To Study 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

1. Take 2 ml of flower buds, leaf tissue, and germinating seeds and place them in the huge bulbs of three different respirometers.

2. Add 10% potassium hydroxide solution to the manometer tube.

3. 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.

4. 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.

5. Plant materials are now enclosed in a setup of 100 ml of air.

6. The experiment starts when you turn the glass stopper at the top of the bottle, cutting off the atmospheric air.

7. Take note of the changes that are occurring.

8. 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

1. Name the solution used in the respirometer.

1. Sodium hydroxide

2. Potassium hydroxide

3. Magnesium hydroxide

4. Potassium chloride

Ans. B) Potassium hydroxide

2. Respiring material is placed in which part of the respirometer?

1. Bigger bulb

2. Levelling tube

3. Smaller bulb

4. Hole

Ans. C) Smaller bulb

3. More quantity of protoplasm indicates more

1. Respiration rate

2. Photosynthesis rate

3. Both respiration and photosynthesis rate

4. None of the above

Ans. A) Respiration rate

4. Respiration in plants takes place

1. Only in nights

2. Only in the daytime

3. On both day and night

4. Only in light

Ans. C) On both day and night

5. Which of the following parts shows more respiration?

1. Germinating seeds

2. Plant roots

3. Dry seeds

4. Leaves

Ans. A) Germinating seeds

6. Chlorophyll does not play any role in

1. Photorespiration

2. Respiration

3. Photosynthesis

4. All the above

Ans. B) Respiration

7. Respiration in plants is the opposite of

1. Digestion

2. Flowering

3. Germination

4. Photosynthesis

Ans. D) Photosynthesis

8. Why do you moisten germinating seeds?

1. Germinating seeds require moisture

2. If the moisture content is not available, seeds get dried

3. Respiration rate decreases with dryness of seeds

4. All the above

Ans. D) All the above

9. Which of the following is the tissue with the highest respiratory activity?

1. Meristematic tissue

2. Xylem

3. Phloem

4. Epidermis

Ans. A) Meristematic tissue

10. Photorespiration takes place in

1. Peroxisome 

2. Chloroplast

3. Mitochondria

4. 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.