CBSE Biology Experiment- Study of the Rate of Respiration in Flower Buds/Leaf Tissue and Germinating Seeds
Plants respire all the time, whether it's light or dark, but only photosynthesise in daylight. Respiration is the opposite of photosynthesis in many ways. Only leaves and stems are involved during photosynthesis, but in respiration, roots, stems, and flower buds are involved as well. Respiration in plants is the process of breaking down glucose molecules formed during photosynthesis and producing energy. There is a difference in the rate of respiration between different tissues and organs. The process of respiration in the mitochondria occurs in the presence of oxygen, called aerobic respiration. Dark respiration and photorespiration are two types of respiration in plants.
Table of Content
The following article contains:
Aim
Theory
Procedure
Observations
Result
Precautions
Aim
To study the respiration rate in flowering buds.
Apparatus Required
Ganong’s respirometer:
Manometer
Bigger bulb with a stopper
Smaller bulb
Levelling tube attached to the manometer with a rubber tube
10% Potassium hydroxide solution
Flower buds, germinating seeds, and leaf tissue
Theory
During respiration, carbon dioxide is released into the atmosphere by living organisms. A respirometer measures this by using a sealed container with living specimens and a substance such as KOH to absorb the CO2. Manometry is used to measure oxygen uptake. A U-tube manometer is commonly used to measure the difference in pressure between a container and the atmosphere. An organism takes up O2, and CO2 is produced proportionally, but KOH absorbs all the CO2.
Ganong’s respirometer
Procedure
Take 2 ml of flower buds, leaf tissue, and germinating seeds and place them in the huge bulbs of three different respirometers.
Add 10% potassium hydroxide solution to the manometer tube.
At first, atmospheric air surrounding the respiratory material is moved to atmospheric pressure by regulating the bulb stopper. Regulation continues until the neck, and the hole coincide.
A reservoir tube on the right has been levelled so that the KOH solution inside the tube reaches the mark of 100 ml at the manometer's base.
Plant materials are now enclosed in a setup of 100 ml of air.
The experiment starts when you turn the glass stopper at the top of the bottle, cutting off the atmospheric air.
Take note of the changes that are occurring.
There should be a 10-minute interlude between the readings.
Observations
In the manometer tube, the solution eventually rises.
As aerial oxygen is 20%, all measurements for the experiment should be taken up to the 80 ml mark, i.e., volume: 20ml.
In both tubes, the liquid needs to reach the same point at all times, i.e., the closed tube must be under atmospheric pressure.
Carbon dioxide, which emerges from the respiring material used, can be measured in millimetres.
Observation for each sample is noted down and compared.
Result
KOH solution consumes the liberated carbon dioxide when it comes in contact with it. Since oxygen is absorbed into the manometer tube, the KOH solution rises.
The rate at which the KOH solution rises can be calculated by measuring the volume of oxygen consumed per unit time per 2ml of the respiring material during aerobic respiration.
The tissues with the highest respiratory activity are younger and actively growing meristematic tissues, and the lowest ones are mature tissues.
More quantity of protoplasm indicates a higher respiration rate.
It was found that the highest rate of respiration is found in flower buds when compared with leaves and germinating seeds.
Precautions
An airtight environment is required for all the experimental setup connections.
One should use freshly prepared potassium hydroxide solution.
Germinating seeds should be moistened during the experiment.
Lab Manual Questions
1. How do you define respiration in plants?
Ans. Respiration in plants is the process of breaking down glucose molecules formed during photosynthesis and producing energy.
2. Mention the reason for using the KOH solution in the respirometer.
Ans. Since KOH can absorb CO2, it is used in the respirometer.
3. Why did you take seeds in the germination stage instead of dry seeds?
Ans. Since germinating seeds actively grow, they show respiration faster than dry seeds.
4. What is the advantage of removing the seed coats in peas?
Ans. Since seed coats can slow the rate of gaseous exchange, removing them is better for enhancing respiration speed.
Viva Questions
1. In what condition does the rate of respiration increase in plants?
Ans. The respiration rate increases rapidly when damaged cells are replaced with new cells. Since this process needs a lot of energy to divide cells, respiration also increases.
2. Respiration rate is highest in which part of the plant?
Ans. The respiration rate is highest in the flower buds of plants.
3. What can be measured with the help of a manometer?
Ans. Atmospheric pressure can be measured with the help of a manometer.
4. How do you differentiate respiration from photosynthesis?
Ans. Photosynthesis uses carbon dioxide, whereas respiration evolves carbon dioxide. Photosynthesis takes place only in chloroplast-containing cells, whereas respiration takes place in all parts of the plants.
5. What happens to carbon dioxide and oxygen in respiration in plants?
Ans. Plants consume oxygen and release carbon dioxide into the atmosphere.
6. While carbon dioxide is released during respiration, the amount of CO2 in the atmosphere is the same. Why?
Ans. Because carbon dioxide released during the process of respiration is converted into sugar, which helps maintain the same amount of carbon dioxide in the atmosphere.
7. Which part of the plant carries cellular respiration?
Ans. Mitochondria carry out cellular respiration in plants.
8. Name four external factors affecting the rate of respiration in plants.
Ans. Light, temperature, injury, and water affect plants' respiration rate.
9. What are the applications of Ganong’s respirometer?
Ans. Ganong’s respirometer can be used to study the respiration rate in various parts of the plants, such as roots, leaves, seeds, and flower buds. The respiratory quotient can also be identified with this method.
10. What is the ‘respiratory quotient’?
Ans. The respiratory quotient is the ratio of the amount of carbon dioxide liberated over oxygen utilised in respiration.
Practical Based Questions
Name the solution used in the respirometer.
Sodium hydroxide
Potassium hydroxide
Magnesium hydroxide
Potassium chloride
Ans. B) Potassium hydroxide
Respiring material is placed in which part of the respirometer?
Bigger bulb
Levelling tube
Smaller bulb
Hole
Ans. C) Smaller bulb
More quantity of protoplasm indicates more
Respiration rate
Photosynthesis rate
Both respiration and photosynthesis rate
None of the above
Ans. A) Respiration rate
Respiration in plants takes place
Only in nights
Only in the daytime
On both day and night
Only in light
Ans. C) On both day and night
Which of the following parts shows more respiration?
Germinating seeds
Plant roots
Dry seeds
Leaves
Ans. A) Germinating seeds
Chlorophyll does not play any role in
Photorespiration
Respiration
Photosynthesis
All the above
Ans. B) Respiration
Respiration in plants is the opposite of
Digestion
Flowering
Germination
Photosynthesis
Ans. D) Photosynthesis
Why do you moisten germinating seeds?
Germinating seeds require moisture
If the moisture content is not available, seeds get dried
Respiration rate decreases with dryness of seeds
All the above
Ans. D) All the above
Which of the following is the tissue with the highest respiratory activity?
Meristematic tissue
Xylem
Phloem
Epidermis
Ans. A) Meristematic tissue
Photorespiration takes place in
Peroxisome
Chloroplast
Mitochondria
All the above
Ans. D) All the above
Conclusion
Respiration in plants is the process of breaking down glucose molecules formed during photosynthesis and producing energy. Using Ganong's respirometer, we can estimate the respiration rate in flower buds. The respiration rate is highest in plants' younger and actively growing meristematic tissues. Compared to other parts of the plant, the highest respiration rate is found in flower buds.
FAQs on To Study the Rate of Respiration in Flower Buds/Leaf Tissue and Germinating Seeds
1. What is the primary aim of the Class 11 Biology experiment on the rate of respiration in flower buds, leaf tissue, and germinating seeds?
The main aim of this experiment is to study and compare the relative rates of respiration in different plant tissues. It specifically investigates whether metabolically active tissues like germinating seeds and flower buds respire at a different rate than mature tissues like leaf tissue by measuring the volume of oxygen consumed over time.
2. Which plant tissues are expected to show the highest rate of respiration in this experiment, and what is the key reason for this?
Actively growing tissues, such as flower buds and germinating seeds, are expected to show the highest rate of respiration. This is because these tissues contain a high concentration of meristematic cells and dense protoplasm. They undergo rapid cell division and growth, processes that demand a significant amount of energy (ATP), which is produced through cellular respiration.
3. What is the specific function of the potassium hydroxide (KOH) solution in the setup of Ganong's respirometer?
The potassium hydroxide (KOH) solution is a strong alkali used to absorb the carbon dioxide (CO₂) gas that is released by the plant tissues during respiration. By removing CO₂ from the sealed apparatus, any measured decrease in gas volume can be attributed solely to the consumption of oxygen (O₂) by the respiring material.
4. Why are germinating seeds considered more suitable than dry seeds for demonstrating a high rate of respiration?
Germinating seeds are in a state of high metabolic activity. They actively break down stored food to fuel the growth of the embryo, a process that requires a large amount of energy and thus a very high rate of respiration. In contrast, dry seeds are in a dormant state with minimal metabolic activity and a negligible respiration rate, making them unsuitable for observing significant gas exchange in a short time frame.
5. For a 3-mark question, list three essential precautions that must be taken while performing the respiration rate experiment.
Three essential precautions to ensure accurate results in this experiment are:
- Airtight Apparatus: All connections in the respirometer setup must be completely sealed with vaseline or grease to prevent any leakage of gases.
- Fresh KOH Solution: A freshly prepared potassium hydroxide solution should be used as its ability to absorb CO₂ diminishes over time.
- Maintain Moisture: The germinating seeds or other plant tissues must be kept moist throughout the experiment to ensure they remain metabolically active and respire at a normal rate.
6. How does the experimental setup allow for the measurement of oxygen consumption when it is the carbon dioxide that gets absorbed?
The setup measures oxygen consumption indirectly. As the plant tissue respires, it consumes oxygen and releases carbon dioxide. The KOH solution immediately absorbs this released CO₂. Therefore, the net effect within the sealed tube is a decrease in the total volume of gas, which corresponds directly to the volume of oxygen consumed. This decrease in volume creates a partial vacuum, causing the coloured liquid in the manometer to rise, providing a measurable indication of oxygen uptake.
7. A student observes that flower buds show a higher rate of respiration than mature leaves. Provide two biological reasons to explain this finding.
A higher rate of respiration in flower buds compared to mature leaves can be attributed to:
- Higher Metabolic Activity: Flower buds are developing structures containing actively dividing meristematic tissues. The formation of floral parts is an energy-intensive process requiring high rates of respiration. Mature leaves have completed their growth and have a lower basal metabolic rate.
- Protoplasm Density: Cells in young, growing tissues like flower buds have denser protoplasm and a smaller central vacuole compared to mature leaf cells. A greater amount of protoplasm is directly correlated with a higher rate of cellular respiration.
8. What is the Respiratory Quotient (RQ), and is it possible to measure it using Ganong's respirometer as set up for this experiment?
The Respiratory Quotient (RQ) is the ratio of the volume of carbon dioxide released to the volume of oxygen consumed during respiration (RQ = CO₂ / O₂). It is not possible to measure RQ with the standard setup of this experiment because the potassium hydroxide (KOH) absorbs all the CO₂ produced. To determine RQ, one would need to conduct a parallel experiment without KOH to measure the net change in gas volume and then compare it with the results from the experiment with KOH.
9. What are two key limitations of using an apparatus like Ganong's respirometer for studying plant respiration?
Two key limitations are:
- Sensitivity to Environmental Changes: The apparatus is highly sensitive to fluctuations in ambient temperature and atmospheric pressure, which can cause changes in gas volume and lead to inaccurate readings if not properly controlled for.
- Only for Aerobic Respiration: This method measures the rate of aerobic respiration by tracking oxygen consumption. It cannot be used to study or measure the rate of anaerobic respiration, where oxygen is not consumed.
