of pores that discharge water from the interior of the leaf to the surface. They are commonly found in angiosperms.
Q.4. What are the Guard Cells?
Sol. Two bean-shaped cells surrounding a stoma are called Guard Cells. They are also known as the epidermal cells and play a crucial role during the process of transpiration.
Q.5. How does light affect the rate of transpiration in plants?
Sol. The presence of light affects the opening of the stomata, which causes a rise in temperature, resulting in an increase in the rate of transpiration. Absence of light results in the closing of the stomata, which causes a fall in temperature, resulting in a decrease in the rate of transpiration.
Q.6. Write the importance of guttation for plants?
Sol. Guttation plays an important role in all plants with vascular systems. It helps in balancing the amount of water and nutrients and also by the deposition of salt at the margin of pores, it destroys the invading bacteria and other diseases causing organisms .
Q.7. What are the mechanisms of opening and closing of stomata?
Sol. There are different mechanisms in the opening and closing of stomata :
- Steward’s Hypothesis.
- Potassium Ion Theory.
- Starch and sugar Hypothesis.
Q.8. List out the different types of leaves based on the presence of stomata.
Sol. On the basis of the presence of stomata, the leaves are classified into three types:
- Hypostomatic: Stomata are present on the lower surface of the leaves. These types of leaves are found in apple and orange plants.
- Amphistomatic: Stomata are present on both the surface of the leaves. These types of leaves are found in maize,oats, and in some grasses.
- Epistomatic:Stomata are present on the upper surface of the leaves. These types of leaves are found in all floating plants like water lilies, etc.
Q.9. List out the factors affecting stomatal movement in plants?
Sol. Opening and closing of the stomata are called the stomatal movements in plants. Factors affecting stomatal movement in plants are:
- Light – Stomata are open during the day time and closed in the night.
- Temperature- Stomatal opening declines, when the temperature is higher than 30°C.
- Carbon Dioxide (CO2) concentration in the internal leaf – Stomatal opening declines, when the concentration of CO2 is higher than the usual in the internal leaf.
- Water availability – Stomata are open, when the availability of water in plants are very little and vice versa.
- Rate of transpiration-The rate of transpiration increases when stomata are open and the transpiration rates decrease, when the stomata are closed.
Q.10. What are the functions of stomata?
Sol. The main functions of stomata are:
- Helps in preventing water from escaping through open pores.
- Helps in the exchange of gases by opening and closing the pores in the leaves.
- Helps to expel the excess water out from the leaves in the form of water vapour.
- Helps in maintaining the moisture balance in plants by the mechanism of the closing and opening of the stomata.
Q.11. What is Bleeding?
Sol. Oozing of a sap from the cut or damage to internal parts of the plant is called bleeding. In plants, bleeding is mainly caused due to the cut or damage to the xylem vessels. This type of bleeding or leakage is mainly found in the rubber tree and fluid is called the latex from which the rubber is produced.
Q.12. What controls the opening and closing of stomata?
Sol. Guard cells, also called the epidermal cells. They are bean-shaped cells surrounding a stoma that control the opening and closing of stomata.
Q.13. What is the importance of transpiration for plants?
Sol. In all vascular plants, transpiration plays an important role in:
- Keeps the plant and plant cell cool.
- Helps in accessing nutrients from the soil.
- Helps in exchange of gas between the atmosphere and the leaf.
- Carbon dioxide entry: When a plant is transpiring, its stomata are open.
Q.14. What are the drawbacks of transpiration?
Sol. Transpiration results in water scarcity that can damage the plants due to desiccation. A lot of energy is released during transpiration. It also causes wilting of the leaves and results in stunted growth of the plants. During the process of transpiration, plenty of unnecessary water is absorbed by the plants.
Q.15. What is Lenticular transpiration?
Sol. Lenticular transpiration is a type of transpiration, which occurs in the lenticels present on the aerial parts of the plant. Lenticels are the large-sized aerating pores present on the woody surfaces of stems. This type of transpiration occurs under favourable environmental conditions and is only one percent of the total transpiration.
Q.16. Which factors are responsible for the guttation in plants?
Sol. Root pressure, soil moisture level and the rate of transpiration are the main factors responsible for the guttation in plants.
Q.17. Which factors are responsible for the bleeding in plants?
Sol. Pressure of fluids is the main factor responsible for the bleeding in plants. This pressure is also called the turgor pressure. Bleeding in plants is caused by the osmotic flow of water through a selectively permeable membrane.
Q.18. Explain the structure of the stomata?
Sol. Stomata are the tiny, kidney, or bean-shaped pores or openings present in the epidermis of the cell and are surrounded by specialized guard cells. Stomata consists of the cell wall surrounding the stoma.The shape of guard cells usually differs in both monocots and dicots.
Q.19. What are the internal factors affecting the rate of transpiration?
Sol.The internal factors or cellular factors affecting the rate of transpiration are
- Root shoot ratio.
- The orientation of the leaf.
- The water status of the plant.
- Structural Peculiarities of the leaf.
- Total number and distribution of stomata in a leaf.
Q.20. Why do plants need stomata?
Sol. Stomata are the specialized pores or openings present in the epidermis of plant cells, which play a crucial role in gaseous exchange during the process of photosynthesis.
RBSE Biology Class 12: Long Answer Type Questions
Q.1. What is transpiration? Discuss the different types of transpiration in plants.
Sol. Transpiration is the biological process of removal of excess water from the aerial parts of the plants.
The are three different types of transpiration in plants are:
Stomatal transpiration.
This type of transpiration occurs in the stomata of the plants. Stomata are minute pores or openings found in the epidermis of leaves and other parts of the plants except for the root system.
Lenticular transpiration.
This type of transpiration occurs in the lenticels, large-sized aerating pores present on the woody surfaces of stems. Lenticular transpiration occurs continuously during the day and night.
Cuticular transpiration.
This type of transpiration occurs in the cuticle, present on the outer epidermal cells of aerial parts of the plants. Cuticular transpiration occurs continuously during the day and night.
Q.2. Draw a flowchart showing the mechanism of the closing stomata in plants according to the potassium ion theory.
Sol. A flowchart showing the mechanism of the closing of stomata in plants according to the potassium ion theory.
During the Night Time:
Sol.
The opening and closing of the stomata are called the stomatal movements in plants. This is controlled by the concentration of solutes in the guard cell.
There are different mechanisms in the opening and closing of stomata :
The opening and closing depend upon the turgor pressure in the guard cells.
Due to the absorption of water, the guard cells swell, which results in the opening of stomatal pores. Whereas the shrinkage of guard cells, caused due to the loss of water, closes the stomatal pores.
The opening and closing of stomata occur due to turgor changes in guard cells.
When guard cells are turgid, the stomatal pore is open while in flaccid conditions, the stomatal aperture closes.
The opening and closing of stomata are controlled by the concentration of solutes in the guard cell.
They take carbon dioxide required during photosynthesis during the day and they release excess water released in the process of respiration during the night, along with carbon dioxide.
Q.4. Draw a flowchart showing the mechanism of the stomatal opening in plants according to the potassium ion theory.
Sol. The active potassium ion theory was first enumerated by a Japanese scientist named Emamura and Fujino in the 1960s. Later in the year 1974 Levit, modified the theory, which is most valid today.
Here is a flowchart showing the mechanism of the stomatal movement in plants according to the potassium ion theory.
During the day light:
Sol. Transpiration is affected by both internal and external factors. Listed below are environmental or external factors affecting the rate of transpiration.
Light.
Presence of direct light affects the opening of the stomata, which causes a rise in temperature, resulting in an increase in the rate of transpiration. Absence of light results in the closing of the stomata, which causes a fall in temperature, resulting in a decrease in the rate of transpiration.
Available soil water
When the available soil water decreases, the overall rate of transpiration also decreases to a certain limit.
Humidity
Increase in the atmospheric humidity reduces the rate of transpiration, whereas the decrease in the atmospheric humidity increases the rate of transpiration.
Temperature
Increase in the temperature reduces the relative humidity of the atmosphere. This results in an increase in the rate of transpiration
Atmospheric pressure.
The decrease in atmospheric pressure causes an increase in the rate of transpiration.
Wind.
Increase in wind velocity quickly replaces the humid air from the surrounding of the leaves by dry air. Thus, the rate of transpiration increases during the fast blowing winds.
Q.6. Brief out any two mechanisms of opening and closing of stomata.
Sol. The opening and closing of the stomata are called the stomatal movements in plants. This type of movement is controlled by the guard cells, a specialized plant cell present in the epidermis of leaves, stems and other aerial parts of the plants.
There are several hypotheses, which have been proposed to explain the mechanism of opening and closing of stomata.
Starch and sugar hypothesis
This hypothesis was proposed by J.D.Sayre in 1923. This was first explained by Sayre and Lloyd in 1908. This hypothesis was first examined in the guard cells. According to the Starch and sugar hypothesis:
During the day time, the carbon dioxide (CO2) decreases in the guard cell with increasing the pH. As a result, phosphorylase enzymes get activated in the cell with high pH and starch converts to glucose-1 phosphate, which increases the DPD of the guard cell, becomes turgid and opens the stomata.
During the night time, the increase in carbon dioxide (CO2) in the guard cell turns the pH. By which the glucose-1 phosphate converts into starch again and closes the stomata.
Steward’s hypothesis
According to this hypothesis, an increase in pH of guard cells results in the conversion of starch into glucose-1-phosphate and then into glucose-6-phosphate, which finally converts into glucose. As glucose and glucose-6-phosphate are soluble in water when compared to glucose-1-phosphate, results in an increase in the osmotic concentration of the guard cells leading to the opening of the stomata during the day time.
Q.7. Explain the mechanism of guttation with a neatly labelled diagram.
Sol. The process of secreting the water molecules in the form of small droplets from the margins of leaves is called a Guttation. The process of guttation is clearly visible on the leaves of various plants including some grasses.
Guttation is a natural phenomenon, which is observed in the early morning hours, in the form of droplets of liquid on the margins of the leaves of higher plants and on the grasses.
The process of guttation is carried out by the small pores located at the end of the leaf vein called hydathodes. The water releases during the process of guttation are not pure water. They are the solutions of both inorganic and organic salts.
De Barry was the first person to observe the process of guttation in plants in 1869.
Q.8. Explain in brief about stomata with a neatly labelled diagram.
Sol. Stomata are the minute openings, generally found in the epidermis of leaves, stems and other parts of plants. In all green plants, stomata are found in the epidermis of leaves, stems and other organs. There are different types of stomata and are classified based on various criteria, including their structure, functions and their distribution on the surface of the leaves.
Structure of a Stomata
Q.9. What is the significance of Transpiration in Plants?
Sol. The significance of transpiration in plants are:
- Helps in cell division.
- Helps in the proper growth of the plants.
- Helps in maintaining the turgidity of the cells.
- Helps in maintaining water balance within the plant.
- Helps in maintaining osmosis and keeps the cells rigid.
- Helps in the conduction of water and minerals to different parts of the plants.
- Keeps the leaves moist by accumulating hydrophilic salts on the surface of the leaves.
- With the help of suction force, this process helps in the upward movement of water in the plants.
Q.10. Write the difference between Guttation and Transpiration.
Sol. Difference between Guttation and Transpiration.
| Guttation | Transpiration |
| Occurs only during the night. | Occurs only during the day. |
| Secretion of water droplets. | Evaporation of water droplets. |
| Water is lost as the liquid. | Water is lost as the vapour. |
| Water lost in guttation is rich in minerals. | The transpired water is pure. |
| The process takes place through hydathodes. | The process takes place through stomata. |
| It is an uncontrolled phenomenon. | It is a controlled phenomenon. |
| Occurs in humid conditions. | Occurs under the dry conditions. |
| Occurs in herbaceous plants. | Occurs both in terrestrial and herbaceous plants. |
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